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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.
High-level code can be translated by a compiler or by an interpreter.
Describe how a compiler translates high-level code differently from an interpreter.
Award up to two marks for a linked description such as:
Accept the compiler point and the interpreter point in either order.
Do not accept responses about object code/executable files, when the translated code is executed, how errors are reported, or speed/memory use.
Do not accept 'the interpreter executes/runs each line' on its own, without saying that it translates one line/statement at a time.
A compiler translates the whole program in one go, while an interpreter translates one line at a time.
Why: Whole program translated in one go (1) and interpreter translates one line at a time (1).
A compiler translates the whole program in one go.
Why: Whole program translated in one go (1); no linked point about the interpreter translating a line at a time.
A compiler produces an executable file, but an interpreter does not.
Why: Describes the output, not the amount translated at a time; object code/executable files are not accepted.
Computer systems manipulate bit patterns.
Convert the denary number 140 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.
1000 1100
Why: 140 = 128 + 8 + 4: both nibbles are correct (2).
1000 1101
Why: Converts 141 instead (a slip in adding up the place values). The first nibble is correct (1); the second is not.
0011 0001
Why: The bits are written in reverse, smallest place value first. Neither nibble is correct.
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