In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. Typical platforms include a computer's architecture, operating system, or programming languages and their runtime libraries.
Hardware, operating system and virtual machine
In relation to hardware, platform often describes the set of hardware components that make up the computer itself that the software is written to target to (often just described as "written for an architecture"). Pure assembly language can be run on this hardware platform, but most commonly, operating system software is written to target the hardware platform, but in doing so, becomes a platform in itself, facilitating the running of other software that is used to target the operating system, and likewise the hardware architecture. Furthermore, software that is written for the operating system can be used to support the running of other software: for example a virtual machine (which targets a certain operating system/hardware) that is used to run other programs that are written for that virtual machine, which constitutes another platform.
Java programs are a typical example of the latter point. Java source code is "compiled" to an intermediate-language bytecode which is then interpreted by an interpreter,the JVM, which then interfaces that program with the Java software libraries. In phones, PDAs and other wireless mobile devices, these libraries are the J2ME.Some phones, even with out a full fledged OS, enable Java programs such as games to operate. Java and the bytecode are said to be platform independent. But this is because Java is the platform as well as a programming language. Software really can not operate without a platform or be platform independent. The programming language is referred to here, meaning, the programmer need not be concerned about the platform, nor will the language change with a different platform.
See also Java Platform
Role in software
A platform is a crucial element in software development. A platform might be simply defined as 'a place to launch software'. Platforms are frequently mentioned with APIs. A complete suite of APIs constitute another type of platform. Platform frequently are referred to as operating systems as defined above. However they are not always the same thing. For example, 2 other popular non-OS platforms are Java, as mentioned above, and BREW for mobile phones.