UNIX for Advanced & Expert Users

I am testing some utilities of Unix. I want to know what difference will it make when i test this utilities on a 32 bit operating system and a 64 bit operating system.
Will the command line arguments increase on a 64 bit OS. Will the datatype range increase. DO i need to check with large files??. I have some of these basic doubts. If somebody has experience regarding the same please reply.

Yeah, the C numeric types range will increase. But this shouldn't cause problems if you write portable C code. But I admit this can be hard to do. Especially if all the testing was done on a specific architecture. But you shouldn't worry about the OS functions.