This is determined by the calling convention [0]. If you're interacting with code that you didn't write, you need to know the calling convention that they use i

This is determined by the calling convention [0]. If you're interacting with code that you didn't write, you need to know the calling convention that they use in order to set up arguments correctly. 0: https://en.wikipedia.org/wiki/X86_calling_conventions https://en.wikipedia.org/wiki/X86_calling_conventions