Preprocessor

Preprocessor directives are actually the instructions to the compiler itself.

They are operated directly by the compiler.

The most common preprocessor directives are:

• include directive
• define directive

include directive:

The include directive is used to include files.

Example :

    #include <stdio.h>

Here, stdio.h is a header file and the preprocessor replace the above line with the contents of header file.

define directive :

It is used to assign names to different constants or statements which are to be used repeatedly in a program.

These defined values or statement can be used by main or in the user defined functions as well.

Preprocessing directive #define has two forms.

• #define identifier token_string
• Macros with argument

NOTE :

• Preprocessor statements begin with a hash symbol(#).
• Preprocessors are NOT terminated by a semicolon.