2. Compilation and macroexpansion

The C language is mainly implemented by compilation, although there are a few C interpreters such as EiC. The file is the compilation unit. The compiler works in several passes. The very first are very simple, such as the elimination of backslashes at the end of a line, followed by the elimination of comments (which start with /* and end with */ ).

The first really important pass corresponds to a macroexpander called cpp (C pre-processor ). In fact, a file destined for a C compiler is a mixture of two different languages, i.e. a C background structured by macroexpansion directives. The result of the macroexpansion is pure C that will be compiled.

Thecpp macroexpander is a modest but general-purpose tool that can be used independently of C to process any type of text.