Compiler

A compiler is a computer program which translates source code written in a high-level programming language into executable machine code. The act of doing this is called compilation.

Outline of the compilation process

In the freely available online book "Basics of Compiler Design", Professor Torben Mogensen identifies seven phases within a compiler, with the various phases being performed in one or more passes over the program. A diagram illustrating these (and other optional optimisation) phases is shown on the last page of Professor Frank Pfenning's "Lecture Notes on Compiler Design: Overview"

Lexical analysis: convert the source code into a sequence of tokens, such as variable names, keywords, numbers, and special symbols such as '+'.

Syntax analysis or parsing: arrange the tokens into a parse tree or syntax tree which represents the structure of the program.

Semantic analysis: annotate the parse tree with semantic actions, and perform various consistency checks.

Intermediate code generation: use the annotated parse tree to generate code in some simple machine-independent intermediate language.

Register allocation: map the symbolic names used in the intermediate code on to the registers available in the target machine.

Assembly code generation: translate the intermediate code into assembly language for the target machine.

Assembly and linking: translate the assembly language into executable machine code.