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3 questions · 5 marks
Binary, denary and hexadecimal patterns represent numbers.
Convert the binary pattern 1110 1100 to denary.
Award one mark for:
236
Why: Correct: 128 + 64 + 32 + 8 + 4 = 236 (1).
55
Why: Reads the place values from the wrong end (the left-hand bit as 1), so the value is wrong.
5
Why: Counts the 1s instead of adding their place values.
Computers manipulate binary patterns.
Convert the hexadecimal number 1F to 8-bit binary.
Award one mark for each correct nibble in the correct order:
0 marks if the response is not 8-bit binary.
0001 1111
Why: Each digit is 4 bits: 1 = 0001, F = 1111 (2).
0001 0000
Why: Converts F as if it were the next digit up. The first nibble is correct (1); the second is not.
1111 0001
Why: The nibbles are in the wrong order. Neither nibble is correct.
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 |
Award one mark for each correct nibble in the correct order:
0 marks if the response is not 8-bit binary.
1101 0111
Why: 184 + 31 = 215, carrying where a column adds to 2: both nibbles are correct (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.
1011 1111
Why: Writes 1 in every column with a 1 and never carries. Neither nibble is correct.
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