Computer systems manipulate bit patterns.
Convert the 8-bit binary two's complement pattern 1000 0111 to denary.
Mark scheme
Award one mark for each of:
- − (negative sign) (1)
- 121 (1)
The correct answer is −121
Example answers and how they were marked
Full marks2/2
−121
Why: The left-hand bit is worth −128: −128 + 7 = -121. Sign (1) and value (1).
Some marks1/2
121
Why: The value is right (1) but the minus sign is missing.
No marks0/2
135
Why: Reads it as an unsigned number, so neither the sign nor the value is right.