Applications ("apps"), which extend the functionality of devices, are written using the Android software development kit (SDK)[75] and, often, the Java programming language.
Java may be combined with C/C++,together with a choice of non-default runtimes that allow better C++ support.[78] The Go programming language is also supported, although with a limited set of application programming interfaces (API).
The SDK includes a comprehensive set of development tools,[80] including a debugger, software libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. Initially, Google's supported integrated development environment (IDE) was Eclipse using the Android Development Tools (ADT) plugin; in December 2014, Google released Android Studio, based on IntelliJ IDEA, as its primary IDE for Android application development. Other development tools are available, including a native development kit (NDK) for applications or extensions in C or C++, Google App Inventor, a visual environment for novice programmers, and various cross platform mobile web applications frameworks. In January 2014, Google unveiled an framework based on Apache Cordova for porting Chrome HTML 5 web applications to Android, wrapped in a native application shell.