Translators Aqa

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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

Advantages	Disadvantages
Speed of execution	Difficult to write due to limited and hard to understand commands
Optimises the code	Changes mean it must be reassembled
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

Advantages	Disadvantages
Speed of execution	Can be memory intensive
Optimises the code	Difficult to debug
Original source code will not be seen	Changes mean it must be recompiled
	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

Advantages	Disadvantages
Stops when it finds a specific syntax error in the code	Slower execution
Easier to debug	Every time the program is run it has to be translated
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 type 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

Computer Science GCES AQA