Question

By concept/function/implementation, what are the differences between compilers and parsers?

Answer 1

A compiler is often made up of several components, one of which is a parser.
A common set of components in a compiler is:

• Lexer – break the program up into words.
• Parser – check that the syntax of the sentences are correct.
• Semantic Analysis – check that the sentences make sense.
• Optimizer – edit the sentences for brevity.
• Code generator – output something with equivalent semantic meaning using another vocabulary.

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To add a little bit:

As mentioned elsewhere, small C is a recursive decent compiler that generated code as it parsed. Basically syntactical analysis, semantic analysis, and code generation in one pass. As I recall, it also lexed in the parser.

A long time ago, I wrote a C compiler (actually several: the Introl-C family for microcontrollers) that used recursive descent and did syntax and semantic checking during the parse and produced a tree representation of the program from which code was generated.

Today, I’m working on a compiler that does source -> tokens -> AST -> IR -> code, pretty much as I described above.