You can write any program in C language without the help of enumerations but, enumerations helps in writing clear codes and simplify programming.
C Programming Preprocessor and Macros
Preprocessor extends the power of C programming language. Line that begin with # are called preprocessing directives.
Use of #include
Let us consider very common preprocessing directive as below:
#include <stdio.h>
Here, "stdio.h" is a header file and the preprocessor replace the above line with the contents of header file.
Use of #define
Preprocessing directive #define has two forms. The first form is:
#define identifier token_string
token_string part is optional but, are used almost every time in program.
Example of #define
#define c 299792458 /*speed of light in m/s */
The token string in above line 2299792458 is replaced in every occurance of symbolic constant c.
C Program to find area of a cricle. [Area of circle=πr2]
#include <stdio.h>
#define PI 3.1415
int main(){
int radius;
float area;
printf("Enter the radius: ");
scanf("%d",&radius);
area=PI*radius*radius;
printf("Area=%.2f",area);
return 0;
}