Practice question · Select all that apply
Each option is an addition performed in an 8-bit UNSIGNED register. Select every one that overflows.
Hints
- Compute each true sum, then compare it with the largest value eight unsigned bits can hold.
- The boundary is 255: a sum of exactly 255 is fine, a sum of 256 is not.
Show the answer
- A. 200 + 100
- B. 255 + 1
- D. 240 + 16
Why
200 + 100 = 300, 255 + 1 = 256 and 240 + 16 = 256 all exceed 255 and wrap. 128 + 127 = 255 fits exactly, and 100 + 100 = 200 fits easily. The tempting error is 128 + 127, which looks like it should overflow because both numbers are large, but the boundary is about the sum, not the operands.
Practise Arithmetic at Machine Level
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