6. Overflow Condition, Cont

• Computers don't know the difference between signed and unsigned binary numbers.

• This is a good thing, because it makes logic circuits fast.

• This is also a bad thing, because distinguishing between signed and unsigned becomes programmer's responsibility.

• Distinction between signed and unsigned data types is very important when detecting an overflow after addition or subtraction.

• Correct approach to detect the overflow is to consider two separate cases:

  1. Overflow when adding signed numbers is indicated by the overflow flag, OF.

  2. Overflow when adding unsigned numbers is indicated by the carry flag, CF.