What is const ?

Const keyword is used in C language to declare a variable constant. It declare a variable as a constant that is the value of the variables does not change during the execution of a program.
We can create a variable as a constant with the help of keyword const at the time of initialization. The value of the constant variable is declared at the time of initialization.

Syntax:

                                const datatype variable_name = value;

It can not be modified.

Ex:

Program: Calculate the area of a circle

      #include<stdio.h>

      #include<conio.h>

      void main()

      {

            const float PI = 3.14; //PI declare as a constant variable

            float area, radius;

            printf(“Enter Radius to calculate the area: “);

            scanf(“%f”,&radius);

            area = PI * radius * radius;

            printf(“Area of Circle = %f”,area);

            getch();   

      }

Output:

      Enter Radius to calculate the area: 5

      Area of Circle = 78.5