Computer systems manipulate bit patterns.
Complete the table to show the result of the 8-bit binary addition.
| 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
|---|---|---|---|---|---|---|---|
| 1 | 0 | 1 | 1 | 1 | 0 | 0 | 0 |
| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 |
Mark scheme
Award one mark for each correct nibble in the correct order:
- 1101 (1)
- 0111 (1)
0 marks if the response is not 8-bit binary.
Example answers and how they were marked
Full marks2/2
1101 0111
Why: 184 + 31 = 215, carrying where a column adds to 2: both nibbles are correct (2).
Some marks1/2
1010 0111
Why: Writes 0 for 1 + 1 but forgets to carry the 1. The second nibble is correct (1); the first is not.
No marks0/2
1011 1111
Why: Writes 1 in every column with a 1 and never carries. Neither nibble is correct.