Example Program

Say that you have been given this task:

Write a subroutine that computes the maximum of its two integer arguments. The integers use two's complement representation. Use stack-based linking.

In C, the subroutine prototype would look like this:

int maxInt(int x, int y);

With our stack-based linkage convention this is:

Subroutine maxInt
  Input:   $a0 -- a two's complement integer
           $a1 -- a two's complement integer
  Returns: $v0 -- the maximum of the two integers

The subroutine must be written with no knowledge of what is in any register other than $ra, $a0, and $a1. Indeed, since the subroutine might be used in many different programs, the contents of the other registers cannot be known.