Translators

This lesson covers the three types of language translator — compilers, interpreters and assemblers — and the stages of compilation. The OCR H446 specification requires you to understand how each translator works, compare them, and describe the stages of the compilation process.

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Why Translators Are Needed

Computers can only execute machine code (binary). Programmers write code in high-level languages or assembly language, which must be translated into machine code before the CPU can run it.

Source Language	Translator	Target
Assembly language	Assembler	Machine code
High-level language	Compiler	Machine code (executable file)
High-level language	Interpreter	Machine code (executed line by line)

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Assemblers

An assembler translates assembly language into machine code.

Feature	Detail
Input	Assembly language source file
Output	Machine code (object file)
Translation	One-to-one — each assembly mnemonic maps to exactly one machine code instruction
Passes	Most assemblers are two-pass: the first pass builds a symbol table (mapping labels to addresses); the second pass generates machine code using the symbol table