There is just c which is major but it is not really crossplatform. in case that you want it to execute in other platform than where you develop /build your application , you need to recompile it for other platform.
also all libraries that are avaiable for c/c++ are not crossplatform , some of them are available in some platforms and some other are not avaiable.
An open source project that now is owned by Novell port some part of .net class libraries , CLI ... which allows you to execute .net application on Linux but that is not really guaranteed.
Most languages are platform-independent, in the sense that you can run a program written in them on many platforms: C, C++, Ruby, Python, Perl, Smalltalk, and many more. Some of these need to be compiled separately for each platform, and some of them have libraries that are not the same on every platform. Any Microsoft language product, for example, includes Windows-only libaries. Still, there are many languages -- Ruby, Python, Perl -- with reasonably portable libraries and which don't need to be compiled on each platform. These really rival Java for portability, although Java is much faster than any of these.
But the idea of a "platform dependent language" is a rather antiquated one. The real platform-dependent languages like PL/I, the many flavors of Lisp, COBOL, etc, have been relegated to the background these days. All languages now in common use are portable at least to some extent.
REXX is an ANSI standard langauge. There are interpreters on all IBM mainframe and distributed OS platforms, Windows, most Unix platforms and the Commodore Amiga. Code that uses only standard features generally runs on any platform.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi