Platform-Independent

A platform-independent program is one that functions without regard to your type of computer system or operating system. "Platform" can either refer to your type of computer (i.e., Macintosh or PC) or to the operating system that your computer is running. "Cross-platform" and "inter-platform" software--software that can function on a variety of platforms--is very hot now, especially with the growth of PowerPC technology.

URLs:

Why Macintosh

Apple offers you their opinions on why you should choose their platform.

IBMlink

IBM tells you why you should buy one of their platforms

W3E References:

computing platform

OS (operating system)