What is the difference between low-level and high-level languages, and how does an interpreter differ from a compiler?
Understand the characteristics and purposes of low-level and high-level programming languages, and how an interpreter differs from a compiler in the way it translates high-level code into machine code.
A focused answer to Edexcel GCSE Computer Science 3.3.1 and 3.3.2, covering the characteristics of low-level and high-level programming languages and the difference between a compiler and an interpreter.
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What this dot point is asking
Edexcel wants you to describe the characteristics and purposes of low-level and high-level programming languages, and to explain how a compiler differs from an interpreter in the way it translates high-level code into the machine code the processor runs.
Low-level languages
Low-level languages are hard for people to read and write because they deal with individual processor instructions and memory addresses, but they give precise control over the hardware and can be very efficient. They are processor-specific, so code written for one type of CPU will not run on a different one. Their purpose is tasks needing direct hardware control or maximum efficiency, such as device drivers or embedded systems.
High-level languages
The advantages Edexcel rewards are ease of use and portability. High-level code is far quicker to write and understand, and one high-level statement usually corresponds to many machine-code instructions, so programs are shorter. It is portable: the same program can run on different types of computer once it has been translated for each, because it is not tied to one processor. The trade-off is slightly less direct control over the hardware and a translation step. Most software is written in high-level languages for these reasons.
Translators: compilers and interpreters
The core difference is all-at-once versus line-by-line. After compiling, you have a standalone executable that runs quickly and without the source code or the compiler, but you must recompile the whole program after any change. An interpreter runs the source directly, translating each line as it reaches it, so the program starts immediately and you do not produce an executable.
Comparing compilers and interpreters
Why translation is needed at all
The processor can only execute machine code (binary), but people write in high-level languages for speed and clarity. A translator bridges the gap. Edexcel's Paper 2 uses Python, which is normally interpreted, which is one reason it is convenient for learning and for the onscreen exam: you can run and test code immediately. Knowing both why high-level languages are used and how the two translators differ lets you answer the common "which would you use and why" questions.
Try this
Q1. State one advantage of a high-level language over a low-level language. [1 mark]
- Cue. Any one of: easier to read, write and debug; portable across different computers; shorter programs.
Q2. State the main difference between how a compiler and an interpreter translate a program. [1 mark]
- Cue. A compiler translates the whole program at once into an executable; an interpreter translates and runs it one statement at a time.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20224 marksExplain two differences between a high-level programming language and a low-level programming language.Show worked answer →
Give two contrasting pairs of points.
First, a high-level language uses English-like keywords and is easier for people to read, write and debug, whereas a low-level language (machine code or assembly) is closer to the binary the processor uses and is much harder for people to understand.
Second, a high-level language is portable, so the same program can run on different types of computer once translated, whereas low-level code is specific to one type of processor. (A further difference: one high-level statement usually translates into many machine-code instructions.)
Markers reward two developed differences, each a genuine contrast: readability or ease of use, portability, and closeness to the hardware. Each point must compare the two.
Edexcel 20214 marksDescribe one difference between how a compiler and an interpreter translate a high-level program, and state one advantage of using an interpreter during program development.Show worked answer →
A compiler translates the whole program into machine code in one go, producing an executable file that is then run; an interpreter translates and runs the program one statement (line) at a time, with no separate executable produced.
An advantage of an interpreter during development is that it stops at the first error it reaches and reports it, which makes finding and fixing errors quicker and lets you test code as you write it, without recompiling the whole program each time.
Markers reward the translation difference (whole program at once versus line by line) and a valid development advantage of an interpreter (easier debugging, runs immediately without a full recompile).
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Computer Science (1CP2) specification — Pearson (2020)