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2 questions · 3 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.
A solid state drive has a capacity of 5 gibibytes.
Give an expression to calculate the number of bits in 5 gibibytes. You do not need to do the calculation.
Award one mark for each of:
Accept 5 × 1 073 741 824 × 8.
Accept 5 × 2^33 or 42 949 672 960 as a fully correct expression (2 marks).
Do not accept 5 × 1000^3 × 8, which uses decimal multiples.
Do not accept ÷ 8, which converts bits to bytes.
8 × 5 × 2^30
Why: 5 × 2^30 is the number of bytes (1) and × 8 converts bytes to bits (1).
5 × 2^30
Why: Correct number of bytes using the binary multiple 2^30 (1), but no conversion to bits.
5 × 1000^3 × 8
Why: Uses decimal 1000^3 instead of binary 1024^3, so the expression is not fully correct; no creditworthy point.
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