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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.
A computer can be used by more than one person.
Describe how an operating system uses access rights to protect each user's files.
Award up to two marks for a linked description such as:
Do not accept responses about asking for a password/username, as this checks who the user is, not what they are allowed to do.
Do not accept 'files are protected/safe' or 'access rights protect files' without saying how access is limited (e.g. read-only access, permissions for different users).
A user can be given read-only access to a file, so they can open it but cannot edit or delete it.
Why: Read-only/read access point (1) and linked development that the user cannot edit/delete the file (1).
A user can be given read-only access to a file.
Why: Read-only/read access point (1); no development saying what this prevents, such as being unable to edit/delete the file (0).
The operating system asks for the password again before the file opens.
Why: Describes asking for a password, which checks who the user is, not access rights to the file; no creditworthy point.
Source code can contain syntax errors.
Describe how a compiler and an interpreter differ in the way they deal with syntax errors.
Award up to two marks for a linked description such as:
Do not accept answers about fixing/correcting errors or about object code.
Do not award 'the compiler finds more errors' without saying errors are reported at the end.
A compiler reports all the syntax errors at the end of translation, whereas an interpreter stops and reports the error as soon as it finds one.
Why: Compiler reports errors at the end (1) and interpreter stops/reports at the first error (1).
An interpreter stops translating when it finds a syntax error.
Why: Interpreter stops at the first error (1); no comparison with when the compiler reports errors.
A compiler reports a syntax error immediately, before translating the rest of the program.
Why: Reverses the compiler's behaviour; it finishes translating before reporting errors.
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