Constants in C language

Constants are such entity in program whose value remain same during the entire execution of the program after being set. They are also called Literals.

• Constants can be any of the data types like integer constant, floating constant, char or string constant.
• Programmer use upper case naming convention to define constants as a best practice.

Syntax

const type constant_name = value;

const keyword is used to define constant in C.

Example

#include<stdio.h>

int main()
{
  const float PI = 3.14;
  const int RADIUS = 5;
  float area;
  area = PI * RADIUS * RADIUS;

  printf("The area of the circle with radius: %d is: %f sq. units.\n", RADIUS, area);

  return 0;
}

# output
The area of the circle with radius: 5 is: 78.500000 sq. units.

We have two constants in above program:

• RADIUS: An integer constant
• PI: A float constant

Constant Types in C

Using #define

We can also define constant using preprocessor.

The syntax is:

#define constant_name value;

Example: #define PI 3.14