Translators
What is a translator?
- A translator is a program that translates program source code into machine code so that it can executed directly by a processor
- Low-level languages such as assembly code are translated using an assembler
- High-level languages such as Python are translated using a compiler or interpreter
What is an assembler?
- An assembler translates mnemonics written in assembly language (low-level) in to machine code
- Each lime of assembly language is assembled into a single machine code instruction
- Assemblers have been used less and less since high-level languages were introduced
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Speed of execution |
Difficult to write due to limited and hard to understand commands |
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Optimises the code |
Changes mean it must be reassembled |
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Original source code will not be seen |
Designed solely for one specific processor |
What is a compiler?
- A compiler translates high-level languages into machine code all in one go
- Compilers translate inputs into machine code directly
- Compilers are generally used when a program is finished and has been checked for syntax errors
- Compiled code can be distributed (creates an executable) and run without the need for translation software
- If compiled code contains any errors, after fixing, it will need re-compiling
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Speed of execution |
Can be memory intensive |
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Optimises the code |
Difficult to debug |
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Original source code will not be seen |
Changes mean it must be recompiled |
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It is designed solely for one specific processor |
What is an interpreter?
- An interpreter translates high-level languages into machine code one line at a time
- Each line is executed after translation and if any errors are found, the process stops
- Interpreters do not generate machine code directly, appropriate machine code subroutines are called
- Interpreters are generally used when a program is being written in the development stage
- Interpreted code is more difficult to distribute as translation software is needed for it to run
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Stops when it finds a specific syntax error in the code |
Slower execution |
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Easier to debug |
Every time the program is run it has to be translated |
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Require less RAM to process the code |
Executed as is, no optimisation |
Worked example
A computer program is written in a high-level programming language.
(a) State why the computer needs to translate the code before it is executed.[1]
(b) Either a compiler or an interpreter can translate the code. Describe two differences between how a compiler and an interpreter would translate the code.[2]
How to answer this question
- (a) what time of language does a computer understand?
- (b) the keyword is 'how'
Answer
(a)
- To convert it to binary/machine code
- The processor can only understand machine code
(b)
- Compiler translates all the code in one go...
- ...whereas an interpreter translates one line at a time
- Compiler creates an executable...
- ...whereas an interpreter does not/executes one line at a time
- Compiler reports an error at the end...
- ...whereas an interpreter stops when it finds an error
