C Constants

C Constants are the identifiers that once defined, cannot be modified. C Constants can either be defined using #define preprocessor or using const keyword. Like C Variables, C Constants name can only be started with a letter or an underscore only.

C #define preprocessor:

Syntax:

#define Constant_name Constant_Value;

• Constant Name: This parameter is used to specify the name of the constant.
• Constant Value: This parameter is used to specify the value of the constant.

C const keyword:

C const keyword is another method to define constants during compilation.

Example 1: Defining C Constants using #define preprocessor

#include <stdio.h> #define AGE 30 void main() { printf ("%d", AGE); }

Output

30

Example 2: Defining C Constants using const keyword

#include <stdio.h> void main() { const int AGE = 30; printf ("%d", AGE); }

Output

30