Programming languages & translators – GCSE Computer Science exam questions with mark scheme

1Grade 1–33 marks

(a) Give one example of a low-level language. [1]

(b) Give two reasons why most programs are written in high-level languages. [2]

(a) Machine code / assembly language; accept assembly code; reject 'assembler' (a translator, not a language); reject 'binary' on its own(1)
(b) One reason from: easier to read / write / understand (English-like keywords); easier to debug / maintain; not specific to one processor / portable (can be translated for different processors); one statement does the work of several machine instructions, so programs are quicker to write(1)
(b) A second, different reason from the list above(1)
Answer: (a) Assembly language (b) e.g. easier to understand; portable across processors
Examiner tip: Name a type of low-level language (machine code or assembly language) – 'assembler' is the translator, not the language.

2Grade 4–54 marks

(a) State the type of translator that:

(i) converts assembly language into machine code [1]
(ii) translates a whole high-level program into machine code in one go, producing an executable file [1]
(iii) translates and runs a high-level program one line at a time. [1]

(b) State why a program written in a high-level language must be translated before it can be run. [1]

(a)(i) Assembler(1)
(a)(ii) Compiler(1)
(a)(iii) Interpreter(1)
(b) The processor / CPU can only execute (understand) machine code / binary instructions; accept 'the computer only understands binary'(1)
Answer: (i) Assembler (ii) Compiler (iii) Interpreter (b) processors can only execute machine code
Examiner tip: Interpreters translate and run line by line, but they do not produce an executable file.

3Grade 4–53 marks

A student is learning to program and uses an interpreter while developing their code.

(a) Explain one reason why an interpreter is useful while a program is being developed. [2]

(b) State one disadvantage of running a finished program with an interpreter rather than as compiled code. [1]

(a) Point: the interpreter stops at the first error and shows which line it is on; accept: the program can be run / tested straight away without waiting for the whole program to be compiled(1)
(a) Expansion linked to the point: so the error can be found and fixed quickly / the student can test small parts as they write them(1)
(b) Runs more slowly (each statement must be translated every time it is run); accept: the interpreter must be installed on the computer that runs it; the source code has to be given to the user(1)
Answer: (a) It stops at the line with the error, so errors are found quickly. (b) Slower execution.
Examiner tip: 'Explain' questions need a point and a reason. 'It is easier' on its own gets nothing.

4Grade 6–74 marks

(a) Describe the relationship between assembly language instructions and machine code instructions. [1]

(b) State why a machine code program written for one type of processor may not run on a different type of processor. [1]

(c) Give two situations where a programmer might choose to use a low-level language rather than a high-level language. [2]

(a) Each assembly language instruction corresponds to / translates into one machine code instruction (one-to-one); accept 'each mnemonic represents one machine code instruction'(1)
(b) Machine code is specific to a processor (family) / different processors have different instruction sets(1)
(c) One situation from: directly controlling / accessing hardware (e.g. writing a device driver); programming an embedded system (e.g. in a washing machine); when memory is very limited so the code must be as small as possible; when the program must execute as fast as possible (performance-critical code)(1)
(c) A second, different situation from the list above. Unqualified 'faster' and 'more efficient' count as one point; do not give two marks where the second answer only repeats the first (e.g. 'embedded system' then 'because embedded systems have little memory')(1)
Answer: (a) One-to-one (b) instruction sets differ between processors (c) e.g. controlling hardware directly; embedded system with limited memory
Examiner tip: Give two clearly different situations: an unqualified 'it runs faster' and 'it is more efficient' count as the same point.

5Grade 6–74 marks

A games company has written a new game in a high-level language. It will sell the game to customers to download.

Explain two reasons why the company should use a compiler, rather than an interpreter, for the version of the game that it distributes. [4]

First reason identified, from: the compiler produces an executable (machine code) file; compiled code runs faster (it is not translated every time it runs); the source code does not have to be given out(1)
Expansion matching the first reason: (executable) customers do not need an interpreter / translator or the source code to run the game; (faster) a game must respond quickly / run smoothly; (source code) others cannot easily copy / change the game, protecting the company's work(1)
Second, different reason from the list above(1)
Expansion matching the second reason, as above. Max 2 marks per reason; the expansion must be linked to its own reason(1)
Answer: Executable needs no translator for customers; compiled code runs faster; source code stays private.
Examiner tip: Each reason needs its own 'so…' expansion that relates to the game or customers to earn the second mark.

6Grade 8–96 marks

An engineering company is developing two pieces of software:

the control program for a small embedded system inside a washing machine, which has very limited memory
a desktop app that customers can install on Windows and macOS computers to book repairs.

Discuss the choice of programming language level (high-level or low-level) and the type of translator the company could use for each piece of software. [6]

Low-level / assembly language for the washing machine: gives direct control of the hardware (e.g. motor, sensors)(1)
Low-level code can be made to use very little memory and run quickly, which suits limited embedded hardware(1)
An assembler would be needed to translate assembly code into machine code for that processor(1)
High-level language for the desktop app: quicker to write, easier to read, debug and maintain (e.g. by a team)(1)
High-level code is portable: the same source can be compiled for different processors / operating systems (Windows and macOS)(1)
A compiler suits distribution: produces an executable, customers don't need a translator, source code is protected, runs faster. An interpreter may be used during development to find errors quickly(1)
Counter-point: the washing machine could also use a high-level language with a compiler, trading some memory/speed efficiency for faster development(1)

Level	Marks	What it looks like
Level 3	5–6	Clear, well-reasoned discussion of both programs. Language level and translator are justified for each, with explicit links to the scenario (memory limits, hardware control, two operating systems, distribution to customers).
Level 2	3–4	Sensible choices for both programs with some justification, or a detailed justification for one program only. Some links to the scenario.
Level 1	1–2	Limited points made, e.g. features of high- or low-level languages or translators stated with little or no reference to the scenario.
Level 0	0	Nothing worthy of credit.

Answer: Washing machine: low-level/assembly + assembler (hardware control, small memory). Desktop app: high-level + compiler (portable, maintainable, executable for customers).
Examiner tip: Make a decision for each piece of software and justify it. Listing features of languages without linking them to the scenario keeps you in Level 1.

7Grade 6–75 marks

(a) Give two differences between a compiler and an interpreter. [2]

(b) State why an assembler is needed. [1]

(c) The computer that controls a washing machine is an embedded system. Explain what is meant by an embedded system. [2]

(a) Any two differences from (1 mark each; each must describe both translators, or be clearly comparative): compiler translates the whole program in one go, interpreter translates and executes one line / instruction at a time; compiler produces machine code / an executable (object code) file, interpreter does not (it calls its own machine-code subroutines); compiled program can run without the translator, interpreted program needs the interpreter every time it runs; compiled code runs faster than interpreted code; interpreter stops at the first error found, compiler reports errors after translating the whole program; compiled program can be distributed without the source code, interpreted program needs the source code to run; interpreted code is easier to test / debug during development because errors are reported (and can be fixed) line by line without recompiling, compiled code must be recompiled after each change; a compiled executable only runs on the type of processor / platform it was compiled for, interpreted source code can run on any computer that has a suitable interpreter. First difference(1)
(a) Second, different difference from the list above(1)
(b) To translate assembly language (code) into machine code (so the processor can execute it); accept binary / object code for machine code; must refer to assembly language, not just 'low-level' or 'high-level' code(1)
(c) A computer system built into / inside a larger device(1)
(c) Which has a dedicated / single / specific function (e.g. controlling the wash cycle); allow 'only does one job' / 'is not general-purpose'(1)
Answer: (a) e.g. whole program vs line by line; compiler produces machine code/executable, interpreter does not (b) translates assembly language into machine code (c) a computer system built into a larger device, with a dedicated function
Examiner tip: Each difference must say what BOTH translators do – one-sided answers lose the mark.

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