It is a program that processes our source program before it is passed to the compiler.
Preprocessor command also known as directives.
Each preprocessor directory is begin with a # symbol.
It is can be placed anywhere in the program but are most often placed at the beginning of a program.
The C program is often known as 'Source Code'. The preprocessor works on the source code and creates 'Expanded Source Code'.
If the source code is stored in a file say MYPROG.C, then the expanded source code gets stored in a file MYPROG.I. It is this expanded source code that is sent to the compiler for compilation.
Example of some preprocessor directives as:
- Macro Expansion
- Conditional compilation
- File inclusion
- Miscellaneous directives