Defination of C preprocessor
The C preprocessor is not part of the comipler, but is a seperate step in compilation process.
- Preprocessor is a program that processes source program before it is passed to the compiler.
- The preprocessor offers several features called preprocessor directives.
- Each of these preprocessor directives begin with a pound symbol(#) symbol.
- The directives can be placed anywhere in a program but are most often placed at the beginning of a program, before the first function definition.
We are going to learn the following preprocessor directives:
Following is a list of all important preprocessor directives:
- #define – Substitutes a preprocessor macro.
- #include – Inserts a particular header from another file.
- #undef – Undefines a preprocessor macro.
- #ifdef – Returns true if this macro is defined.
- #ifndef – Returns true if this macro is not defined.
- #if – Tests if a compiler time condition is true.
- #endif – Ends preprocessor conditional.
Let us understand these features of preprocessor one by one.