NOTICE This repository contains the public FTC SDK for the SKYSTONE (2019-2020) competition season. If you are looking for the current season's FTC SDK software, please visit the new and permanent home of the public FTC SDK: FtcRobotController repository Welcome! This GitHub repository contains the source code that is used to build an Android app to control a FIRST Tech Challenge competition robot. To use this SDK, download/clone the entire project to your local computer. Getting Started If you are new to robotics or new to the FIRST Tech Challenge, then you should consider reviewing the FTC Blocks Tutorial to get familiar with how to use the control system: FTC Blocks Online Tutorial Even if you are an advanced Java programmer, it is helpful to start with the FTC Blocks tutorial, and then migrate to the OnBot Java Tool or to Android Studio afterwards. Downloading the Project If you are an Android Studio programmer, there are several ways to download this repo. Note that if you use the Blocks or OnBot Java Tool to program your robot, then you do not need to download this repository. If you are a git user, you can clone the most current version of the repository: git clone https://github.com/FIRST-Tech-Challenge/SKYSTONE.git Or, if you prefer, you can use the "Download Zip" button available through the main repository page. Downloading the project as a .ZIP file will keep the size of the download manageable. You can also download the project folder (as a .zip or .tar.gz archive file) from the Downloads subsection of the Releases page for this repository. Once you have downloaded and uncompressed (if needed) your folder, you can use Android Studio to import the folder ("Import project (Eclipse ADT, Gradle, etc.)"). Getting Help User Documentation and Tutorials FIRST maintains online documentation with information and tutorials on how to use the FIRST Tech Challenge software and robot control system. You can access this documentation using the following link: SKYSTONE Online Documentation Note that the online documentation is an "evergreen" document that is constantly being updated and edited. It contains the most current information about the FIRST Tech Challenge software and control system. Javadoc Reference Material The Javadoc reference documentation for the FTC SDK is now available online. Click on the following link to view the FTC SDK Javadoc documentation as a live website: FTC Javadoc Documentation Documentation for the FTC SDK is also included with this repository. There is a subfolder called "doc" which contains several subfolders: The folder "apk" contains the .apk files for the FTC Driver Station and FTC Robot Controller apps. The folder "javadoc" contains the JavaDoc user documentation for the FTC SDK. Online User Forum For technical questions regarding the Control System or the FTC SDK, please visit the FTC Technology forum: FTC Technology Forum Release Information Version 5.5 (20200824-090813) Version 5.5 requires Android Studio 4.0 or later. New features Adds support for calling custom Java classes from Blocks OpModes (fixes SkyStone issue #161). Classes must be in the org.firstinspires.ftc.teamcode package. Methods must be public static and have no more than 21 parameters. Parameters declared as OpMode, LinearOpMode, Telemetry, and HardwareMap are supported and the argument is provided automatically, regardless of the order of the parameters. On the block, the sockets for those parameters are automatically filled in. Parameters declared as char or java.lang.Character will accept any block that returns text and will only use the first character in the text. Parameters declared as boolean or java.lang.Boolean will accept any block that returns boolean. Parameters declared as byte, java.lang.Byte, short, java.lang.Short, int, java.lang.Integer, long, or java.lang.Long, will accept any block that returns a number and will round that value to the nearest whole number. Parameters declared as float, java.lang.Float, double, java.lang.Double will accept any block that returns a number. Adds telemetry API method for setting display format Classic Monospace HTML (certain tags only) Adds blocks support for switching cameras. Adds Blocks support for TensorFlow Object Detection with a custom model. Adds support for uploading a custom TensorFlow Object Detection model in the Manage page, which is especially useful for Blocks and OnBotJava users. Shows new Control Hub blink codes when the WiFi band is switched using the Control Hub's button (only possible on Control Hub OS 1.1.2) Adds new warnings which can be disabled in the Advanced RC Settings Mismatched app versions warning Unnecessary 2.4 GHz WiFi usage warning REV Hub is running outdated firmware (older than version 1.8.2) Adds support for Sony PS4 gamepad, and reworks how gamepads work on the Driver Station Removes preference which sets gamepad type based on driver position. Replaced with menu which allows specifying type for gamepads with unknown VID and PID Attempts to auto-detect gamepad type based on USB VID and PID If gamepad VID and PID is not known, use type specified by user for that VID and PID If gamepad VID and PID is not known AND the user has not specified a type for that VID and PID, an educated guess is made about how to map the gamepad Driver Station will now attempt to automatically recover from a gamepad disconnecting, and re-assign it to the position it was assigned to when it dropped If only one gamepad is assigned and it drops: it can be recovered If two gamepads are assigned, and have different VID/PID signatures, and only one drops: it will be recovered If two gamepads are assigned, and have different VID/PID signatures, and BOTH drop: both will be recovered If two gamepads are assigned, and have the same VID/PID signatures, and only one drops: it will be recovered If two gamepads are assigned, and have the same VID/PID signatures, and BOTH drop: neither will be recovered, because of the ambiguity of the gamepads when they re-appear on the USB bus. There is currently one known edge case: if there are two gamepads with the same VID/PID signature plugged in, but only one is assigned, and they BOTH drop, it's a 50-50 chance of which one will be chosen for automatic recovery to the assigned position: it is determined by whichever one is re-enumerated first by the USB bus controller. Adds landscape user interface to Driver Station New feature: practice timer with audio cues New feature (Control Hub only): wireless network connection strength indicator (0-5 bars) New feature (Control Hub only): tapping on the ping/channel display will switch to an alternate display showing radio RX dBm and link speed (tap again to switch back) The layout will NOT autorotate. You can switch the layout from the Driver Station's settings menu. Breaking changes Removes support for Android versions 4.4 through 5.1 (KitKat and Lollipop). The minSdkVersion is now 23. Removes the deprecated LinearOpMode methods waitOneFullHardwareCycle() and waitForNextHardwareCycle() Enhancements Handles RS485 address of Control Hub automatically The Control Hub is automatically given a reserved address Existing configuration files will continue to work All addresses in the range of 1-10 are still available for Expansion Hubs The Control Hub light will now normally be solid green, without blinking to indicate the address The Control Hub will not be shown on the Expansion Hub Address Change settings page Improves REV Hub firmware updater The user can now choose between all available firmware update files Version 1.8.2 of the REV Hub firmware is bundled into the Robot Controller app. Text was added to clarify that Expansion Hubs can only be updated via USB. Firmware update speed was reduced to improve reliability Allows REV Hub firmware to be updated directly from the Manage webpage Improves log viewer on Robot Controller Horizontal scrolling support (no longer word wrapped) Supports pinch-to-zoom Uses a monospaced font Error messages are highlighted New color scheme Attempts to force-stop a runaway/stuck OpMode without restarting the entire app Not all types of runaway conditions are stoppable, but if the user code attempts to talk to hardware during the runaway, the system should be able to capture it. Makes various tweaks to the Self Inspect screen Renames "OS version" entry to "Android version" Renames "WiFi Direct Name" to "WiFi Name" Adds Control Hub OS version, when viewing the report of a Control Hub Hides the airplane mode entry, when viewing the report of a Control Hub Removes check for ZTE Speed Channel Changer Shows firmware version for all Expansion and Control Hubs Reworks network settings portion of Manage page All network settings are now applied with a single click The WiFi Direct channel of phone-based Robot Controllers can now be changed from the Manage page WiFi channels are filtered by band (2.4 vs 5 GHz) and whether they overlap with other channels The current WiFi channel is pre-selected on phone-based Robot Controllers, and Control Hubs running OS 1.1.2 or later. On Control Hubs running OS 1.1.2 or later, you can choose to have the system automatically select a channel on the 5 GHz band Improves OnBotJava New light and dark themes replace the old themes (chaos, github, chrome,...) the new default theme is light and will be used when you first update to this version OnBotJava now has a tabbed editor Read-only offline mode Improves function of "exit" menu item on Robot Controller and Driver Station Now guaranteed to be fully stopped and unloaded from memory Shows a warning message if a LinearOpMode exists prematurely due to failure to monitor for the start condition Improves error message shown when the Driver Station and Robot Controller are incompatible with each other Driver Station OpMode Control Panel now disabled while a Restart Robot is in progress Disables advanced settings related to WiFi direct when the Robot Controller is a Control Hub. Tint phone battery icons on Driver Station when low/critical. Uses names "Control Hub Portal" and "Control Hub" (when appropriate) in new configuration files Improve I2C read performance Very large improvement on Control Hub; up to ~2x faster with small (e.g. 6 byte) reads Not as apparent on Expansion Hubs connected to a phone Update/refresh build infrastructure Update to 'androidx' support library from 'com.android.support:appcompat', which is end-of-life Update targetSdkVersion and compileSdkVersion to 28 Update Android Studio's Android plugin to latest Fix reported build timestamp in 'About' screen Add sample illustrating manual webcam use: ConceptWebcam Bug fixes Fixes SkyStone issue #248 Fixes SkyStone issue #232 and modifies bulk caching semantics to allow for cache-preserving MANUAL/AUTO transitions. Improves performance when REV 2M distance sensor is unplugged Improves readability of Toast messages on certain devices Allows a Driver Station to connect to a Robot Controller after another has disconnected Improves generation of fake serial numbers for UVC cameras which do not provide a real serial number Previously some devices would assign such cameras a serial of 0:0 and fail to open and start streaming Fixes ftc_app issue #638. Fixes a slew of bugs with the Vuforia camera monitor including: Fixes bug where preview could be displayed with a wonky aspect ratio Fixes bug where preview could be cut off in landscape Fixes bug where preview got totally messed up when rotating phone Fixes bug where crosshair could drift off target when using webcams Fixes issue in UVC driver on some devices (ftc_app 681) if streaming was started/stopped multiple times in a row Issue manifested as kernel panic on devices which do not have this kernel patch. On affected devices which do have the patch, the issue was manifest as simply a failure to start streaming. The Tech Team believes that the root cause of the issue is a bug in the Linux kernel XHCI driver. A workaround was implemented in the SDK UVC driver. Fixes bug in UVC driver where often half the frames from the camera would be dropped (e.g. only 15FPS delivered during a streaming session configured for 30FPS). Fixes issue where TensorFlow Object Detection would show results whose confidence was lower than the minimum confidence parameter. Fixes a potential exploitation issue of CVE-2019-11358 in OnBotJava Fixes changing the address of an Expansion Hub with additional Expansion Hubs connected to it Preserves the Control Hub's network connection when "Restart Robot" is selected Fixes issue where device scans would fail while the Robot was restarting Fix RenderScript usage Use androidx.renderscript variant: increased compatibility Use RenderScript in Java mode, not native: simplifies build Fixes webcam-frame-to-bitmap conversion problem: alpha channel wasn't being initialized, only R, G, & B Fixes possible arithmetic overflow in Deadline Fixes deadlock in Vuforia webcam support which could cause 5-second delays when stopping OpMode Version 5.4 (20200108-101156) Fixes SkyStone issue #88 Adds an inspection item that notes when a robot controller (Control Hub) is using the factory default password. Fixes SkyStone issue #61 Fixes SkyStone issue #142 Fixes ftc_app issue #417 by adding more current and voltage monitoring capabilities for REV Hubs. Fixes a crash sometimes caused by OnBotJava activity Improves OnBotJava autosave functionality ftc_app #738 Fixes system responsiveness issue when an Expansion Hub is disconnected Fixes issue where IMU initialization could prevent Op Modes from stopping Fixes issue where AndroidTextToSpeech.speak() would fail if it was called too early Adds telemetry.speak() methods and blocks, which cause the Driver Station (if also updated) to speak text Adds and improves Expansion Hub-related warnings Improves Expansion Hub low battery warning Displays the warning immediately after the hub reports it Specifies whether the condition is current or occurred temporarily during an OpMode run Displays which hubs reported low battery Displays warning when hub loses and regains power during an OpMode run Fixes the hub's LED pattern after this condition Displays warning when Expansion Hub is not responding to commands Specifies whether the condition is current or occurred temporarily during an OpMode run Clarifies warning when Expansion Hub is not present at startup Specifies that this condition requires a Robot Restart before the hub can be used. The hub light will now accurately reflect this state Improves logging and reduces log spam during these conditions Syncs the Control Hub time and timezone to a connected web browser programming the robot, if a Driver Station is not available. Adds bulk read functionality for REV Hubs A bulk caching mode must be set at the Hub level with LynxModule#setBulkCachingMode(). This applies to all relevant SDK hardware classes that reference that Hub. The following following Hub bulk caching modes are available: BulkCachingMode.OFF (default): All hardware calls operate as usual. Bulk data can read through LynxModule#getBulkData() and processed manually. BulkCachingMode.AUTO: Applicable hardware calls are served from a bulk read cache that is cleared/refreshed automatically to ensure identical commands don't hit the same cache. The cache can also be cleared manually with LynxModule#clearBulkCache(), although this is not recommended. (advanced users) BulkCachingMode.MANUAL: Same as BulkCachingMode.AUTO except the cache is never cleared automatically. To avoid getting stale data, the cache must be manually cleared at the beginning of each loop body or as the user deems appropriate. Removes PIDF Annotation values added in Rev 5.3 (to AndyMark, goBILDA and TETRIX motor configurations). The new motor types will still be available but their Default control behavior will revert back to Rev 5.2 Adds new ConceptMotorBulkRead sample Opmode to demonstrate and compare Motor Bulk-Read modes for reducing I/O latencies. Version 5.3 (20191004-112306) Fixes external USB/UVC webcam support Makes various bugfixes and improvements to Blocks page, including but not limited to: Many visual tweaks Browser zoom and window resize behave better Resizing the Java preview pane works better and more consistently across browsers The Java preview pane consistently gets scrollbars when needed The Java preview pane is hidden by default on phones Internet Explorer 11 should work Large dropdown lists display properly on lower res screens Disabled buttons are now visually identifiable as disabled A warning is shown if a user selects a TFOD sample, but their device is not compatible Warning messages in a Blocks op mode are now visible by default. Adds goBILDA 5201 and 5202 motors to Robot Configurator Adds PIDF Annotation values to AndyMark, goBILDA and TETRIX motor configurations. This has the effect of causing the RUN_USING_ENCODERS and RUN_TO_POSITION modes to use PIDF vs PID closed loop control on these motors. This should provide more responsive, yet stable, speed control. PIDF adds Feedforward control to the basic PID control loop. Feedforward is useful when controlling a motor's speed because it "anticipates" how much the control voltage must change to achieve a new speed set-point, rather than requiring the integrated error to change sufficiently. The PIDF values were chosen to provide responsive, yet stable, speed control on a lightly loaded motor. The more heavily a motor is loaded (drag or friction), the more noticable the PIDF improvement will be. Fixes startup crash on Android 10 Fixes ftc_app issue #712 (thanks to FROGbots-4634) Fixes ftc_app issue #542 Allows "A" and lowercase letters when naming device through RC and DS apps. Version 5.2 (20190905-083277) Fixes extra-wide margins on settings activities, and placement of the new configuration button Adds Skystone Vuforia image target data. Includes sample Skystone Vuforia Navigation op modes (Java). Includes sample Skystone Vuforia Navigation op modes (Blocks). Adds TensorFlow inference model (.tflite) for Skystone game elements. Includes sample Skystone TensorFlow op modes (Java). Includes sample Skystone TensorFlow op modes (Blocks). Removes older (season-specific) sample op modes. Includes 64-bit support (to comply with Google Play requirements). Protects against Stuck OpModes when a Restart Robot is requested. (Thanks to FROGbots-4634) (ftc_app issue #709) Blocks related changes: Fixes bug with blocks generated code when hardware device name is a java or javascript reserved word. Shows generated java code for blocks, even when hardware items are missing from the active configuration. Displays warning icon when outdated Vuforia and TensorFlow blocks are used (SkyStone issue #27) Version 5.1 (20190820-222104) Defines default PIDF parameters for the following motors: REV Core Hex Motor REV 20:1 HD Hex Motor REV 40:1 HD Hex Motor Adds back button when running on a device without a system back button (such as a Control Hub) Allows a REV Control Hub to update the firmware on a REV Expansion Hub via USB Fixes SkyStone issue #9 Fixes ftc_app issue #715 Prevents extra DS User clicks by filtering based on current state. Prevents incorrect DS UI state changes when receiving new OpMode list from RC Adds support for REV Color Sensor V3 Adds a manual-refresh DS Camera Stream for remotely viewing RC camera frames. To show the stream on the DS, initialize but do not run a stream-enabled opmode, select the Camera Stream option in the DS menu, and tap the image to refresh. This feature is automatically enabled when using Vuforia or TFOD—no additional RC configuration is required for typical use cases. To hide the stream, select the same menu item again. Note that gamepads are disabled and the selected opmode cannot be started while the stream is open as a safety precaution. To use custom streams, consult the API docs for CameraStreamServer#setSource and CameraStreamSource. Adds many Star Wars sounds to RobotController resources. Added SKYSTONE Sounds Chooser Sample Program. Switches out startup, connect chimes, and error/warning sounds for Star Wars sounds Updates OnBot Java to use a WebSocket for communication with the robot The OnBot Java page no longer has to do a full refresh when a user switches from editing one file to another Known issues: Camera Stream The Vuforia camera stream inherits the issues present in the phone preview (namely ftc_app issue #574). This problem does not affect the TFOD camera stream even though it receives frames from Vuforia. The orientation of the stream frames may not always match the phone preview. For now, these frames may be rotated manually via a custom CameraStreamSource if desired. OnBotJava Browser back button may not always work correctly It's possible for a build to be queued, but not started. The OnBot Java build console will display a warning if this occurs. A user might not realize they are editing a different file if the user inadvertently switches from one file to another since this switch is now seamless. The name of the currently open file is displayed in the browser tab. Version 5.0 (built on 19.06.14) Support for the REV Robotics Control Hub. Adds a Java preview pane to the Blocks editor. Adds a new offline export feature to the Blocks editor. Display wifi channel in Network circle on Driver Station. Adds calibration for Logitech C270 Updates build tooling and target SDK. Compliance with Google's permissions infrastructure (Required after build tooling update). Keep Alives to mitigate the Motorola wifi scanning problem. Telemetry substitute no longer necessary. Improves Vuforia error reporting. Fixes ftctechnh/ftc_app issues 621, 713. Miscellaneous bug fixes and improvements. Version 4.3 (built on 18.10.31) Includes missing TensorFlow-related libraries and files. Version 4.2 (built on 18.10.30) Includes fix to avoid deadlock situation with WatchdogMonitor which could result in USB communication errors. Comm error appeared to require that user disconnect USB cable and restart the Robot Controller app to recover. robotControllerLog.txt would have error messages that included the words "E RobotCore: lynx xmit lock: #### abandoning lock:" Includes fix to correctly list the parent module address for a REV Robotics Expansion Hub in a configuration (.xml) file. Bug in versions 4.0 and 4.1 would incorrect list the address module for a parent REV Robotics device as "1". If the parent module had a higher address value than the daisy-chained module, then this bug would prevent the Robot Controller from communicating with the downstream Expansion Hub. Added requirement for ACCESS_COARSE_LOCATION to allow a Driver Station running Android Oreo to scan for Wi-Fi Direct devices. Added google() repo to build.gradle because aapt2 must be downloaded from the google() repository beginning with version 3.2 of the Android Gradle Plugin. Important Note: Android Studio users will need to be connected to the Internet the first time build the ftc_app project. Internet connectivity is required for the first build so the appropriate files can be downloaded from the Google repository. Users should not need to be connected to the Internet for subsequent builds. This should also fix buid issue where Android Studio would complain that it "Could not find com.android.tools.lint:lint-gradle:26.1.4" (or similar). Added support for REV Spark Mini motor controller as part of the configuration menu for a servo/PWM port on the REV Expansion Hub. Provide examples for playing audio files in an Op Mode. Block Development Tool Changes Includes a fix for a problem with the Velocity blocks that were reported in the FTC Technology forum (Blocks Programming subforum). Change the "Save completed successfully." message to a white color so it will contrast with a green background. Fixed the "Download image" feature so it will work if there are text blocks in the op mode. Introduce support for Google's TensorFlow Lite technology for object detetion for 2018-2019 game. TensorFlow lite can recognize Gold Mineral and Silver Mineral from 2018-2019 game. Example Java and Block op modes are included to show how to determine the relative position of the gold block (left, center, right). Version 4.1 (released on 18.09.24) Changes include: Fix to prevent crash when deprecated configuration annotations are used. Change to allow FTC Robot Controller APK to be auto-updated using FIRST Global Control Hub update scripts. Removed samples for non supported / non legal hardware. Improvements to Telemetry.addData block with "text" socket. Updated Blocks sample op mode list to include Rover Ruckus Vuforia example. Update SDK library version number. Version 4.0 (released on 18.09.12) Changes include: Initial support for UVC compatible cameras If UVC camera has a unique serial number, RC will detect and enumerate by serial number. If UVC camera lacks a unique serial number, RC will only support one camera of that type connected. Calibration settings for a few cameras are included (see TeamCode/src/main/res/xml/teamwebcamcalibrations.xml for details). User can upload calibration files from Program and Manage web interface. UVC cameras seem to draw a fair amount of electrical current from the USB bus. This does not appear to present any problems for the REV Robotics Control Hub. This does seem to create stability problems when using some cameras with an Android phone-based Robot Controller. FTC Tech Team is investigating options to mitigate this issue with the phone-based Robot Controllers. Updated sample Vuforia Navigation and VuMark Op Modes to demonstrate how to use an internal phone-based camera and an external UVC webcam. Support for improved motor control. REV Robotics Expansion Hub firmware 1.8 and greater will support a feed forward mechanism for closed loop motor control. FTC SDK has been modified to support PIDF coefficients (proportional, integral, derivative, and feed forward). FTC Blocks development tool modified to include PIDF programming blocks. Deprecated older PID-related methods and variables. REV's 1.8.x PIDF-related changes provide a more linear and accurate way to control a motor. Wireless Added 5GHz support for wireless channel changing for those devices that support it. Tested with Moto G5 and E4 phones. Also tested with other (currently non-approved) phones such as Samsung Galaxy S8. Improved Expansion Hub firmware update support in Robot Controller app Changes to make the system more robust during the firmware update process (when performed through Robot Controller app). User no longer has to disconnect a downstream daisy-chained Expansion Hub when updating an Expansion Hub's firmware. If user is updating an Expansion Hub's firmware through a USB connection, he/she does not have to disconnect RS485 connection to other Expansion Hubs. The user still must use a USB connection to update an Expansion Hub's firmware. The user cannot update the Expansion Hub firmware for a downstream device that is daisy chained through an RS485 connection. If an Expansion Hub accidentally gets "bricked" the Robot Controller app is now more likely to recognize the Hub when it scans the USB bus. Robot Controller app should be able to detect an Expansion Hub, even if it accidentally was bricked in a previous update attempt. Robot Controller app should be able to install the firmware onto the Hub, even if if accidentally was bricked in a previous update attempt. Resiliency FTC software can detect and enable an FTDI reset feature that is available with REV Robotics v1.8 Expansion Hub firmware and greater. When enabled, the Expansion Hub can detect if it hasn't communicated with the Robot Controller over the FTDI (USB) connection. If the Hub hasn't heard from the Robot Controller in a while, it will reset the FTDI connection. This action helps system recover from some ESD-induced disruptions. Various fixes to improve reliability of FTC software. Blocks Fixed errors with string and list indices in blocks export to java. Support for USB connected UVC webcams. Refactored optimized Blocks Vuforia code to support Rover Ruckus image targets. Added programming blocks to support PIDF (proportional, integral, derivative and feed forward) motor control. Added formatting options (under Telemetry and Miscellaneous categories) so user can set how many decimal places to display a numerical value. Support to play audio files (which are uploaded through Blocks web interface) on Driver Station in addition to the Robot Controller. Fixed bug with Download Image of Blocks feature. Support for REV Robotics Blinkin LED Controller. Support for REV Robotics 2m Distance Sensor. Added support for a REV Touch Sensor (no longer have to configure as a generic digital device). Added blocks for DcMotorEx methods. These are enhanced methods that you can use when supported by the motor controller hardware. The REV Robotics Expansion Hub supports these enhanced methods. Enhanced methods include methods to get/set motor velocity (in encoder pulses per second), get/set PIDF coefficients, etc.. Modest Improvements in Logging Decrease frequency of battery checker voltage statements. Removed non-FTC related log statements (wherever possible). Introduced a "Match Logging" feature. Under "Settings" a user can enable/disable this feature (it's disabled by default). If enabled, user provides a "Match Number" through the Driver Station user interface (top of the screen). The Match Number is used to create a log file specifically with log statements from that particular Op Mode run. Match log files are stored in /sdcard/FIRST/matlogs on the Robot Controller. Once an op mode run is complete, the Match Number is cleared. This is a convenient way to create a separate match log with statements only related to a specific op mode run. New Devices Support for REV Robotics Blinkin LED Controller. Support for REV Robotics 2m Distance Sensor. Added configuration option for REV 20:1 HD Hex Motor. Added support for a REV Touch Sensor (no longer have to configure as a generic digital device). Miscellaneous Fixed some errors in the definitions for acceleration and velocity in our javadoc documentation. Added ability to play audio files on Driver Station When user is configuring an Expansion Hub, the LED on the Expansion Hub will change blink pattern (purple-cyan) to indicate which Hub is currently being configured. Renamed I2cSensorType to I2cDeviceType. Added an external sample Op Mode that demonstrates localization using 2018-2019 (Rover Ruckus presented by QualComm) Vuforia targets. Added an external sample Op Mode that demonstrates how to use the REV Robotics 2m Laser Distance Sensor. Added an external sample Op Mode that demonstrates how to use the REV Robotics Blinkin LED Controller. Re-categorized external Java sample Op Modes to "TeleOp" instead of "Autonomous". Known issues: Initial support for UVC compatible cameras UVC cameras seem to draw significant amount of current from the USB bus. This does not appear to present any problems for the REV Robotics Control Hub. This does seem to create stability problems when using some cameras with an Android phone-based Robot Controller. FTC Tech Team is investigating options to mitigate this issue with the phone-based Robot Controllers. There might be a possible deadlock which causes the RC to become unresponsive when using a UVC webcam with a Nougat Android Robot Controller. Wireless When user selects a wireless channel, this channel does not necessarily persist if the phone is power cycled. Tech Team is hoping to eventually address this issue in a future release. Issue has been present since apps were introduced (i.e., it is not new with the v4.0 release). Wireless channel is not currently displayed for WiFi Direct connections. Miscellaneous The blink indication feature that shows which Expansion Hub is currently being configured does not work for a newly created configuration file. User has to first save a newly created configuration file and then close and re-edit the file in order for blink indicator to work. Version 3.6 (built on 17.12.18) Changes include: Blocks Changes Uses updated Google Blockly software to allow users to edit their op modes on Apple iOS devices (including iPad and iPhone). Improvement in Blocks tool to handle corrupt op mode files. Autonomous op modes should no longer get switched back to tele-op after re-opening them to be edited. The system can now detect type mismatches during runtime and alert the user with a message on the Driver Station. Updated javadoc documentation for setPower() method to reflect correct range of values (-1 to +1). Modified VuforiaLocalizerImpl to allow for user rendering of frames Added a user-overrideable onRenderFrame() method which gets called by the class's renderFrame() method. Version 3.5 (built on 17.10.30) Changes with version 3.5 include: Introduced a fix to prevent random op mode stops, which can occur after the Robot Controller app has been paused and then resumed (for example, when a user temporarily turns off the display of the Robot Controller phone, and then turns the screen back on). Introduced a fix to prevent random op mode stops, which were previously caused by random peer disconnect events on the Driver Station. Fixes issue where log files would be closed on pause of the RC or DS, but not re-opened upon resume. Fixes issue with battery handler (voltage) start/stop race. Fixes issue where Android Studio generated op modes would disappear from available list in certain situations. Fixes problem where OnBot Java would not build on REV Robotics Control Hub. Fixes problem where OnBot Java would not build if the date and time on the Robot Controller device was "rewound" (set to an earlier date/time). Improved error message on OnBot Java that occurs when renaming a file fails. Removed unneeded resources from android.jar binaries used by OnBot Java to reduce final size of Robot Controller app. Added MR_ANALOG_TOUCH_SENSOR block to Blocks Programming Tool. Version 3.4 (built on 17.09.06) Changes with version 3.4 include: Added telemetry.update() statement for BlankLinearOpMode template. Renamed sample Block op modes to be more consistent with Java samples. Added some additional sample Block op modes. Reworded OnBot Java readme slightly. Version 3.3 (built on 17.09.04) This version of the software includes improves for the FTC Blocks Programming Tool and the OnBot Java Programming Tool. Changes with verion 3.3 include: Android Studio ftc_app project has been updated to use Gradle Plugin 2.3.3. Android Studio ftc_app project is already using gradle 3.5 distribution. Robot Controller log has been renamed to /sdcard/RobotControllerLog.txt (note that this change was actually introduced w/ v3.2). Improvements in I2C reliability. Optimized I2C read for REV Expansion Hub, with v1.7 firmware or greater. Updated all external/samples (available through OnBot and in Android project folder). Vuforia Added support for VuMarks that will be used for the 2017-2018 season game. Blocks Update to latest Google Blockly release. Sample op modes can be selected as a template when creating new op mode. Fixed bug where the blocks would disappear temporarily when mouse button is held down. Added blocks for Range.clip and Range.scale. User can now disable/enable Block op modes. Fix to prevent occasional Blocks deadlock. OnBot Java Significant improvements with autocomplete function for OnBot Java editor. Sample op modes can be selected as a template when creating new op mode. Fixes and changes to complete hardware setup feature. Updated (and more useful) onBot welcome message. Known issues: Android Studio After updating to the new v3.3 Android Studio project folder, if you get error messages indicating "InvalidVirtualFileAccessException" then you might need to do a File->Invalidate Caches / Restart to clear the error. OnBot Java Sometimes when you push the build button to build all op modes, the RC returns an error message that the build failed. If you press the build button a second time, the build typically suceeds. Version 3.2 (built on 17.08.02) This version of the software introduces the "OnBot Java" Development Tool. Similar to the FTC Blocks Development Tool, the FTC OnBot Java Development Tool allows a user to create, edit and build op modes dynamically using only a Javascript-enabled web browser. The OnBot Java Development Tool is an integrated development environment (IDE) that is served up by the Robot Controller. Op modes are created and edited using a Javascript-enabled browser (Google Chromse is recommended). Op modes are saved on the Robot Controller Android device directly. The OnBot Java Development Tool provides a Java programming environment that does NOT need Android Studio. Changes with version 3.2 include: Enhanced web-based development tools Introduction of OnBot Java Development Tool. Web-based programming and management features are "always on" (user no longer needs to put Robot Controller into programming mode). Web-based management interface (where user can change Robot Controller name and also easily download Robot Controller log file). OnBot Java, Blocks and Management features available from web based interface. Blocks Programming Development Tool: Changed "LynxI2cColorRangeSensor" block to "REV Color/range sensor" block. Fixed tooltip for ColorSensor.isLightOn block. Added blocks for ColorSensor.getNormalizedColors and LynxI2cColorRangeSensor.getNormalizedColors. Added example op modes for digital touch sensor and REV Robotics Color Distance sensor. User selectable color themes. Includes many minor enhancements and fixes (too numerous to list). Known issues: Auto complete function is incomplete and does not support the following (for now): Access via this keyword Access via super keyword Members of the super cloass, not overridden by the class Any methods provided in the current class Inner classes Can't handle casted objects Any objects coming from an parenthetically enclosed expression Version 3.10 (built on 17.05.09) This version of the software provides support for the REV Robotics Expansion Hub. This version also includes improvements in the USB communication layer in an effort to enhance system resiliency. If you were using a 2.x version of the software previously, updating to version 3.1 requires that you also update your Driver Station software in addition to updating the Robot Controller software. Also note that in version 3.10 software, the setMaxSpeed and getMaxSpeed methods are no longer available (not deprecated, they have been removed from the SDK). Also note that the the new 3.x software incorporates motor profiles that a user can select as he/she configures the robot. Changes include: Blocks changes Added VuforiaTrackableDefaultListener.getPose and Vuforia.trackPose blocks. Added optimized blocks support for Vuforia extended tracking. Added atan2 block to the math category. Added useCompetitionFieldTargetLocations parameter to Vuforia.initialize block. If set to false, the target locations are placed at (0,0,0) with target orientation as specified in https://github.com/gearsincorg/FTCVuforiaDemo/blob/master/Robot_Navigation.java tutorial op mode. Incorporates additional improvements to USB comm layer to improve system resiliency (to recover from a greater number of communication disruptions). Additional Notes Regarding Version 3.00 (built on 17.04.13) In addition to the release changes listed below (see section labeled "Version 3.00 (built on 17.04.013)"), version 3.00 has the following important changes: Version 3.00 software uses a new version of the FTC Robocol (robot protocol). If you upgrade to v3.0 on the Robot Controller and/or Android Studio side, you must also upgrade the Driver Station software to match the new Robocol. Version 3.00 software removes the setMaxSpeed and getMaxSpeed methods from the DcMotor class. If you have an op mode that formerly used these methods, you will need to remove the references/calls to these methods. Instead, v3.0 provides the max speed information through the use of motor profiles that are selected by the user during robot configuration. Version 3.00 software currently does not have a mechanism to disable extra i2c sensors. We hope to re-introduce this function with a release in the near future. Version 3.00 (built on 17.04.13) *** Use this version of the software at YOUR OWN RISK!!! *** This software is being released as an "alpha" version. Use this version at your own risk! This pre-release software contains SIGNIFICANT changes, including changes to the Wi-Fi Direct pairing mechanism, rewrites of the I2C sensor classes, changes to the USB/FTDI layer, and the introduction of support for the REV Robotics Expansion Hub and the REV Robotics color-range-light sensor. These changes were implemented to improve the reliability and resiliency of the FTC control system. Please note, however, that version 3.00 is considered "alpha" code. This code is being released so that the FIRST community will have an opportunity to test the new REV Expansion Hub electronics module when it becomes available in May. The developers do not recommend using this code for critical applications (i.e., competition use). *** Use this version of the software at YOUR OWN RISK!!! *** Changes include: Major rework of sensor-related infrastructure. Includes rewriting sensor classes to implement synchronous I2C communication. Fix to reset Autonomous timer back to 30 seconds. Implementation of specific motor profiles for approved 12V motors (includes Tetrix, AndyMark, Matrix and REV models). Modest improvements to enhance Wi-Fi P2P pairing. Fixes telemetry log addition race. Publishes all the sources (not just a select few). Includes Block programming improvements Addition of optimized Vuforia blocks. Auto scrollbar to projects and sounds pages. Fixed blocks paste bug. Blocks execute after while-opModeIsActive loop (to allow for cleanup before exiting op mode). Added gyro integratedZValue block. Fixes bug with projects page for Firefox browser. Added IsSpeaking block to AndroidTextToSpeech. Implements support for the REV Robotics Expansion Hub Implements support for integral REV IMU (physically installed on I2C bus 0, uses same Bosch BNO055 9 axis absolute orientation sensor as Adafruit 9DOF abs orientation sensor). - Implements support for REV color/range/light sensor. Provides support to update Expansion Hub firmware through FTC SDK. Detects REV firmware version and records in log file. Includes support for REV Control Hub (note that the REV Control Hub is not yet approved for FTC use). Implements FTC Blocks programming support for REV Expansion Hub and sensor hardware. Detects and alerts when I2C device disconnect. Version 2.62 (built on 17.01.07) Added null pointer check before calling modeToByte() in finishModeSwitchIfNecessary method for ModernRoboticsUsbDcMotorController class. Changes to enhance Modern Robotics USB protocol robustness. Version 2.61 (released on 16.12.19) Blocks Programming mode changes: Fix to correct issue when an exception was thrown because an OpticalDistanceSensor object appears twice in the hardware map (the second time as a LightSensor). Version 2.6 (released on 16.12.16) Fixes for Gyro class: Improve (decrease) sensor refresh latency. fix isCalibrating issues. Blocks Programming mode changes: Blocks now ignores a device in the configuration xml if the name is empty. Other devices work in configuration work fine. Version 2.5 (internal release on released on 16.12.13) Blocks Programming mode changes: Added blocks support for AdafruitBNO055IMU. Added Download Op Mode button to FtcBocks.html. Added support for copying blocks in one OpMode and pasting them in an other OpMode. The clipboard content is stored on the phone, so the programming mode server must be running. Modified Utilities section of the toolbox. In Programming Mode, display information about the active connections. Fixed paste location when workspace has been scrolled. Added blocks support for the android Accelerometer. Fixed issue where Blocks Upload Op Mode truncated name at first dot. Added blocks support for Android SoundPool. Added type safety to blocks for Acceleration. Added type safety to blocks for AdafruitBNO055IMU.Parameters. Added type safety to blocks for AnalogInput. Added type safety to blocks for AngularVelocity. Added type safety to blocks for Color. Added type safety to blocks for ColorSensor. Added type safety to blocks for CompassSensor. Added type safety to blocks for CRServo. Added type safety to blocks for DigitalChannel. Added type safety to blocks for ElapsedTime. Added type safety to blocks for Gamepad. Added type safety to blocks for GyroSensor. Added type safety to blocks for IrSeekerSensor. Added type safety to blocks for LED. Added type safety to blocks for LightSensor. Added type safety to blocks for LinearOpMode. Added type safety to blocks for MagneticFlux. Added type safety to blocks for MatrixF. Added type safety to blocks for MrI2cCompassSensor. Added type safety to blocks for MrI2cRangeSensor. Added type safety to blocks for OpticalDistanceSensor. Added type safety to blocks for Orientation. Added type safety to blocks for Position. Added type safety to blocks for Quaternion. Added type safety to blocks for Servo. Added type safety to blocks for ServoController. Added type safety to blocks for Telemetry. Added type safety to blocks for Temperature. Added type safety to blocks for TouchSensor. Added type safety to blocks for UltrasonicSensor. Added type safety to blocks for VectorF. Added type safety to blocks for Velocity. Added type safety to blocks for VoltageSensor. Added type safety to blocks for VuforiaLocalizer.Parameters. Added type safety to blocks for VuforiaTrackable. Added type safety to blocks for VuforiaTrackables. Added type safety to blocks for enums in AdafruitBNO055IMU.Parameters. Added type safety to blocks for AndroidAccelerometer, AndroidGyroscope, AndroidOrientation, and AndroidTextToSpeech. Version 2.4 (released on 16.11.13) Fix to avoid crashing for nonexistent resources. Blocks Programming mode changes: Added blocks to support OpenGLMatrix, MatrixF, and VectorF. Added blocks to support AngleUnit, AxesOrder, AxesReference, CameraDirection, CameraMonitorFeedback, DistanceUnit, and TempUnit. Added blocks to support Acceleration. Added blocks to support LinearOpMode.getRuntime. Added blocks to support MagneticFlux and Position. Fixed typos. Made blocks for ElapsedTime more consistent with other objects. Added blocks to support Quaternion, Velocity, Orientation, AngularVelocity. Added blocks to support VuforiaTrackables, VuforiaTrackable, VuforiaLocalizer, VuforiaTrackableDefaultListener. Fixed a few blocks. Added type checking to new blocks. Updated to latest blockly. Added default variable blocks to navigation and matrix blocks. Fixed toolbox entry for openGLMatrix_rotation_withAxesArgs. When user downloads Blocks-generated op mode, only the .blk file is downloaded. When user uploads Blocks-generated op mode (.blk file), Javascript code is auto generated. Added DbgLog support. Added logging when a blocks file is read/written. Fixed bug to properly render blocks even if missing devices from configuration file. Added support for additional characters (not just alphanumeric) for the block file names (for download and upload). Added support for OpMode flavor (“Autonomous” or “TeleOp”) and group. Changes to Samples to prevent tutorial issues. Incorporated suggested changes from public pull 216 (“Replace .. paths”). Remove Servo Glitches when robot stopped. if user hits “Cancels” when editing a configuration file, clears the unsaved changes and reverts to original unmodified configuration. Added log info to help diagnose why the Robot Controller app was terminated (for example, by watch dog function). Added ability to transfer log from the controller. Fixed inconsistency for AngularVelocity Limit unbounded growth of data for telemetry. If user does not call telemetry.update() for LinearOpMode in a timely manner, data added for telemetry might get lost if size limit is exceeded. Version 2.35 (released on 16.10.06) Blockly programming mode - Removed unnecesary idle() call from blocks for new project. Version 2.30 (released on 16.10.05) Blockly programming mode: Mechanism added to save Blockly op modes from Programming Mode Server onto local device To avoid clutter, blocks are displayed in categorized folders Added support for DigitalChannel Added support for ModernRoboticsI2cCompassSensor Added support for ModernRoboticsI2cRangeSensor Added support for VoltageSensor Added support for AnalogInput Added support for AnalogOutput Fix for CompassSensor setMode block Vuforia Fix deadlock / make camera data available while Vuforia is running. Update to Vuforia 6.0.117 (recommended by Vuforia and Google to close security loophole). Fix for autonomous 30 second timer bug (where timer was in effect, even though it appeared to have timed out). opModeIsActive changes to allow cleanup after op mode is stopped (with enforced 2 second safety timeout). Fix to avoid reading i2c twice. Updated sample Op Modes. Improved logging and fixed intermittent freezing. Added digital I/O sample. Cleaned up device names in sample op modes to be consistent with Pushbot guide. Fix to allow use of IrSeekerSensorV3. Version 2.20 (released on 16.09.08) Support for Modern Robotics Compass Sensor. Support for Modern Robotics Range Sensor. Revise device names for Pushbot templates to match the names used in Pushbot guide. Fixed bug so that IrSeekerSensorV3 device is accessible as IrSeekerSensor in hardwareMap. Modified computer vision code to require an individual Vuforia license (per legal requirement from PTC). Minor fixes. Blockly enhancements: Support for Voltage Sensor. Support for Analog Input. Support for Analog Output. Support for Light Sensor. Support for Servo Controller. Version 2.10 (released on 16.09.03) Support for Adafruit IMU. Improvements to ModernRoboticsI2cGyro class Block on reset of z axis. isCalibrating() returns true while gyro is calibration. Updated sample gyro program. Blockly enhancements support for android.graphics.Color. added support for ElapsedTime. improved look and legibility of blocks. support for compass sensor. support for ultrasonic sensor. support for IrSeeker. support for LED. support for color sensor. support for CRServo prompt user to configure robot before using programming mode. Provides ability to disable audio cues. various bug fixes and improvements. Version 2.00 (released on 16.08.19) This is the new release for the upcoming 2016-2017 FIRST Tech Challenge Season. Channel change is enabled in the FTC Robot Controller app for Moto G 2nd and 3rd Gen phones. Users can now use annotations to register/disable their Op Modes. Changes in the Android SDK, JDK and build tool requirements (minsdk=19, java 1.7, build tools 23.0.3). Standardized units in analog input. Cleaned up code for existing analog sensor classes. setChannelMode and getChannelMode were REMOVED from the DcMotorController class. This is important - we no longer set the motor modes through the motor controller. setMode and getMode were added to the DcMotor class. ContinuousRotationServo class has been added to the FTC SDK. Range.clip() method has been overloaded so it can support this operation for int, short and byte integers. Some changes have been made (new methods added) on how a user can access items from the hardware map. Users can now set the zero power behavior for a DC motor so that the motor will brake or float when power is zero. Prototype Blockly Programming Mode has been added to FTC Robot Controller. Users can place the Robot Controller into this mode, and then use a device (such as a laptop) that has a Javascript enabled browser to write Blockly-based Op Modes directly onto the Robot Controller. Users can now configure the robot remotely through the FTC Driver Station app. Android Studio project supports Android Studio 2.1.x and compile SDK Version 23 (Marshmallow). Vuforia Computer Vision SDK integrated into FTC SDK. Users can use sample vision targets to get localization information on a standard FTC field. Project structure has been reorganized so that there is now a TeamCode package that users can use to place their local/custom Op Modes into this package. Inspection function has been integrated into the FTC Robot Controller and Driver Station Apps (Thanks Team HazMat… 9277 & 10650!). Audio cues have been incorporated into FTC SDK. Swap mechanism added to FTC Robot Controller configuration activity. For example, if you have two motor controllers on a robot, and you misidentified them in your configuration file, you can use the Swap button to swap the devices within the configuration file (so you do not have to manually re-enter in the configuration info for the two devices). Fix mechanism added to all user to replace an electronic module easily. For example, suppose a servo controller dies on your robot. You replace the broken module with a new module, which has a different serial number from the original servo controller. You can use the Fix button to automatically reconfigure your configuration file to use the serial number of the new module. Improvements made to fix resiliency and responsiveness of the system. For LinearOpMode the user now must for a telemetry.update() to update the telemetry data on the driver station. This update() mechanism ensures that the driver station gets the updated data properly and at the same time. The Auto Configure function of the Robot Controller is now template based. If there is a commonly used robot configuration, a template can be created so that the Auto Configure mechanism can be used to quickly configure a robot of this type. The logic to detect a runaway op mode (both in the LinearOpMode and OpMode types) and to abort the run, then auto recover has been improved/implemented. Fix has been incorporated so that Logitech F310 gamepad mappings will be correct for Marshmallow users. Release 16.07.08 For the ftc_app project, the gradle files have been modified to support Android Studio 2.1.x. Release 16.03.30 For the MIT App Inventor, the design blocks have new icons that better represent the function of each design component. Some changes were made to the shutdown logic to ensure the robust shutdown of some of our USB services. A change was made to LinearOpMode so as to allow a given instance to be executed more than once, which is required for the App Inventor. Javadoc improved/updated. Release 16.03.09 Changes made to make the FTC SDK synchronous (significant change!) waitOneFullHardwareCycle() and waitForNextHardwareCycle() are no longer needed and have been deprecated. runOpMode() (for a LinearOpMode) is now decoupled from the system's hardware read/write thread. loop() (for an OpMode) is now decoupled from the system's hardware read/write thread. Methods are synchronous. For example, if you call setMode(DcMotorController.RunMode.RESET_ENCODERS) for a motor, the encoder is guaranteed to be reset when the method call is complete. For legacy module (NXT compatible), user no longer has to toggle between read and write modes when reading from or writing to a legacy device. Changes made to enhance reliability/robustness during ESD event. Changes made to make code thread safe. Debug keystore added so that user-generated robot controller APKs will all use the same signed key (to avoid conflicts if a team has multiple developer laptops for example). Firmware version information for Modern Robotics modules are now logged. Changes made to improve USB comm reliability and robustness. Added support for voltage indicator for legacy (NXT-compatible) motor controllers. Changes made to provide auto stop capabilities for op modes. A LinearOpMode class will stop when the statements in runOpMode() are complete. User does not have to push the stop button on the driver station. If an op mode is stopped by the driver station, but there is a run away/uninterruptible thread persisting, the app will log an error message then force itself to crash to stop the runaway thread. Driver Station UI modified to display lowest measured voltage below current voltage (12V battery). Driver Station UI modified to have color background for current voltage (green=good, yellow=caution, red=danger, extremely low voltage). javadoc improved (edits and additional classes). Added app build time to About activity for driver station and robot controller apps. Display local IP addresses on Driver Station About activity. Added I2cDeviceSynchImpl. Added I2cDeviceSync interface. Added seconds() and milliseconds() to ElapsedTime for clarity. Added getCallbackCount() to I2cDevice. Added missing clearI2cPortActionFlag. Added code to create log messages while waiting for LinearOpMode shutdown. Fix so Wifi Direct Config activity will no longer launch multiple times. Added the ability to specify an alternate i2c address in software for the Modern Robotics gyro. Release 16.02.09 Improved battery checker feature so that voltage values get refreshed regularly (every 250 msec) on Driver Station (DS) user interface. Improved software so that Robot Controller (RC) is much more resilient and “self-healing” to USB disconnects: If user attempts to start/restart RC with one or more module missing, it will display a warning but still start up. When running an op mode, if one or more modules gets disconnected, the RC & DS will display warnings,and robot will keep on working in spite of the missing module(s). If a disconnected module gets physically reconnected the RC will auto detect the module and the user will regain control of the recently connected module. Warning messages are more helpful (identifies the type of module that’s missing plus its USB serial number). Code changes to fix the null gamepad reference when users try to reference the gamepads in the init() portion of their op mode. NXT light sensor output is now properly scaled. Note that teams might have to readjust their light threshold values in their op modes. On DS user interface, gamepad icon for a driver will disappear if the matching gamepad is disconnected or if that gamepad gets designated as a different driver. Robot Protocol (ROBOCOL) version number info is displayed in About screen on RC and DS apps. Incorporated a display filter on pairing screen to filter out devices that don’t use the “-“ format. This filter can be turned off to show all WiFi Direct devices. Updated text in License file. Fixed formatting error in OpticalDistanceSensor.toString(). Fixed issue on with a blank (“”) device name that would disrupt WiFi Direct Pairing. Made a change so that the WiFi info and battery info can be displayed more quickly on the DS upon connecting to RC. Improved javadoc generation. Modified code to make it easier to support language localization in the future. Release 16.01.04 Updated compileSdkVersion for apps Prevent Wifi from entering power saving mode removed unused import from driver station Corrrected "Dead zone" joystick code. LED.getDeviceName and .getConnectionInfo() return null apps check for ROBOCOL_VERSION mismatch Fix for Telemetry also has off-by-one errors in its data string sizing / short size limitations error User telemetry output is sorted. added formatting variants to DbgLog and RobotLog APIs code modified to allow for a long list of op mode names. changes to improve thread safety of RobocolDatagramSocket Fix for "missing hardware leaves robot controller disconnected from driver station" error fix for "fast tapping of Init/Start causes problems" (toast is now only instantiated on UI thread). added some log statements for thread life cycle. moved gamepad reset logic inside of initActiveOpMode() for robustness changes made to mitigate risk of race conditions on public methods. changes to try and flag when WiFi Direct name contains non-printable characters. fix to correct race condition between .run() and .close() in ReadWriteRunnableStandard. updated FTDI driver made ReadWriteRunnableStanard interface public. fixed off-by-one errors in Command constructor moved specific hardware implmentations into their own package. moved specific gamepad implemnatations to the hardware library. changed LICENSE file to new BSD version. fixed race condition when shutting down Modern Robotics USB devices. methods in the ColorSensor classes have been synchronized. corrected isBusy() status to reflect end of motion. corrected "back" button keycode. the notSupported() method of the GyroSensor class was changed to protected (it should not be public). Release 15.11.04.001 Added Support for Modern Robotics Gyro. The GyroSensor class now supports the MR Gyro Sensor. Users can access heading data (about Z axis) Users can also access raw gyro data (X, Y, & Z axes). Example MRGyroTest.java op mode included. Improved error messages More descriptive error messages for exceptions in user code. Updated DcMotor API Enable read mode on new address in setI2cAddress Fix so that driver station app resets the gamepads when switching op modes. USB-related code changes to make USB comm more responsive and to display more explicit error messages. Fix so that USB will recover properly if the USB bus returns garbage data. Fix USB initializtion race condition. Better error reporting during FTDI open. More explicit messages during USB failures. Fixed bug so that USB device is closed if event loop teardown method was not called. Fixed timer UI issue Fixed duplicate name UI bug (Legacy Module configuration). Fixed race condition in EventLoopManager. Fix to keep references stable when updating gamepad. For legacy Matrix motor/servo controllers removed necessity of appending "Motor" and "Servo" to controller names. Updated HT color sensor driver to use constants from ModernRoboticsUsbLegacyModule class. Updated MR color sensor driver to use constants from ModernRoboticsUsbDeviceInterfaceModule class. Correctly handle I2C Address change in all color sensors Updated/cleaned up op modes. Updated comments in LinearI2cAddressChange.java example op mode. Replaced the calls to "setChannelMode" with "setMode" (to match the new of the DcMotor method). Removed K9AutoTime.java op mode. Added MRGyroTest.java op mode (demonstrates how to use MR Gyro Sensor). Added MRRGBExample.java op mode (demonstrates how to use MR Color Sensor). Added HTRGBExample.java op mode (demonstrates how to use HT legacy color sensor). Added MatrixControllerDemo.java (demonstrates how to use legacy Matrix controller). Updated javadoc documentation. Updated release .apk files for Robot Controller and Driver Station apps. Release 15.10.06.002 Added support for Legacy Matrix 9.6V motor/servo controller. Cleaned up build.gradle file. Minor UI and bug fixes for driver station and robot controller apps. Throws error if Ultrasonic sensor (NXT) is not configured for legacy module port 4 or 5. Release 15.08.03.001 New user interfaces for FTC Driver Station and FTC Robot Controller apps. An init() method is added to the OpMode class. For this release, init() is triggered right before the start() method. Eventually, the init() method will be triggered when the user presses an "INIT" button on driver station. The init() and loop() methods are now required (i.e., need to be overridden in the user's op mode). The start() and stop() methods are optional. A new LinearOpMode class is introduced. Teams can use the LinearOpMode mode to create a linear (not event driven) program model. Teams can use blocking statements like Thread.sleep() within a linear op mode. The API for the Legacy Module and Core Device Interface Module have been updated. Support for encoders with the Legacy Module is now working. The hardware loop has been updated for better performance.

With the growing popularity of BitCoin in the last couple of years, other blockchains have been in development for solving various problems that need distributed consensus. Ethereum blockchain is one example, that gives users to develop "smart contracts" that runs in the blockchain. This gives the ability to develop decentralized applications (or dApps). Users do not need to 'trust' anything or anybody. In addition to that, dApps are always available and will be guaranteed to be available in the future as well. Also, it is resistant to traditional attacks such as DDoS. This framework has given many developers to write a decentralized application without much effort, without needing distributed systems or cryptography knowledge. Many startups are actively developing applications for Ethereum such as Ethereum Name Service (ENS), Etheria or WeiFund. Unfortunately, because the technology being used is bleeding edge it is inevitable that attacks or hacks will target these apps for monetary reasons. Last year DAO suffered a severe attack because of its security flaws. Due to that attack, 3.6m ether was stolen from DAO's smart contract. Also, once you publish a smart contract in Ethereum it is not possible to modify or update it as a regular web application. Thus, even developers identify a critical bug in the contract it is not possible to push a bugfix in a straightforward way. Thus, in order to fill the gap of not having a proper 'smart contract' compatible monitoring service, we propose to build a web application that can monitor other smart contracts in Ethereum and give the capability to safeguard it's critical functions (Ether send and receive) and interact and visualize with smart contract functions in a much simpler way. Also depending smart contracts can using our base smart contracts to gain the advantage of having 'circuit-breaker' which will pause the activity if things go wrong in an unexpected way.

In IOT based monitoring project designed for keep on time track on the health status of the patient and updating to doctor at remote location anytime. With this effective device, health status of a critically ill patient can be constantly monitored. It can be used to keep track of health of aged people who frequently have heart or blood pressure issues. The IoT project developed here is built on Arduino UNO. It is interfaced with ESP8266 Wi-Fi modem to connect with an internet router and access the cloud server. The Arduino is interfaced with LM-35 temperature sensor to sense the body temperature and a pulse sensor to read pulse rate It continuously monitors the pulse rate and body temperature and updates them to an IoT platform. If any abnormalities are detected then system immediately sends notification to doctor. The IoT platform used in this project is ThingSpeak. Thingspeak has capabilities for Visualizing the collected data in the form of charts, Ability to create apps for collaborating with web services or social network and other APIs. The data from ThingSpeak to android application will send by HTTP request and HTTP response protocol. A threshold value is being set for pulse rate and body temperature. In android application there will be separate login credentials for patient and doctor. When the doctor will login, list of patients will be displayed along with two tags Patient Details and Health Status. In health status data from the Thingspeak will be fetched, doctor can check the medicine that the patient is consuming and can update is depending upon the health status. The patient can check the health status and medicine list and can also update details accordingly. Such a system consist of physiological data that stores, process and communicate through a local manner such as smart phones by using the system the health care professionals can monitor and advice their patient all the time.

# Liberty House Club **A Parallel Binance Chain to Enable Smart Contracts** _NOTE: This document is under development. Please check regularly for updates!_ ## Table of Contents - [Motivation](#motivation) - [Design Principles](#design-principles) - [Consensus and Validator Quorum](#consensus-and-validator-quorum) * [Proof of Staked Authority](#proof-of-staked-authority) * [Validator Quorum](#validator-quorum) * [Security and Finality](#security-and-finality) * [Reward](#reward) - [Token Economy](#token-economy) * [Native Token](#native-token) * [Other Tokens](#other-tokens) - [Cross-Chain Transfer and Communication](#cross-chain-transfer-and-communication) * [Cross-Chain Transfer](#cross-chain-transfer) * [BC to BSC Architecture](#bc-to-bsc-architecture) * [BSC to BC Architecture](#bsc-to-bc-architecture) * [Timeout and Error Handling](#timeout-and-error-handling) * [Cross-Chain User Experience](#cross-chain-user-experience) * [Cross-Chain Contract Event](#cross-chain-contract-event) - [Staking and Governance](#staking-and-governance) * [Staking on BC](#staking-on-bc) * [Rewarding](#rewarding) * [Slashing](#slashing) - [Relayers](#relayers) * [BSC Relayers](#bsc-relayers) * [Oracle Relayers](#oracle-relayers) - [Outlook](#outlook) # Motivation After its mainnet community [launch](https://www.binance.com/en/blog/327334696200323072/Binance-DEX-Launches-on-Binance-Chain-Invites-Further-Community-Development) in April 2019, [Binance Chain](https://www.binance.org) has exhibited its high speed and large throughput design. Binance Chain’s primary focus, its native [decentralized application](https://en.wikipedia.org/wiki/Decentralized_application) (“dApp”) [Binance DEX](https://www.binance.org/trade), has demonstrated its low-latency matching with large capacity headroom by handling millions of trading volume in a short time. Flexibility and usability are often in an inverse relationship with performance. The concentration on providing a convenient digital asset issuing and trading venue also brings limitations. Binance Chain's most requested feature is the programmable extendibility, or simply the [Smart Contract](https://en.wikipedia.org/wiki/Smart_contract) and Virtual Machine functions. Digital asset issuers and owners struggle to add new decentralized features for their assets or introduce any sort of community governance and activities. Despite this high demand for adding the Smart Contract feature onto Binance Chain, it is a hard decision to make. The execution of a Smart Contract may slow down the exchange function and add non-deterministic factors to trading. If that compromise could be tolerated, it might be a straightforward idea to introduce a new Virtual Machine specification based on [Tendermint](https://tendermint.com/core/), based on the current underlying consensus protocol and major [RPC](https://docs.binance.org/api-reference/node-rpc.html) implementation of Binance Chain. But all these will increase the learning requirements for all existing dApp communities, and will not be very welcomed. We propose a parallel blockchain of the current Binance Chain to retain the high performance of the native DEX blockchain and to support a friendly Smart Contract function at the same time. # Design Principles After the creation of the parallel blockchain into the Binance Chain ecosystem, two blockchains will run side by side to provide different services. The new parallel chain will be called “**Binance Smart Chain**” (short as “**BSC**” for the below sections), while the existing mainnet remains named “**Binance Chain**” (short as “**BC**” for the below sections). Here are the design principles of **BSC**: 1. **Standalone Blockchain**: technically, BSC is a standalone blockchain, instead of a layer-2 solution. Most BSC fundamental technical and business functions should be self-contained so that it can run well even if the BC stopped for a short period. 2. **Ethereum Compatibility**: The first practical and widely-used Smart Contract platform is Ethereum. To take advantage of the relatively mature applications and community, BSC chooses to be compatible with the existing Ethereum mainnet. This means most of the **dApps**, ecosystem components, and toolings will work with BSC and require zero or minimum changes; BSC node will require similar (or a bit higher) hardware specification and skills to run and operate. The implementation should leave room for BSC to catch up with further Ethereum upgrades. 3. **Staking Involved Consensus and Governance**: Staking-based consensus is more environmentally friendly and leaves more flexible option to the community governance. Expectedly, this consensus should enable better network performance over [proof-of-work](https://en.wikipedia.org/wiki/Proof_of_work) blockchain system, i.e., faster blocking time and higher transaction capacity. 4. **Native Cross-Chain Communication**: both BC and BSC will be implemented with native support for cross-chain communication among the two blockchains. The communication protocol should be bi-directional, decentralized, and trustless. It will concentrate on moving digital assets between BC and BSC, i.e., [BEP2](https://github.com/binance-chain/BEPs/blob/master/BEP2.md) tokens, and eventually, other BEP tokens introduced later. The protocol should care for the minimum of other items stored in the state of the blockchains, with only a few exceptions. # Consensus and Validator Quorum Based on the above design principles, the consensus protocol of BSC is to fulfill the following goals: 1. Blocking time should be shorter than Ethereum network, e.g. 5 seconds or even shorter. 2. It requires limited time to confirm the finality of transactions, e.g. around 1-min level or shorter. 3. There is no inflation of native token: BNB, the block reward is collected from transaction fees, and it will be paid in BNB. 4. It is compatible with Ethereum system as much as possible. 5. It allows modern [proof-of-stake](https://en.wikipedia.org/wiki/Proof_of_stake) blockchain network governance. ## Proof of Staked Authority Although Proof-of-Work (PoW) has been recognized as a practical mechanism to implement a decentralized network, it is not friendly to the environment and also requires a large size of participants to maintain the security. Ethereum and some other blockchain networks, such as [MATIC Bor](https://github.com/maticnetwork/bor), [TOMOChain](https://tomochain.com/), [GoChain](https://gochain.io/), [xDAI](https://xdai.io/), do use [Proof-of-Authority(PoA)](https://en.wikipedia.org/wiki/Proof_of_authority) or its variants in different scenarios, including both testnet and mainnet. PoA provides some defense to 51% attack, with improved efficiency and tolerance to certain levels of Byzantine players (malicious or hacked). It serves as an easy choice to pick as the fundamentals. Meanwhile, the PoA protocol is most criticized for being not as decentralized as PoW, as the validators, i.e. the nodes that take turns to produce blocks, have all the authorities and are prone to corruption and security attacks. Other blockchains, such as EOS and Lisk both, introduce different types of [Delegated Proof of Stake (DPoS)](https://en.bitcoinwiki.org/wiki/DPoS) to allow the token holders to vote and elect the validator set. It increases the decentralization and favors community governance. BSC here proposes to combine DPoS and PoA for consensus, so that: 1. Blocks are produced by a limited set of validators 2. Validators take turns to produce blocks in a PoA manner, similar to [Ethereum’s Clique](https://eips.ethereum.org/EIPS/eip-225) consensus design 3. Validator set are elected in and out based on a staking based governance ## Validator Quorum In the genesis stage, a few trusted nodes will run as the initial Validator Set. After the blocking starts, anyone can compete to join as candidates to elect as a validator. The staking status decides the top 21 most staked nodes to be the next validator set, and such an election will repeat every 24 hours. **BNB** is the token used to stake for BSC. In order to remain as compatible as Ethereum and upgradeable to future consensus protocols to be developed, BSC chooses to rely on the **BC** for staking management (Please refer to the below “[Staking and Governance](#staking-and-governance)” section). There is a **dedicated staking module for BSC on BC**. It will accept BSC staking from BNB holders and calculate the highest staked node set. Upon every UTC midnight, BC will issue a verifiable `ValidatorSetUpdate` cross-chain message to notify BSC to update its validator set. While producing further blocks, the existing BSC validators check whether there is a `ValidatorSetUpdate` message relayed onto BSC periodically. If there is, they will update the validator set after an **epoch period**, i.e. a predefined number of blocking time. For example, if BSC produces a block every 5 seconds, and the epoch period is 240 blocks, then the current validator set will check and update the validator set for the next epoch in 1200 seconds (20 minutes). ## Security and Finality Given there are more than ½\*N+1 validators are honest, PoA based networks usually work securely and properly. However, there are still cases where certain amount Byzantine validators may still manage to attack the network, e.g. through the “[Clone Attack](https://arxiv.org/pdf/1902.10244.pdf)”. To secure as much as BC, BSC users are encouraged to wait until receiving blocks sealed by more than ⅔\*N+1 different validators. In that way, the BSC can be trusted at a similar security level to BC and can tolerate less than ⅓\*N Byzantine validators. With 21 validators, if the block time is 5 seconds, the ⅔\*N+1 different validator seals will need a time period of (⅔\*21+1)*5 = 75 seconds. Any critical applications for BSC may have to wait for ⅔\*N+1 to ensure a relatively secure finality. However, besides such arrangement, BSC does introduce **Slashing** logic to penalize Byzantine validators for **double signing** or **inavailability**, which will be covered in the “Staking and Governance” section later. This Slashing logic will expose the malicious validators in a very short time and make the “Clone Attack” very hard or extremely non-beneficial to execute. With this enhancement, ½\*N+1 or even fewer blocks are enough as confirmation for most transactions. ## Reward All the BSC validators in the current validator set will be rewarded with transaction **fees in BNB**. As BNB is not an inflationary token, there will be no mining rewards as what Bitcoin and Ethereum network generate, and the gas fee is the major reward for validators. As BNB is also utility tokens with other use cases, delegators and validators will still enjoy other benefits of holding BNB. The reward for validators is the fees collected from transactions in each block. Validators can decide how much to give back to the delegators who stake their BNB to them, in order to attract more staking. Every validator will take turns to produce the blocks in the same probability (if they stick to 100% liveness), thus, in the long run, all the stable validators may get a similar size of the reward. Meanwhile, the stakes on each validator may be different, so this brings a counter-intuitive situation that more users trust and delegate to one validator, they potentially get less reward. So rational delegators will tend to delegate to the one with fewer stakes as long as the validator is still trustful (insecure validator may bring slashable risk). In the end, the stakes on all the validators will have less variation. This will actually prevent the stake concentration and “winner wins forever” problem seen on some other networks. Some parts of the gas fee will also be rewarded to relayers for Cross-Chain communication. Please refer to the “[Relayers](#relayers)” section below. # Token Economy BC and BSC share the same token universe for BNB and BEP2 tokens. This defines: 1. The same token can circulate on both networks, and flow between them bi-directionally via a cross-chain communication mechanism. 2. The total circulation of the same token should be managed across the two networks, i.e. the total effective supply of a token should be the sum of the token’s total effective supply on both BSC and BC. 3. The tokens can be initially created on BSC in a similar format as ERC20 token standard, or on BC as a BEP2, then created on the other. There are native ways on both networks to link the two and secure the total supply of the token. ## Native Token BNB will run on BSC in the same way as ETH runs on Ethereum so that it remains as “native token” for both BSC and BC. This means, in addition to BNB is used to pay most of the fees on Binance Chain and Binance DEX, BNB will be also used to: 1. pay “fees“ to deploy smart contracts on BSC 2. stake on selected BSC validators, and get corresponding rewards 3. perform cross-chain operations, such as transfer token assets across BC and BSC ### Seed Fund Certain amounts of BNB will be burnt on BC and minted on BSC during its genesis stage. This amount is called “Seed Fund” to circulate on BSC after the first block, which will be dispatched to the initial BC-to-BSC Relayer(described in later sections) and initial validator set introduced at genesis. These BNBs are used to pay transaction fees in the early stage to transfer more BNB from BC onto BSC via the cross-chain mechanism. The BNB cross-chain transfer is discussed in a later section, but for BC to BSC transfer, it is generally to lock BNB on BC from the source address of the transfer to a system-controlled address and unlock the corresponding amount from special contract to the target address of the transfer on BSC, or reversely, when transferring from BSC to BC, it is to lock BNB from the source address on BSC into a special contract and release locked amount on BC from the system address to the target address. The logic is related to native code on BC and a series of smart contracts on BSC. ## Other Tokens BC supports BEP2 tokens and upcoming [BEP8 tokens](https://github.com/binance-chain/BEPs/pull/69), which are native assets transferrable and tradable (if listed) via fast transactions and sub-second finality. Meanwhile, as BSC is Ethereum compatible, it is natural to support ERC20 tokens on BSC, which here is called “**BEP2E**” (with the real name to be introduced by the future BEPs,it potentially covers BEP8 as well). BEP2E may be “Enhanced” by adding a few more methods to expose more information, such as token denomination, decimal precision definition and the owner address who can decide the Token Binding across the chains. BSC and BC work together to ensure that one token can circulate in both formats with confirmed total supply and be used in different use cases. ### Token Binding BEP2 tokens will be extended to host a new attribute to associate the token with a BSC BEP2E token contract, called “**Binder**”, and this process of association is called “**Token Binding**”. Token Binding can happen at any time after BEP2 and BEP2E are ready. The token owners of either BEP2 or BEP2E don’t need to bother about the Binding, until before they really want to use the tokens on different scenarios. Issuers can either create BEP2 first or BEP2E first, and they can be bound at a later time. Of course, it is encouraged for all the issuers of BEP2 and BEP2E to set the Binding up early after the issuance. A typical procedure to bind the BEP2 and BEP2E will be like the below: 1. Ensure both the BEP2 token and the BEP2E token both exist on each blockchain, with the same total supply. BEP2E should have 3 more methods than typical ERC20 token standard: * symbol(): get token symbol * decimals(): get the number of the token decimal digits * owner(): get **BEP2E contract owner’s address.** This value should be initialized in the BEP2E contract constructor so that the further binding action can verify whether the action is from the BEP2E owner. 2. Decide the initial circulation on both blockchains. Suppose the total supply is *S*, and the expected initial circulating supply on BC is *K*, then the owner should lock S-K tokens to a system controlled address on BC. 3. Equivalently, *K* tokens is locked in the special contract on BSC, which handles major binding functions and is named as **TokenHub**. The issuer of the BEP2E token should lock the *K* amount of that token into TokenHub, resulting in *S-K* tokens to circulate on BSC. Thus the total circulation across 2 blockchains remains as *S*. 4. The issuer of BEP2 token sends the bind transaction on BC. Once the transaction is executed successfully after proper verification: * It transfers *S-K* tokens to a system-controlled address on BC. * A cross-chain bind request package will be created, waiting for Relayers to relay. 5. BSC Relayers will relay the cross-chain bind request package into **TokenHub** on BSC, and the corresponding request and information will be stored into the contract. 6. The contract owner and only the owner can run a special method of TokenHub contract, `ApproveBind`, to verify the binding request to mark it as a success. It will confirm: * the token has not been bound; * the binding is for the proper symbol, with proper total supply and decimal information; * the proper lock are done on both networks; 10. Once the `ApproveBind` method has succeeded, TokenHub will mark the two tokens are bounded and share the same circulation on BSC, and the status will be propagated back to BC. After this final confirmation, the BEP2E contract address and decimals will be written onto the BEP2 token as a new attribute on BC, and the tokens can be transferred across the two blockchains bidirectionally. If the ApproveBind fails, the failure event will also be propagated back to BC to release the locked tokens, and the above steps can be re-tried later. # Cross-Chain Transfer and Communication Cross-chain communication is the key foundation to allow the community to take advantage of the dual chain structure: * users are free to create any tokenization, financial products, and digital assets on BSC or BC as they wish * the items on BSC can be manually and programmingly traded and circulated in a stable, high throughput, lighting fast and friendly environment of BC * users can operate these in one UI and tooling ecosystem. ## Cross-Chain Transfer The cross-chain transfer is the key communication between the two blockchains. Essentially the logic is: 1. the `transfer-out` blockchain will lock the amount from source owner addresses into a system controlled address/contracts; 2. the `transfer-in` blockchain will unlock the amount from the system controlled address/contracts and send it to target addresses. The cross-chain transfer package message should allow the BSC Relayers and BC **Oracle Relayers** to verify: 1. Enough amount of token assets are removed from the source address and locked into a system controlled addresses/contracts on the source blockchain. And this can be confirmed on the target blockchain. 2. Proper amounts of token assets are released from a system controlled addresses/contracts and allocated into target addresses on the target blockchain. If this fails, it can be confirmed on source blockchain, so that the locked token can be released back (may deduct fees). 3. The sum of the total circulation of the token assets across the 2 blockchains are not changed after this transfer action completes, no matter if the transfer succeeds or not.  The architecture of cross-chain communication is as in the above diagram. To accommodate the 2 heteroid systems, communication handling is different in each direction. ## BC to BSC Architecture BC is a Tendermint-based, instant finality blockchain. Validators with at least ⅔\*N+1 of the total voting power will co-sign each block on the chain. So that it is practical to verify the block transactions and even the state value via **Block Header** and **Merkle Proof** verification. This has been researched and implemented as “**Light-Client Protocol**”, which are intensively discussed in [the Ethereum](https://github.com/ethereum/wiki/wiki/Light-client-protocol) community, studied and implemented for [Cosmos inter-chain communication](https://github.com/cosmos/ics/blob/a4173c91560567bdb7cc9abee8e61256fc3725e9/spec/ics-007-tendermint-client/README.md). BC-to-BSC communication will be verified in an “**on-chain light client**” implemented via BSC **Smart Contracts** (some of them may be **“pre-compiled”**). After some transactions and state change happen on BC, if a transaction is defined to trigger cross-chain communication,the Cross-chain “**package**” message will be created and **BSC Relayers** will pass and submit them onto BSC as data into the "build-in system contracts". The build-in system contracts will verify the package and execute the transactions if it passes the verification. The verification will be guaranteed with the below design: 1. BC blocking status will be synced to the light client contracts on BSC from time to time, via block header and pre-commits, for the below information: * block and app hash of BC that are signed by validators * current validatorset, and validator set update 2. the key-value from the blockchain state will be verified based on the Merkle Proof and information from above #1. After confirming the key-value is accurate and trustful, the build-in system contracts will execute the actions corresponding to the cross-chain packages. Some examples of such packages that can be created for BC-to-BSC are: 1. Bind: bind the BEP2 tokens and BEP2E 2. Transfer: transfer tokens after binding, this means the circulation will decrease (be locked) from BC and appear in the target address balance on BSC 3. Error Handling: to handle any timeout/failure event for BSC-to-BC communication 4. Validatorset update of BSC To ensure no duplication, proper message sequence and timely timeout, there is a “Channel” concept introduced on BC to manage any types of the communication. For relayers, please also refer to the below “Relayers” section. ## BSC to BC Architecture BSC uses Proof of Staked Authority consensus protocol, which has a chance to fork and requires confirmation of more blocks. One block only has the signature of one validator, so that it is not easy to rely on one block to verify data from BSC. To take full advantage of validator quorum of BC, an idea similar to many [Bridge ](https://github.com/poanetwork/poa-bridge)or Oracle blockchains is adopted: 1. The cross-chain communication requests from BSC will be submitted and executed onto BSC as transactions. The execution of the transanction wil emit `Events`, and such events can be observed and packaged in certain “**Oracle**” onto BC. Instead of Block Headers, Hash and Merkle Proof, this type of “Oracle” package directly contains the cross-chain information for actions, such as sender, receiver and amount for transfer. 2. To ensure the security of the Oracle, the validators of BC will form anothe quorum of “**Oracle Relayers**”. Each validator of the BC should run a **dedicated process** as the Oracle Relayer. These Oracle Relayers will submit and vote for the cross-chain communication package, like Oracle, onto BC, using the same validator keys. Any package signed by more than ⅔\*N+1 Oracle Relayers’ voting power is as secure as any block signed by ⅔\*N+1 of the same quorum of validators’ voting power. By using the same validator quorum, it saves the light client code on BC and continuous block updates onto BC. Such Oracles also have Oracle IDs and types, to ensure sequencing and proper error handling. ## Timeout and Error Handling There are scenarios that the cross-chain communication fails. For example, the relayed package cannot be executed on BSC due to some coding bug in the contracts. **Timeout and error handling logics are** used in such scenarios. For the recognizable user and system errors or any expected exceptions, the two networks should heal themselves. For example, when BC to BSC transfer fails, BSC will issue a failure event and Oracle Relayers will execute a refund on BC; when BSC to BC transfer fails, BC will issue a refund package for Relayer to relay in order to unlock the fund. However, unexpected error or exception may still happen on any step of the cross-chain communication. In such a case, the Relayers and Oracle Relayers will discover that the corresponding cross-chain channel is stuck in a particular sequence. After a Timeout period, the Relayers and Oracle Relayers can request a “SkipSequence” transaction, the stuck sequence will be marked as “Unexecutable”. A corresponding alerts will be raised, and the community has to discuss how to handle this scenario, e.g. payback via the sponsor of the validators, or event clear the fund during next network upgrade. ## Cross-Chain User Experience Ideally, users expect to use two parallel chains in the same way as they use one single chain. It requires more aggregated transaction types to be added onto the cross-chain communication to enable this, which will add great complexity, tight coupling, and maintenance burden. Here BC and BSC only implement the basic operations to enable the value flow in the initial launch and leave most of the user experience work to client side UI, such as wallets. E.g. a great wallet may allow users to sell a token directly from BSC onto BC’s DEX order book, in a secure way. ## Cross-Chain Contract Event Cross-Chain Contract Event (CCCE) is designed to allow a smart contract to trigger cross-chain transactions, directly through the contract code. This becomes possible based on: 1. Standard system contracts can be provided to serve operations callable by general smart contracts; 2. Standard events can be emitted by the standard contracts; 3. Oracle Relayers can capture the standard events, and trigger the corresponding cross-chain operations; 4. Dedicated, code-managed address (account) can be created on BC and accessed by the contracts on the BSC, here it is named as **“Contract Address on BC” (CAoB)**. Several standard operations are implemented: 1. BSC to BC transfer: this is implemented in the same way as normal BSC to BC transfer, by only triggered via standard contract. The fund can be transferred to any addresses on BC, including the corresponding CAoB of the transfer originating contract. 2. Transfer on BC: this is implemented as a special cross-chain transfer, while the real transfer is from **CAoB** to any other address (even another CAoB). 3. BC to BSC transfer: this is implemented as two-pass cross-chain communication. The first is triggered by the BSC contract and propagated onto BC, and then in the second pass, BC will start a normal BC to BSC cross-chain transfer, from **CAoB** to contract address on BSC. A special note should be paid on that the BSC contract only increases balance upon any transfer coming in on the second pass, and the error handling in the second pass is the same as the normal BC to BSC transfer. 4. IOC (Immediate-Or-Cancel) Trade Out: the primary goal of transferring assets to BC is to trade. This event will instruct to trade a certain amount of an asset in CAoB into another asset as much as possible and transfer out all the results, i.e. the left the source and the traded target tokens of the trade, back to BSC. BC will handle such relayed events by sending an “Immediate-Or-Cancel”, i.e. IOC order onto the trading pairs, once the next matching finishes, the result will be relayed back to BSC, which can be in either one or two assets. 5. Auction Trade Out: Such event will instruct BC to send an auction order to trade a certain amount of an asset in **CAoB** into another asset as much as possible and transfer out all the results back to BSC at the end of the auction. Auction function is upcoming on BC. There are some details for the Trade Out: 1. both can have a limit price (absolute or relative) for the trade; 2. the end result will be written as cross-chain packages to relay back to BSC; 3. cross-chain communication fees may be charged from the asset transferred back to BSC; 4. BSC contract maintains a mirror of the balance and outstanding orders on CAoB. No matter what error happens during the Trade Out, the final status will be propagated back to the originating contract and clear its internal state. With the above features, it simply adds the cross-chain transfer and exchange functions with high liquidity onto all the smart contracts on BSC. It will greatly add the application scenarios on Smart Contract and dApps, and make 1 chain +1 chain > 2 chains. # Staking and Governance Proof of Staked Authority brings in decentralization and community involvement. Its core logic can be summarized as the below. You may see similar ideas from other networks, especially Cosmos and EOS. 1. Token holders, including the validators, can put their tokens “**bonded**” into the stake. Token holders can **delegate** their tokens onto any validator or validator candidate, to expect it can become an actual validator, and later they can choose a different validator or candidate to **re-delegate** their tokens¹. 2. All validator candidates will be ranked by the number of bonded tokens on them, and the top ones will become the real validators. 3. Validators can share (part of) their blocking reward with their delegators. 4. Validators can suffer from “**Slashing**”, a punishment for their bad behaviors, such as double sign and/or instability. 5. There is an “**unbonding period**” for validators and delegators so that the system makes sure the tokens remain bonded when bad behaviors are caught, the responsible will get slashed during this period. ## Staking on BC Ideally, such staking and reward logic should be built into the blockchain, and automatically executed as the blocking happens. Cosmos Hub, who shares the same Tendermint consensus and libraries with Binance Chain, works in this way. BC has been preparing to enable staking logic since the design days. On the other side, as BSC wants to remain compatible with Ethereum as much as possible, it is a great challenge and efforts to implement such logic on it. This is especially true when Ethereum itself may move into a different Proof of Stake consensus protocol in a short (or longer) time. In order to keep the compatibility and reuse the good foundation of BC, the staking logic of BSC is implemented on BC: 1. The staking token is BNB, as it is a native token on both blockchains anyway 2. The staking, i.e. token bond and delegation actions and records for BSC, happens on BC. 3. The BSC validator set is determined by its staking and delegation logic, via a staking module built on BC for BSC, and propagated every day UTC 00:00 from BC to BSC via Cross-Chain communication. 4. The reward distribution happens on BC around every day UTC 00:00. ## Rewarding Both the validator update and reward distribution happen every day around UTC 00:00. This is to save the cost of frequent staking updates and block reward distribution. This cost can be significant, as the blocking reward is collected on BSC and distributed on BC to BSC validators and delegators. (Please note BC blocking fees will remain rewarding to BC validators only.) A deliberate delay is introduced here to make sure the distribution is fair: 1. The blocking reward will not be sent to validator right away, instead, they will be distributed and accumulated on a contract; 2. Upon receiving the validator set update into BSC, it will trigger a few cross-chain transfers to transfer the reward to custody addresses on the corresponding validators. The custody addresses are owned by the system so that the reward cannot be spent until the promised distribution to delegators happens. 3. In order to make the synchronization simpler and allocate time to accommodate slashing, the reward for N day will be only distributed in N+2 days. After the delegators get the reward, the left will be transferred to validators’ own reward addresses. ## Slashing Slashing is part of the on-chain governance, to ensure the malicious or negative behaviors are punished. BSC slash can be submitted by anyone. The transaction submission requires **slash evidence** and cost fees but also brings a larger reward when it is successful. So far there are two slashable cases. ### Double Sign It is quite a serious error and very likely deliberate offense when a validator signs more than one block with the same height and parent block. The reference protocol implementation should already have logic to prevent this, so only the malicious code can trigger this. When Double Sign happens, the validator should be removed from the Validator **Set** right away. Anyone can submit a slash request on BC with the evidence of Double Sign of BSC, which should contain the 2 block headers with the same height and parent block, sealed by the offending validator. Upon receiving the evidence, if the BC verifies it to be valid: 1. The validator will be removed from validator set by an instance BSC validator set update Cross-Chain update; 2. A predefined amount of BNB would be slashed from the **self-delegated** BNB of the validator; Both validator and its delegators will not receive the staking rewards. 3. Part of the slashed BNB will allocate to the submitter’s address, which is a reward and larger than the cost of submitting slash request transaction 4. The rest of the slashed BNB will allocate to the other validators’ custody addresses, and distributed to all delegators in the same way as blocking reward. ### Inavailability The liveness of BSC relies on everyone in the Proof of Staked Authority validator set can produce blocks timely when it is their turn. Validators can miss their turn due to any reason, especially problems in their hardware, software, configuration or network. This instability of the operation will hurt the performance and introduce more indeterministic into the system. There can be an internal smart contract responsible for recording the missed blocking metrics of each validator. Once the metrics are above the predefined threshold, the blocking reward for validator will not be relayed to BC for distribution but shared with other better validators. In such a way, the poorly-operating validator should be gradually voted out of the validator set as their delegators will receive less or none reward. If the metrics remain above another higher level of threshold, the validator will be dropped from the rotation, and this will be propagated back to BC, then a predefined amount of BNB would be slashed from the **self-delegated** BNB of the validator. Both validators and delegators will not receive their staking rewards. ### Governance Parameters There are many system parameters to control the behavior of the BSC, e.g. slash amount, cross-chain transfer fees. All these parameters will be determined by BSC Validator Set together through a proposal-vote process based on their staking. Such the process will be carried on BC, and the new parameter values will be picked up by corresponding system contracts via a cross-chain communication. # Relayers Relayers are responsible to submit Cross-Chain Communication Packages between the two blockchains. Due to the heterogeneous parallel chain structure, two different types of Relayers are created. ## BSC Relayers Relayers for BC to BSC communication referred to as “**BSC Relayers**”, or just simply “Relayers”. Relayer is a standalone process that can be run by anyone, and anywhere, except that Relayers must register themselves onto BSC and deposit a certain refundable amount of BNB. Only relaying requests from the registered Relayers will be accepted by BSC. The package they relay will be verified by the on-chain light client on BSC. The successful relay needs to pass enough verification and costs gas fees on BSC, and thus there should be incentive reward to encourage the community to run Relayers. ### Incentives There are two major communication types: 1. Users triggered Operations, such as `token bind` or `cross chain transfer`. Users must pay additional fee to as relayer reward. The reward will be shared with the relayers who sync the referenced blockchain headers. Besides, the reward won't be paid the relayers' accounts directly. A reward distribution mechanism will be brought in to avoid monopolization. 2. System Synchronization, such as delivering `refund package`(caused by failures of most oracle relayers), special blockchain header synchronization(header contains BC validatorset update), BSC staking package. System reward contract will pay reward to relayers' accounts directly. If some Relayers have faster networks and better hardware, they can monopolize all the package relaying and leave no reward to others. Thus fewer participants will join for relaying, which encourages centralization and harms the efficiency and security of the network. Ideally, due to the decentralization and dynamic re-election of BSC validators, one Relayer can hardly be always the first to relay every message. But in order to avoid the monopolization further, the rewarding economy is also specially designed to minimize such chance: 1. The reward for Relayers will be only distributed in batches, and one batch will cover a number of successful relayed packages. 2. The reward a Relayer can get from a batch distribution is not linearly in proportion to their number of successful relayed packages. Instead, except the first a few relays, the more a Relayer relays during a batch period, the less reward it will collect. ## Oracle Relayers Relayers for BSC to BC communication are using the “Oracle” model, and so-called “**Oracle Relayers**”. Each of the validators must, and only the ones of the validator set, run Oracle Relayers. Each Oracle Relayer watches the blockchain state change. Once it catches Cross-Chain Communication Packages, it will submit to vote for the requests. After Oracle Relayers from ⅔ of the voting power of BC validators vote for the changes, the cross-chain actions will be performed. Oracle Replayers should wait for enough blocks to confirm the finality on BSC before submitting and voting for the cross-chain communication packages onto BC. The cross-chain fees will be distributed to BC validators together with the normal BC blocking rewards. Such oracle type relaying depends on all the validators to support. As all the votes for the cross-chain communication packages are recorded on the blockchain, it is not hard to have a metric system to assess the performance of the Oracle Relayers. The poorest performer may have their rewards clawed back via another Slashing logic introduced in the future. # Outlook It is hard to conclude for Binance Chain, as it has never stopped evolving. The dual-chain strategy is to open the gate for users to take advantage of the fast transferring and trading on one side, and flexible and extendable programming on the other side, but it will be one stop along the development of Binance Chain. Here below are the topics to look into so as to facilitate the community better for more usability and extensibility: 1. Add different digital asset model for different business use cases 2. Enable more data feed, especially DEX market data, to be communicated from Binance DEX to BSC 3. Provide interface and compatibility to integrate with Ethereum, including its further upgrade, and other blockchain 4. Improve client side experience to manage wallets and use blockchain more conveniently ------ [1]: BNB business practitioners may provide other benefits for BNB delegators, as they do now for long term BNB holders.

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What is C++? C++ is a general-purpose, object-oriented programming language. It was created by Bjarne Stroustrup at Bell Labs circa 1980. C++ is very similar to C (invented by Dennis Ritchie in the early 1970s). C++ is so compatible with C that it will probably compile over 99% of C programs without changing a line of source code. Though C++ is a lot of well-structured and safer language than C as it OOPs based. Some computer languages are written for a specific purpose. Like, Java was initially devised to control toasters and some other electronics. C was developed for programming OS. Pascal was conceptualized to teach proper programming techniques. But C++ is a general-purpose language. It well deserves the widely acknowledged nickname "Swiss Pocket Knife of Languages." C++ is a cross-platform language that can be used to create high-performance applications. C++ was developed by Bjarne Stroustrup, as an extension to the C language. C++ gives programmers a high level of control over system resources and memory. The language was updated 3 major times in 2011, 2014, and 2017 to C++11, C++14, and C++17. About C++ Programming Multi-paradigm Language - C++ supports at least seven different styles of programming. Developers can choose any of the styles. General Purpose Language - You can use C++ to develop games, desktop apps, operating systems, and so on. Speed - Like C programming, the performance of optimized C++ code is exceptional. Object-oriented - C++ allows you to divide complex problems into smaller sets by using objects. Why Learn C++? C++ is used to develop games, desktop apps, operating systems, browsers, and so on because of its performance. After learning C++, it will be much easier to learn other programming languages like Java, Python, etc. C++ helps you to understand the internal architecture of a computer, how computer stores and retrieves information. How to learn C++? C++ tutorial from Programiz - We provide step by step C++ tutorials, examples, and references. Get started with C++. Official C++ documentation - Might be hard to follow and understand for beginners. Visit official C++ documentation. Write a lot of C++ programming code- The only way you can learn programming is by writing a lot of code. Read C++ code- Join Github's open-source projects and read other people's code. C++ best programming language? The answer depends on perspective and requirements. Some tasks can be done in C++, though not very quickly. For example, designing GUI screens for applications. Other languages like Visual Basic, Python have GUI design elements built into them. Therefore, they are better suited for GUI type of task. Some of the scripting languages that provide extra programmability to applications. Such as MS Word and even photoshop tend to be variants of Basic, not C++. C++ is still used widely, and the most famous software have their backbone in C++. This tutorial will help you learn C++ basic and the advanced concepts. Who uses C++? Some of today's most visible used systems have their critical parts written in C++. Examples are Amadeus (airline ticketing) Bloomberg (financial formation), Amazon (Web commerce), Google (Web search) Facebook (social media) Many programming languages depend on C++'s performance and reliability in their implementation. Examples include: Java Virtual Machines JavaScript interpreters (e.g., Google's V8) Browsers (e.g., Internet Explorer, Mozilla's Firefox, Apple's Safari, and Google's Chrome) Application and Web frameworks (e.g., Microsoft's .NET Web services framework). Applications that involve local and wide area networks, user interaction, numeric, graphics, and database access highly depend on C++ language. Why Use C++ C++ is one of the world's most popular programming languages. C++ can be found in today's operating systems, Graphical User Interfaces, and embedded systems. C++ is an object-oriented programming language which gives a clear structure to programs and allows code to be reused, lowering development costs. C++ is portable and can be used to develop applications that can be adapted to multiple platforms. C++ is fun and easy to learn! As C++ is close to C# and Java, it makes it easy for programmers to switch to C++ or vice versa Definition - What does C++ Programming Language mean? C++ is an object oriented computer language created by notable computer scientist Bjorne Stroustrop as part of the evolution of the C family of languages. Some call C++ “C with classes” because it introduces object oriented programming principles, including the use of defined classes, to the C programming language framework. C++ is pronounced "see-plus-plus." C++ Variables Variables are the backbone of any programming language. A variable is merely a way to store some information for later use. We can retrieve this value or data by referring to a "word" that will describe this information. Once declared and defined they may be used many times within the scope in which they were declared. C++ Control Structures When a program runs, the code is read by the compiler line by line (from top to bottom, and for the most part left to right). This is known as "code flow." When the code is being read from top to bottom, it may encounter a point where it needs to make a decision. Based on the decision, the program may jump to a different part of the code. It may even make the compiler re-run a specific piece again, or just skip a bunch of code. You could think of this process like if you were to choose from different courses from Guru99. You decide, click a link and skip a few pages. In the same way, a computer program has a set of strict rules to decide the flow of program execution. C++ Syntax The syntax is a layout of words, expression, and symbols. Well, it's because an email address has its well-defined syntax. You need some combination of letters, numbers, potentially with underscores (_) or periods (.) in between, followed by an at the rate (@) symbol, followed by some website domain (company.com). So, syntax in a programming language is much the same. They are some well-defined set of rules that allow you to create some piece of well-functioning software. But, if you don't abide by the rules of a programming language or syntax, you'll get errors. C++ Tools In the real world, a tool is something (usually a physical object) that helps you to get a certain job done promptly. Well, this holds true with the programming world too. A tool in programming is some piece of software which when used with the code allows you to program faster. There are probably tens of thousands, if not millions of different tools across all the programming languages. Most crucial tool, considered by many, is an IDE, an Integrated Development Environment. An IDE is a software which will make your coding life so much easier. IDEs ensure that your files and folders are organized and give you a nice and clean way to view them. Types of C++ Errors Another way to look at C++ in a practical sense is to start enumerating different kinds of errors that occur as the written code makes its way to final execution. First, there are syntax errors where the code is actually written in an illegible way. This can be a misuse of punctuation, or the misspelling of a function command or anything else that compromises the integrity of the syntax as it is written. Another fundamental type of error is a compiler error that simply tells the programmer the compiler was not able to do its work effectively. As a compiler language, C++ relies on the compiler to make the source code into machine readable code and optimize it in various ways. A third type of error happens after the program has been successfully compiled. Runtime errors are not uncommon in C++ executables. What they represent is some lack of designated resource or non-working command in the executable program. In other words, the syntax is right, and the program was compiled successfully, but as the program is doing its work, it encounters a problem, whether that has to do with interdependencies, operating system requirements or anything else in the general environment in which the program is trying to work. Over time, C++ has remained a very useful language not only in computer programming itself, but in teaching new programmers about how object oriented programming works.

SmartRev is a web app that is designed to scrape and classify critical reviews on pet food from Chewy's website into three categories of health, quality and service, and surface the most helpful review in each category.

Angular-Directive-Project Directives range from very basic to extremely complex. This project will build up to some somewhat difficult directives. Keep in mind that the format we're learning for directives is the same format used to build some extremely complex things in angular. Using directives often and well is one way to show you're a talented developer. Starting Out We've included only a few things for you to begin with. index.html, app.js, styles.css. At this point the best way to get more comfortable with angular is to initialize an app without relying heavily on boilerplate code (reusable code that starts out your projects for you). You'll notice that in the index.html we've included the angular-route CDN. Yes, we'll be using angular's router here. Put an ng-view into your index.html. In your app.js set up a config and set up our first route for when a user is at the '/home' url. If you're having trouble remembering how to set up the router go look at how you set up the router on the previous project. One way these projects will be beneficial to you is allowing you to look back at something *you** did and seeing how you got that something to work.* You may also want add an otherwise that defaults to /home. Create a controller and a template file for this route in your app folder. Don't forget to include the controller as a script in your index.html Check that everything is hooked up correctly. Try adding a div with some text in your home template just to make sure it's showing up. Once you've got that going you're ready to start on some directives. Now let's make our directive. We'll start with a simple one that we can use to display information passed to it. Step 1. Start your directive Woot. When you're initializing your directive just remember that it works very similarly to how you start up a controller or a service. It can also be very helpful to think of your directive as a route. Create your directive. You'll use the directive method on your angular module. It takes two arguments, the name string and the callback function, which will return the object that represents your directive. When naming your directive give it a name with two words; dirDisplay would be nice, but anything works. Just remember it's best practice to give a directive a camel case name so that it's clear in your html what it is. Also we're going to need a template html for our directive. We could do it inline, but let's make another file instead. Just name it something that makes sense for the name of your directive and put it in the same directory as your directive file. For your template just make a <div> and inside a <h1> tag that says User. Now in your home route html add in your directive. It will look like this if you named it dirDisplay: <dir-display></dir-display> Start up your app and go to the home route. Check and make sure you see User where your directive was placed. If you're not seeing it at this point it could mean a few things. Here's some more common issues. You didn't link your directive in your index as a script. Your name for your directive doesn't match the name in your html. Remember camel case becomes snake case so myDirective becomes <my-directive></my-directive>. You're file path to your html template is wrong. You have to think of file paths in angular as relative to the index. Here's some code to see just for this part, and just for the directive's js file. var app = angular.module('directivePractice'); app.directive('dirDisplay', function(){ return { templateUrl: 'app/directives/dirDisplay.html' }; }); What we're returning is the directive object. You won't see anymore code in this tutorial so it's important you get things working right and refer back to what you've already done to advance from now on. Step 2. Advancing directives Your directive should be loaded up now, but it's not really doing much. Let's make it better. In your home controller. Make a variable on your $scope called user. Set it's value to { name: "Geoff McMammy", age: 43, email: "geofdude@gmail.com" } Now inside your directive's html specifically inside the <h3> tags display our new user's name. Then inside maybe some <h4> tags display his email and age. This is going to work exactly the same as if it was just inside your home controller. Reload the page and make sure it works. This is still very cosmetic and really not all that useful. It needs functionality. Add into your directive's object the link property. The link property's value is a function definition that takes (generally) three parameters. scope, element, and attributes. Unlike in other places with angular injection these parameter names don't carry meaning. The first parameter will always represent your $scope for that directive, the second will always be the element that wraps your whole directive, and the third will always be an object containing all the properties and values of the attributes on your directive in the dom. Try the following to get a feel for all three. Add two attributes to your directive in your html. Like this - <dir-display test="myTest" my-check="checkItOut"></dir-display> Now in the link property you've added console.log the three parameters in the function. You'll see an object for scope that should look identical to the $scope of your html function. For element you'll see an object the represents the DOM wrapper for your directive. For attributes you'll see an object that will look like this: { test: "myTest", myCheck: "checkItOut" } An important thing to notice is how it has again converted snake case to camel case for you. my-check became myCheck. Don't forget this. You'll run into this issue one day. It counts for both attributes and directive names. To feel some of what the link function could do let's try this. Add a ng-show to both the email and age wrappers. This should be familiar to you. Now inside your link function add a click event listener to your element property. It's going to look just like jQuery. element.on('click', function(){ }) Inside the click listener's callback add a toggle for the ng-show property you passed in. Along with a console.log to make sure things are connecting when you click. Try it out. Don't call for a mentor when it doesn't work. Let's talk about that first. You should see the console.log firing, but why isn't it toggling. This is going to be a common problem when working with the link function and event listeners. What we have here is an angular digest problem. The value is changing on the scope object, but the change isn't being reflected by our DOM. That's because angular isn't aware of the change yet. Anytime we cause an event to happen using something like jQuery or even angular's jQLite we need to let angular know that we've made a change. Add this line of code in place of your console.log, scope.$apply(). Now try it out. It should be working now, so if you're still having issues it's time to debug. What we've done is forced angular to run it's digest cycle. This is where angular checks the scope object for changes and then applies those to the DOM. This is another good lesson to learn for later. You'll most likely hit this when making changes to your element using event listeners. Step 3. Directive's re-usability. Now our directive has some extremely basic functionality. One of a directive's greatest advantages though is its ability to be placed anywhere and still be functional. Let's say instead we had a list of users instead of just one. Change the $scope property in your home controller to be users and give it this array as its value: [ { name: "Geoff McMammy", age: 43, email: "geofdude@gmail.com", city: "Provo" }, { name: "Frederick Deeder", age: 26, email: "fredeed@gmail.com", city: "Austin" }, { name: "Spencer Rentz", age: 35, email: "spencerrentz@gmail.com", city: "Sacramento" }, { name: "Geddup Ngo", age: 43, email: "geddupngo@gmail.com", city: "Orlando" }, { name: "Donst Opbie Leevin", age: 67, email: "gernee@gmail.com", city: "Phoenix" } ] Now in your home HTML add a ng-repeat to the directive call. Tell it to repeat for each user in users. Reload your page. It's working! But why? How does each directive instance know what information to display? In the link function console.log the scope parameter. Make sure it's outside of your click listener. You'll see five print outs in your console. Open up any one of them and look to the bottom. Open up the user property. It's exactly what we would want! But again why would that be the case? Don't get too caught up in this next bit if it's too hard to understand, but the ng-repeat is essentially making new tiny scope objects for each individual user in our users array. Now each of our directives is still getting a user property on the scope object just like the directive wanted in the beginning. Woot. Step 4. Ramp it up with Isolate Scope. Directives can do so much more. So let's make that happen. That means we should make.... a new directive!!! This directive's purpose will be to display a selected User and the weather in his/her/its location. Link it up just like the last one. Create a js file for our directive and name it dirWeather. Make an html file named dirWeather.html. Link it up in your index.html and add the template to your new directive object. In your directive's template give it an <h3> tag that says Weather just so we can know it's working. Above your ng-repeat on dirDisplay add your new dirWeather directive. If it's not working check the instructions above as to some common reasons why before asking a mentor for help. If you're seeing the Weather text on your page then we're ready to try out the dreaded Isolate Scope. The isolate scope object is one of the stranger API's in angular. I'm sorry but it is. Just refer to this for now. scope: { string: '@', link: '=', func: '&' } The properties on the scope object represent the attributes on the directive in the html. Our example scope object here would look something like this in the html. <example-directive string="a string" link="user" func="updateUser()"></example-directive> The hard part here is the @, =, and &. They each have very important and distinct meanings. @ says take in my attribute value as a string. = says take in my attribute value as a two-way bound variable from the parent scope. & says take in my attribute value as a reference to a function on the parent scope. It's also critical to point out that once you add a scope object you have no isolated your directive's scope. Meaning, aside from the values passed in through attributes, this directive has no connection to the $scope of its parent. That being said let's isolate our directive's scope. :worried: Add the scope property to your dirWeather. Give it the value of an object with a property of currentUser whose value is '='. Remember in your html this will look like current-user. This is the third time I've said so don't expect it again. This means that whatever comes into the currentUser attribute is going to be a value of the parent's scope object. For now test this out by passing in users[0]. Find a way to show that users information inside your dirWeather's html. Remember inside your directive now the user is represented by currentUser. Step 5. &? &!? The '=' value on your scope object has created a two-way binding between users[0] and currentUser. Now let's try out the '&'. On your home controller add a function called getWeather. It takes one parameter called city. This function will make a call to a service so we'll need to create that. Make a weather service. Name it something cool and creative like weatherService. Inside the weather service make a function called getWeather that also takes one parameter, city. Make an $http get to this url - 'http://api.openweathermap.org/data/2.5/weather?q=' After the q= add on the city parameter. If you want you can test this out in postman. See what kind of data you get back. If it's the weather of that city then... you win! Use $q to return a promise that only resolves with the data you want. Temperature (preferably not in Kelvin) and the weather description. Use console.log on the data coming from the $http request to get to what you want. You'll need to add both on an object that you resolve your new promise with. On your home controller have it return the result of invoking the get getWeather function on the service. You should be returning a promise. Now in your home route's HTML pass in the getWeather function to the dirWeather directive through an attribute called weather-call. Add the attribute to your isolate scope object. That was a lot of linking, but let's walk through it. Your controller has a function linked to the service, which is in turn linked to your directive. So if you run the weatherCall function in your directive it will go through your controller to your service and then back. Now things get a little bit tricky. Angular's way of passing along arguments through a directive to your controller are tricky, but once you understand how to do it, it's not hard. I'm going to give an example here of how it works. <my-directive pass-func="callFunc(data)"></my-directive> Here's how it would look in your HTML. But where's the data supposed to be coming from? It seems that you'd rather be able to pass in data from your directive. Well you still can, you just have to essentially tell angular what do use as an argument to replace data when it calls that function in your controller. The actualy function call inside the directive will look like this. $scope.passFunc({data: wantedData}) So what you'll do is pass in an object where the property name is what the argument is named in the HTML where you call the directive. That might sound confusing, but just look at the two code blocks above for a pattern. Note that pass-func becomes $scope.passFunc and data is being replaced with wantedData with the {data: wantedData} object. In our directive we want to replace city in the attribute call, for something else inside the directive. You'll follow the same pattern as above. For now let's get things set up for that function call. Add to the dirWeather directive object a property called controller. It's value will be a function. Yes, this is a controller specifically for your one directive. It works the same as any other controller, except you don't give it a name. It's $scope object will only be accessible within an instance of your directive. Don't forget to inject $scope in the function. Inside your controller function run the weatherCall function with the city property from the currentUser on your $scope. Here's where you need to make sure you've passed in a city argument in the attribute function call, and then replace that with your currentUser's city using an object with a city property. The function call should return a promise, so call .then afterward and add the data onto your $scope to display both the weather and temperature of the currentUser's city. The properties can be named whatever makes sense to you. You may also want to find a way to get rid of all the decimal places on your temperature. Now you should have everything hooked up so it shows Geoff's data and the weather data for Provo. But is that good enough? Step 6. Ramping up our ramp up. Now let's change this so it shows the weather data for whichever user we select. We're going to need to use '&' again. Make a function on the home controller that takes in a parameter and sets a property on the $scope to be that parameter. Maybe you see where this is going. We want to get this function into our dirDisplay controller. But in order to do that we need to isolate dirDisplay's scope. This also means we need to pass in each individual user through the scope object as well. To make it easier on ourselves, let's pass the current user from our ng-repeat into our directive through a user attribute. This way we can leave our two-way bindings as they are. Also pass our new function that sets our current user from our home controller into our directive through a setUser attribute. You'll need to add an argument in there again. Go with user. Your scope object in dirDisplay should have two properties. setUser with the value of '&' and user with the value of '='. As before we're going to need to do some tricky stuff to get our argument back to our controller. Call the setUser function inside our click event listener and pass in an object the sets our user argument to be the user on our directive's scope object. If you've forgotten this part go back up and take a look at how you did it before or the example in this README. Whatever user you click on now should show up in the dirWeather directive as the current user. But we're missing one thing, we want to be able to see the weather for that user too. We'll have to do one more thing that will seem a little bit tricky at first, but it's good to learn if you don't know it already since it's actually used quite frequently. We need to step up a change listener on our currentUser in the dirWeather directive. We'll use angular's $watch functionality. $watch is a method on your $scope that will watch for changes in a variable you give it. It works in two ways. $scope.$watch('property', function(value){ console.log("When $scope.property changes its new value is: ", value) }); And $scope.$watch(function(){ return myVar }, function(value){ console.log("When myVar changes its new value is: ", value); }); Remove the immediate function call that we have in there now. Maybe just comment it out for now because we'll use it in a bit. Now call the $watch method on your scope and have it watch currentUser. Either way of using $watch is fine. Have its callback run the $scope.weatherCall function just like you had it before. One thing to note is that $scope.$watch will always run once to begin with. Since that's what we want here it's great, but just be aware of that. If you've reached this point congratulate yourself. You've messed with some serious stuff today, namely directives. There are still a lot of things about directives that we can't possibly cover in a single project. If you like what we've done so far then you're in a good place to keep going. A developer who understands directives well can build a really clean looking code base. Just look at your home.html. It could have just two lines in it. If you're feeling good move on now to Step 7. Step 7. Finishing touches Try to work out these problems on your own. There should be a way to let the user know that the weather data is loading. Something that appears while our $http request is retrieving our data. The $http request shouldn't fire on both opening and closing a user's information. A color change for the currently active user would be nicer than showing that user's info inside the dirWeather modal. Or at least less redundant. Whatever else you want. We still haven't explored transclusion and ng-transclude so give that a try if you're feeling adventurous. Just know that it's a way for deciding where to put the HTML child elements of a directive. It's cool stuff that can involve some criss-crossing of scopes.

Service Criticality App

This repository contains a basic app shell which uses the following concepts: critical resource rendering, service worker to cache static and dynamic assets, App Shell architecture, Progressive Web App

Look around and you will find people with smart devices that track their every move, calculate their intake and gives them trends on this data. Primitively, Caregivers and hospitals were using telemetry to remotely gather data for improving patient care. The primary aim of preventive healthcare was to deliver personalized care, improve patient care while reducing costs. However, Internet of Medical Things (IoMT) is driving the future of healthcare for better outcomes, improving efficiency and making healthcare more affordable as caretakers are increasingly resorting to more self- care due to increased awareness. To get there, healthcare providers must make use of technology in a more systematic way. The Scope of IoT is getting bigger and better in: Preventive healthcare: by use of wearables. Patient tracking: in monitoring patient movement and health analysis. Geriatric care: in tracking Senior citizens which is a large market for IoT, medical devices. Real-time location: in tracking medical devices, people and asset movement. Gartner believes that 30% of smart wearables will be unobtrusive to the eye by 2017. it is predicted that the revenue from smart wearable devices will generate $22.9 billion by 2020. Experts from P&S Market research expect that the healthcare Internet of Things industry will grow at a compound annual growth rate (CAGR) of 37.6 percent between 2015 and 2020. The rising need for advanced healthcare combined with the requirements of Affordable Care Act (ACA), technology in the industry is expected to grow through 2020 Wearables for preventive health analysis Imagine a wearable used for preventive health analysis. The term wearable in health parlance should not be restricted to just fitness tracking devices worn in the wrist that are used to monitor personal health. By and far, this term should go beyond tracking of physical activities; it could be used as a communication device or it could even be a device that interacts with other devices like an Apple watch, track patients’ body conditions, sleep patterns or any other critical information which may require immediate care. It could be a device in the body, on the body or near the body like a medical app that helps track personal health; Some of the industry medical apps that are already disrupting the healthcare market are Philips’ Medication Dispensing Service Airfinder Boiron Medicine Finder App Future Path Medical’s Urosense Digital Hospitals making headway Healthcare is increasingly leveraging modern technology and digital hospitals are making headway such as the Humber River Hospital in Toronto Canada and the Medical Center at Mission Bay San Francisco. Innovative approaches towards engaging robots in the radiology and other departments are also disrupting the way healthcare is delivered. Deakin University Australia, in partnership with Telstra Australia, has developed haptics-enabled robots that can perform ultrasound diagnostics remotely. This means the patient need not be in the same place as the sonographer conducting the ultrasound. IoMT for improved healthcare There were 165,000 mobile healthcare apps as of November 2015 and the mobile app marketplace is expected to grow 15 times faster, according to a survey. Another survey shows users expect digital healthcare services to be able to communicate with doctors via their smartphones, monitor health and collaborate with care givers with ease. IoMT is slowly and steadily reducing human intervention and dependency to provide early diagnosis and contributing to improved healthcare in accordance with the Patient Protection and Affordable Care Act which focus on certified EHR (Electronic Health Record) to enhance efficiency and quality of patient care. Conclusion: With the cost of Hardware coming down, software enabling devices to talk to multiple devices across platforms is going to redefine the way people take care of their health. The biggest change is going to be in Preventive Healthcare, making it the biggest gamechanger.

What is C++? C++ is a general-purpose, object-oriented programming language. It was created by Bjarne Stroustrup at Bell Labs circa 1980. C++ is very similar to C (invented by Dennis Ritchie in the early 1970s). C++ is so compatible with C that it will probably compile over 99% of C programs without changing a line of source code. Though C++ is a lot of well-structured and safer language than C as it OOPs based. Some computer languages are written for a specific purpose. Like, Java was initially devised to control toasters and some other electronics. C was developed for programming OS. Pascal was conceptualized to teach proper programming techniques. But C++ is a general-purpose language. It well deserves the widely acknowledged nickname "Swiss Pocket Knife of Languages." C++ is a cross-platform language that can be used to create high-performance applications. C++ was developed by Bjarne Stroustrup, as an extension to the C language. C++ gives programmers a high level of control over system resources and memory. The language was updated 3 major times in 2011, 2014, and 2017 to C++11, C++14, and C++17. About C++ Programming Multi-paradigm Language - C++ supports at least seven different styles of programming. Developers can choose any of the styles. General Purpose Language - You can use C++ to develop games, desktop apps, operating systems, and so on. Speed - Like C programming, the performance of optimized C++ code is exceptional. Object-oriented - C++ allows you to divide complex problems into smaller sets by using objects. Why Learn C++? C++ is used to develop games, desktop apps, operating systems, browsers, and so on because of its performance. After learning C++, it will be much easier to learn other programming languages like Java, Python, etc. C++ helps you to understand the internal architecture of a computer, how computer stores and retrieves information. How to learn C++? C++ tutorial from Programiz - We provide step by step C++ tutorials, examples, and references. Get started with C++. Official C++ documentation - Might be hard to follow and understand for beginners. Visit official C++ documentation. Write a lot of C++ programming code- The only way you can learn programming is by writing a lot of code. Read C++ code- Join Github's open-source projects and read other people's code. C++ best programming language? T he answer depends on perspective and requirements. Some tasks can be done in C++, though not very quickly. For example, designing GUI screens for applications. Other languages like Visual Basic, Python have GUI design elements built into them. Therefore, they are better suited for GUI type of task. Some of the scripting languages that provide extra programmability to applications. Such as MS Word and even photoshop tend to be variants of Basic, not C++. C++ is still used widely, and the most famous software have their backbone in C++. This tutorial will help you learn C++ basic and the advanced concepts. Who uses C++? Some of today's most visible used systems have their critical parts written in C++. Examples are Amadeus (airline ticketing) Bloomberg (financial formation), Amazon (Web commerce), Google (Web search) Facebook (social media) Many programming languages depend on C++'s performance and reliability in their implementation. Examples include: Java Virtual Machines JavaScript interpreters (e.g., Google's V8) Browsers (e.g., Internet Explorer, Mozilla's Firefox, Apple's Safari, and Google's Chrome) Application and Web frameworks (e.g., Microsoft's .NET Web services framework). Applications that involve local and wide area networks, user interaction, numeric, graphics, and database access highly depend on C++ language. Why Use C++ C++ is one of the world's most popular programming languages. C++ can be found in today's operating systems, Graphical User Interfaces, and embedded systems. C++ is an object-oriented programming language which gives a clear structure to programs and allows code to be reused, lowering development costs. C++ is portable and can be used to develop applications that can be adapted to multiple platforms. C++ is fun and easy to learn! As C++ is close to C# and Java, it makes it easy for programmers to switch to C++ or vice versa Definition - What does C++ Programming Language mean? C++ is an object oriented computer language created by notable computer scientist Bjorne Stroustrop as part of the evolution of the C family of languages. Some call C++ “C with classes” because it introduces object oriented programming principles, including the use of defined classes, to the C programming language framework. C++ is pronounced "see-plus-plus." C++ Variables Variables are the backbone of any programming language. A variable is merely a way to store some information for later use. We can retrieve this value or data by referring to a "word" that will describe this information. Once declared and defined they may be used many times within the scope in which they were declared. C++ Control Structures When a program runs, the code is read by the compiler line by line (from top to bottom, and for the most part left to right). This is known as "code flow." When the code is being read from top to bottom, it may encounter a point where it needs to make a decision. Based on the decision, the program may jump to a different part of the code. It may even make the compiler re-run a specific piece again, or just skip a bunch of code. You could think of this process like if you were to choose from different courses from Guru99. You decide, click a link and skip a few pages. In the same way, a computer program has a set of strict rules to decide the flow of program execution. C++ Syntax The syntax is a layout of words, expression, and symbols. Well, it's because an email address has its well-defined syntax. You need some combination of letters, numbers, potentially with underscores (_) or periods (.) in between, followed by an at the rate (@) symbol, followed by some website domain (company.com). So, syntax in a programming language is much the same. They are some well-defined set of rules that allow you to create some piece of well-functioning software. But, if you don't abide by the rules of a programming language or syntax, you'll get errors. C++ Tools In the real world, a tool is something (usually a physical object) that helps you to get a certain job done promptly. Well, this holds true with the programming world too. A tool in programming is some piece of software which when used with the code allows you to program faster. There are probably tens of thousands, if not millions of different tools across all the programming languages. Most crucial tool, considered by many, is an IDE, an Integrated Development Environment. An IDE is a software which will make your coding life so much easier. IDEs ensure that your files and folders are organized and give you a nice and clean way to view them. Types of C++ Errors Another way to look at C++ in a practical sense is to start enumerating different kinds of errors that occur as the written code makes its way to final execution. First, there are syntax errors where the code is actually written in an illegible way. This can be a misuse of punctuation, or the misspelling of a function command or anything else that compromises the integrity of the syntax as it is written. Another fundamental type of error is a compiler error that simply tells the programmer the compiler was not able to do its work effectively. As a compiler language, C++ relies on the compiler to make the source code into machine readable code and optimize it in various ways. A third type of error happens after the program has been successfully compiled. Runtime errors are not uncommon in C++ executables. What they represent is some lack of designated resource or non-working command in the executable program. In other words, the syntax is right, and the program was compiled successfully, but as the program is doing its work, it encounters a problem, whether that has to do with interdependencies, operating system requirements or anything else in the general environment in which the program is trying to work. Over time, C++ has remained a very useful language not only in computer programming itself, but in teaching new programmers about how object oriented programming works.

An Android SOS application built with Jetpack Compose that allows users to save emergency contacts and quickly send SOS messages along with their real-time location via SMS in critical situations. The app ensures user safety by integrating location services and SMS permissions seamlessly, providing a reliable one-tap emergency alert solution.

Quick Start to Field Service Lightning With Field Service Lightning, you can streamline operations across the full service chain on a single platform, resulting in a more integrated client experience. You can redefine the connected customer experience by giving your agents, dispatchers, and mobile staff the tools they need to provide a strong customer experience anytime, anywhere, and on any mobile device with Field Service Lightning. How does Field Service Lightning Benefit the Workforce Field Service Lightning is a single platform that links your entire workforce, allowing you to provide your clients with faster, smarter, and more personalized on-site service. It not only allows your employees to stay on top of things, but it also allows customers to easily book their own appointments through a customer community. From the bottom of the food chain to the top, Field Service Lightning delivers vital tools for all team members. Mobile Employees Use the all-in-one mobile app to get all of the information they need to execute each job properly. They can see the parts they'll need, the steps they'll need to complete each assignment, and even get directions to the location. Support Agents Have access to appointment scheduling, which allows them to see detailed case feeds, real-time milestone monitoring, and worker skills and knowledge. Dispatchers From the dispatcher dashboard, you can view and manage all scheduled tasks, coordinate resources, and use Map View and Field Service Management Tools for real-time monitoring of all field employees. Managers Capable of managing field resource management, as well as critical customer and employee KPIs, in order to ensure that operations are as effective and productive as possible in the salesforce service cloud. Capture Data and Focus on Success The appointment scheduling procedure is automated with salesforce field service management. As a result, field service requests are resolved faster and the appropriate service resource is allocated to the project, resulting in increased customer satisfaction. The productivity of service resources is boosted by having all of the tools needed on mobile devices to handle work orders and service reports rapidly. Everything is stored in one location, from installations and repairs to preventative maintenance, in order to retain that important 360-degree client view. Consider several salesforce field service lightning pricing before integration. Outcomes Create work orders quickly from any case. Create and manage field service work orders, as well as access Knowledge articles and track SLA compliance with Milestones. Work orders are linked to Accounts, Contacts, Assets, Cases, Entitlements, and other Salesforce Field Service Lightning objects, allowing you to pull data from several sources. Optimize scheduling and assign jobs sensibly. From the Service Console or a Customer Community, you may book truth-based service appointments right away with Field Service Lightning Implementation. To boost employee productivity, jobs are automatically assigned to the proper resource based on time, talents, location, and any business rules with intelligent scheduling. Companies have incorporated sophisticated scheduling and tracking of employees, equipment, and trucks to guarantee the proper parts are accessible for the job with economical field service salesforce pricing. Increase your first-time repair rate by leveraging the power of AI. Field Service Lightning Consulting analysts may utilize image recognition with AI Vision to quickly identify assets and parts in photos. To avoid confusion and extra trips back to the office, make sure the correct product part is repaired or replaced. You can automatically prescribe the right set up steps for technicians based on an image's classification, so they can provide faster, smarter Salesforce Field Service.

This is the main application on which the idea originated, through this app customers could use the provided services with a simple and fast registration process at first time using this app, that could be helpful in many critical situations when a customer has any issues related to his car.

What is C++? C++ is a general-purpose, object-oriented programming language. It was created by Bjarne Stroustrup at Bell Labs circa 1980. C++ is very similar to C (invented by Dennis Ritchie in the early 1970s). C++ is so compatible with C that it will probably compile over 99% of C programs without changing a line of source code. Though C++ is a lot of well-structured and safer language than C as it OOPs based. Some computer languages are written for a specific purpose. Like, Java was initially devised to control toasters and some other electronics. C was developed for programming OS. Pascal was conceptualized to teach proper programming techniques. But C++ is a general-purpose language. It well deserves the widely acknowledged nickname "Swiss Pocket Knife of Languages." C++ is a cross-platform language that can be used to create high-performance applications. C++ was developed by Bjarne Stroustrup, as an extension to the C language. C++ gives programmers a high level of control over system resources and memory. The language was updated 3 major times in 2011, 2014, and 2017 to C++11, C++14, and C++17. About C++ Programming Multi-paradigm Language - C++ supports at least seven different styles of programming. Developers can choose any of the styles. General Purpose Language - You can use C++ to develop games, desktop apps, operating systems, and so on. Speed - Like C programming, the performance of optimized C++ code is exceptional. Object-oriented - C++ allows you to divide complex problems into smaller sets by using objects. Why Learn C++? C++ is used to develop games, desktop apps, operating systems, browsers, and so on because of its performance. After learning C++, it will be much easier to learn other programming languages like Java, Python, etc. C++ helps you to understand the internal architecture of a computer, how computer stores and retrieves information. How to learn C++? C++ tutorial from Programiz - We provide step by step C++ tutorials, examples, and references. Get started with C++. Official C++ documentation - Might be hard to follow and understand for beginners. Visit official C++ documentation. Write a lot of C++ programming code- The only way you can learn programming is by writing a lot of code. Read C++ code- Join Github's open-source projects and read other people's code. C++ best programming language? The answer depends on perspective and requirements. Some tasks can be done in C++, though not very quickly. For example, designing GUI screens for applications. Other languages like Visual Basic, Python have GUI design elements built into them. Therefore, they are better suited for GUI type of task. Some of the scripting languages that provide extra programmability to applications. Such as MS Word and even photoshop tend to be variants of Basic, not C++. C++ is still used widely, and the most famous software have their backbone in C++. This tutorial will help you learn C++ basic and the advanced concepts. Who uses C++? Some of today's most visible used systems have their critical parts written in C++. Examples are Amadeus (airline ticketing) Bloomberg (financial formation), Amazon (Web commerce), Google (Web search) Facebook (social media) Many programming languages depend on C++'s performance and reliability in their implementation. Examples include: Java Virtual Machines JavaScript interpreters (e.g., Google's V8) Browsers (e.g., Internet Explorer, Mozilla's Firefox, Apple's Safari, and Google's Chrome) Application and Web frameworks (e.g., Microsoft's .NET Web services framework). Applications that involve local and wide area networks, user interaction, numeric, graphics, and database access highly depend on C++ language. Why Use C++ C++ is one of the world's most popular programming languages. C++ can be found in today's operating systems, Graphical User Interfaces, and embedded systems. C++ is an object-oriented programming language which gives a clear structure to programs and allows code to be reused, lowering development costs. C++ is portable and can be used to develop applications that can be adapted to multiple platforms. C++ is fun and easy to learn! As C++ is close to C# and Java, it makes it easy for programmers to switch to C++ or vice versa Definition - What does C++ Programming Language mean? C++ is an object oriented computer language created by notable computer scientist Bjorne Stroustrop as part of the evolution of the C family of languages. Some call C++ “C with classes” because it introduces object oriented programming principles, including the use of defined classes, to the C programming language framework. C++ is pronounced "see-plus-plus." C++ Variables Variables are the backbone of any programming language. A variable is merely a way to store some information for later use. We can retrieve this value or data by referring to a "word" that will describe this information. Once declared and defined they may be used many times within the scope in which they were declared. C++ Control Structures When a program runs, the code is read by the compiler line by line (from top to bottom, and for the most part left to right). This is known as "code flow." When the code is being read from top to bottom, it may encounter a point where it needs to make a decision. Based on the decision, the program may jump to a different part of the code. It may even make the compiler re-run a specific piece again, or just skip a bunch of code. You could think of this process like if you were to choose from different courses from Guru99. You decide, click a link and skip a few pages. In the same way, a computer program has a set of strict rules to decide the flow of program execution. C++ Syntax The syntax is a layout of words, expression, and symbols. Well, it's because an email address has its well-defined syntax. You need some combination of letters, numbers, potentially with underscores (_) or periods (.) in between, followed by an at the rate (@) symbol, followed by some website domain (company.com). So, syntax in a programming language is much the same. They are some well-defined set of rules that allow you to create some piece of well-functioning software. But, if you don't abide by the rules of a programming language or syntax, you'll get errors. C++ Tools In the real world, a tool is something (usually a physical object) that helps you to get a certain job done promptly. Well, this holds true with the programming world too. A tool in programming is some piece of software which when used with the code allows you to program faster. There are probably tens of thousands, if not millions of different tools across all the programming languages. Most crucial tool, considered by many, is an IDE, an Integrated Development Environment. An IDE is a software which will make your coding life so much easier. IDEs ensure that your files and folders are organized and give you a nice and clean way to view them. Types of C++ Errors Another way to look at C++ in a practical sense is to start enumerating different kinds of errors that occur as the written code makes its way to final execution. First, there are syntax errors where the code is actually written in an illegible way. This can be a misuse of punctuation, or the misspelling of a function command or anything else that compromises the integrity of the syntax as it is written. Another fundamental type of error is a compiler error that simply tells the programmer the compiler was not able to do its work effectively. As a compiler language, C++ relies on the compiler to make the source code into machine readable code and optimize it in various ways. A third type of error happens after the program has been successfully compiled. Runtime errors are not uncommon in C++ executables. What they represent is some lack of designated resource or non-working command in the executable program. In other words, the syntax is right, and the program was compiled successfully, but as the program is doing its work, it encounters a problem, whether that has to do with interdependencies, operating system requirements or anything else in the general environment in which the program is trying to work. Over time, C++ has remained a very useful language not only in computer programming itself, but in teaching new programmers about how object oriented programming works.

Enhanced AZ-104 Anki deck targeting critical weak areas (App Service & Containers 20% failure rate)

The ThingSay Mobile Application is a smart IoT-based mobile app developed to monitor and manage greenhouse environments in real time. The application connects to greenhouse sensors and backend services to display critical environmental parameters such as temperature, humidity, light intensity (lux), air pressure, wind speed, and air quality.

A modern, open-style workflow automation platform — visually compose, execute, and monitor business-critical automations across apps, APIs, and AI services from one workspace.

This serves as a repository for the android app built by the GoTeam during Hover's organized #GizaHackathon. It is an app that leverages the Hover SDK for processing USSDs to execute common and critical financial services needed immensely by the general public

Conducted backend requirements analysis & designed test cases for Order and Go app. Identified 11 bugs: 3 (27%) in payment method, 5 (45%) preventing transport service cancellation, others due to requirement limit violations—totaling 72% critical issues affecting core functionality. All reported via Jira for resolution.

The app provides users with quick access to emergency service numbers (police, fire, ambulance, etc.) for all countries around the world. Users can easily search for a country and view the essential emergency contacts, ensuring they have critical information at their fingertips while traveling or living abroad.

This project, titled "Creating a Chatbot in Python," addresses the critical need for enhancing customer service and user experience on websites and applications. In today's digital landscape, customers have high expectations for prompt and effective assistance when they encounter issues or questions while using an app or website. Failing

CovidApp-by eYRC#1804 -(Android application) An attempt to connect the frontline warrior to people at root level PROBLEM ADDRESSED: Several studies show that India’s testing strategy lacks in many ways which may increase the number of COVID-19 patients enormously. The main problem that we have addressed in our idea is that India is not doing enough testing that could help it trace and treat infected patients and contain the spread of the disease. It also involves finding a solution of the human tendency not to reveal their symptoms which is a critical issue. In this solution, we have tried to fight against the disease at a community level involving the local police, the private doctors and the people. DESCRIPTION: Our solution to the above problem is a native mobile application which mainly uses Firebase for backend services. The application consists of two broad sections that is people and the police of a particular area. Our aim is to make full use of the people in the medical field to ensure more and more testing. Thus, in our application we identify the available private hospitals for checking common symptoms of covid-19 who in turn will suggest them for immediate testing or a period of self-quarantine. This has been done by using Google Map API services. People who experience symptoms can simply login to the application, connect to a private hospital providing their basic information and we connect them to the nearest doctors. The app uses Firebase Realtime Database to store and sync this information which can later be analyzed. The app also includes a separate section where people of a community connect to the police of the area to inform them about a suspected case or any kind of problem (e.g. Crowding) the community faces. To eliminate false information, we use Firebase Authentication feature for the informants. To encourage the participations of more people in medical field to participate in this fight, we also have a local chat messaging feature through which people who login can talk to specified consultants for information and procced for further decisions of a checkup. HARDWARE AND SOFTWARE REQUIREMENT: Since it is an application for android, there is no such hardware requirement. For user, they need an android based mobile device (version 4.0 and above). And for government, they need an infrastructure to felicitate the flow to data. PROCESS FLOW: Currently, on our main screen there is an option for login as police or login as citizen. This is only for demonstration purpose. This could be two app, one only for citizens where they can register their complains and chat a medical representative and the second app will be for police where they could login through their login ID and see the complains of their area. """""""""Police Login can only be logged in by using some authenticated police id and name for now we have used 10 dummy police id to just show the process of authentication... To Login and see the complains in this prototype you can use---> (police name->arun kumar) (police id-> 800123) (police area under surveillance->ashok nagar)""""""""" """""""""for login into citizen you can register a new user or u can use our dummy user who is (email-id->user@gmail.com) (password->user123)""""""""

Create a website and app that will service “angels” and “survivors” before a hurricane and in the critical 24 hours immediately after.

Create a website and app that will service “angels” and “survivors” before a hurricane and in the critical 24 hours immediately after.

This app is a critical solution designed to streamline and optimize the process of requesting and dispatching ambulance services in times of medical emergencies through an app

HelpHive is a comprehensive support system for victims of violence and harassment. Our mobile app enables victims to register cases online and access critical support services.

A centralized dashboard that continuously monitors the health and status of our critical services, including the SFTP Service, Restless Web Service, and Web App. This page provides real-time alerts and notifications to ensure prompt response to any service disruptions or issues, helping maintain seamless operations.

An AI-powered mobile app that helps farmers diagnose crop diseases, plan cultivation, and access critical agri-services built with React Native (Expo), on-device TFLite inference, and Gemini-powered insights.