Build a practice paper from 631 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.
4 questions · 7 marks
Computers manipulate binary patterns.
Convert the binary pattern 1110 0000 to denary.
Award one mark for:
224
Why: Correct: 128 + 64 + 32 = 224 (1).
7
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.
A programmer has written a program in assembly language.
Describe why it is necessary to translate the program into machine code before it can be run.
Award up to two marks for a linked description such as:
Do not accept 'assembly language is a low-level language'.
Do not accept 'it is hard to understand' or 'it is not English'.
Do not accept benefits, such as 'machine code runs faster' or 'the program will run more quickly'.
Do not accept 'an assembler/a translator converts it' on its own, with no reference to the processor only being able to execute machine code/binary.
Do not accept responses about high-level languages or about compilers/interpreters.
The processor can only execute machine code, so the assembly instructions must be converted into machine code before the program can run.
Why: States what the processor can execute (1) and links it to converting the program's instructions into machine code (1).
Each assembly instruction matches one machine code instruction.
Why: Correct point about the one-to-one match (1) but no development saying that this is because the processor only executes machine code.
Because an assembler translates assembly language into machine code.
Why: Names the translator but gives no reason tied to the processor only being able to execute machine code, so no mark; this is in the 'Do not accept' guidance.
Binary patterns can represent numbers.
Convert the denary number 199 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.
1100 0111
Why: 199 = 128 + 64 + 4 + 2 + 1: both nibbles are correct (2).
1100 1000
Why: Converts 200 instead (a slip in adding up the place values). The first nibble is correct (1); the second is not.
1110 0011
Why: The bits are written in reverse, smallest place value first. Neither nibble is correct.
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