CPE 315/353
Professor Stearns
Why do Carry and Overflow Exist?

This table summarizes the purpose of the Carry and Overflow bit in computer arithmetic.


  Carry bit Overflow bit
Unsigned numbers Error flag or
Multiple precision arithmetic 		None
2's complement numbers Multiple precision arithmetic Error flag


MIPS cpu notes

  1. The MIPS 2000 (our textbook cpu) provides no support for multiple precision arithmetic.
  2. The arithmetic instructions have two versions - one version checks for overflow and causes an exception.
  3. The ALU doesn't distinguish between 2's complement and unsigned operations; they are identical.
Last updated on 9/24/02