The Cross-platform reference article from the English Wikipedia on 24-Apr-2004
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Cross-platform

A cross-platform is a programming language, software application or hardware device that works on more than one system platform (e.g. Unix, Windows, Macintosh). Examples of cross-platform languages are C, C++, Java, JavaScript, Perl, Python, REALbasic programming language, and the Revolution programming language.

There are also cross-platform extensions for many programming languages that enable programmers to compile/run the same source code with minimal fixes on different platforms. An example is wxWindows.