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3 questions · 5 marks
Computers manipulate binary patterns.
Convert the binary pattern 1010 0100 to denary.
Award one mark for:
164
Why: Correct: 128 + 32 + 4 = 164 (1).
37
Why: Reads the place values from the wrong end (the left-hand bit as 1), so the value is wrong.
3
Why: Counts the 1s instead of adding their place values.
Binary patterns can represent numbers.
Convert the 8-bit binary two's complement pattern 1111 1001 to denary.
Award one mark for each of:
The correct answer is −7
−7
Why: The left-hand bit is worth −128: −128 + 121 = -7. Sign (1) and value (1).
7
Why: The value is right (1) but the minus sign is missing.
249
Why: Reads it as an unsigned number, so neither the sign nor the value is right.
Binary patterns can represent numbers.
Convert the hexadecimal number D3 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.
1101 0011
Why: Each digit is 4 bits: D = 1101, 3 = 0011 (2).
1101 0100
Why: Converts 3 as if it were the next digit up. The first nibble is correct (1); the second is not.
0011 1101
Why: The nibbles are in the wrong order. Neither nibble is correct.
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