C Programming/Constants

There are two simple ways in C to define constants:

1. Using #define preprocessor.
2. Using const keyword.

The #define Preprocessor

//main.c
#include <stdio.h>

#define LENGTH  10
#define WIDTH   5
#define NEWLINE '\n'

int main()
{
   int area;
   area = LENGTH * WIDTH;
   printf("Value of Area : %d", area);
   printf("%c", NEWLINE);
   return 0;
}

The const Keyword

//main.c
#include <stdio.h>

int main()
{
   const int  LENGTH  = 10;
   const int  WIDTH   = 5;
   const char NEWLINE = '\n';
   int area;

   area = LENGTH * WIDTH;
   printf("Value of Area : %d", area);
   printf("%c", NEWLINE);
   return 0;
}