Defining Constants

Defining Constants

There are two simple ways in C to define constants:
· Using #define pre-processor
· Using const keyword
The #define Pre-processor
Given below is the form to use #define preprocessor to define a constant:

#define identifier value

The following example explains it in detail:

#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; }

When the above code is compiled and executed, it produces the following result:

value of area : 50

The const Keyword

You can use const prefix to declare constants with a specific type as follows:

const type variable = value;

The following example explains it in detail:

#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; }

When the above code is compiled and executed, it produces the following result:

value of area : 50

Note that it is a good programming practice to define constants in CAPITALS.