Java is a programming language. Java differs from most other programming languages in that programs written in Java can generally be run on many different types of computers, not only the type of computer it was written on. This is because Java is run in what is known as a runtime environment- a separate program that interprets the Java code. Runtime environments are specific to the machine being used. Any computer (or other device, such as a cellphone) that has a Java runtime environment can run Java code, assuming that the runtime environment supports the version of the code the program was written in.
Java was invented by Sun Microsystems with the intention of creating a "Write once, run anywhere" programming language. The first release, Java 1.0, was not quite as interoperable across platforms as expected, which led to the joke "Write once, debug everywhere". Also, as the code had to be interpreted, programs written in Java ran slowly compared to other languages. The current version addresses these issues and adds new functionality, making Java one of the most popular and supported programming languages on personal computers, cellphones, PDA's, and other small devices. Recently, Java was released under the GPL open source licence.
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