The ‘C’ Preprocessor

The ‘C’ Preprocessor


Before a C program is being executed, there are several prior steps involved. One of them is Preprocessing. The Preprocessor is the program that processes our source program before it is available to the compiler. The preprocessor offers several features known as preprocessor directives. They direct the compiler in various ways.

A directive starts with a # symbol and guides the compiler to behave in a special way. The directives are usually placed at the beginning of a program before the main() function, though it can be placed anywhere before a beginning of a function.

Preprocessing involves the directives

a) Macro expansion
b) File inclusions
c) Conditional compilation