C Preprocessor

                      Preprocessor directives are actually the instructions to the compiler itself. They are not translated but are operated directly by the compiler. Note that preprocessor statements begin with a #symbol, and are NOT terminated by a semicolon. Traditionally, preprocessor statements are listed at the beginning of the source file.They are also termed as macros.
The most common preprocessor directives are

• include directive
• define directive

1.include directive:
                     The include directive is used to include files like as we include header files in the beginning of the program using #include directive like
#include<stdio.h>
#include<conio.h>
2.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. They are used for
a. defining a constant
b. defining a statement
c. defining a mathematical expression
For example
#define PI 3.141593
#define TRUE 1
#define floatingpointno float
                      Let us take a look at an example to understand how to use preprocessors in C Programming.