C Constants

In this tutorial, you will learn about C constants and how to create them in C Programming.

Constants are the same as variables except they cannot be changed once defined.

C constants are one of the most fundamental and essential parts of the C programming language. Constants in C are the same as variables but the values are fixed, and its value remains the same during the entire execution of the program.

• Constants can be any of the data types.
• Constants are also called literals.
• The best practice in C language is to define constants in upper-case characters.

Defining a C constant

There are two ways to define a constant in the C language.

1. const keyword
2. #define preprocessor

1) Defining C constant using const keyword

Syntax

const type constant_name;

Example

#include<stdio.h> 
int main(){ 
const float PI=3.14; 
printf("The value of PI is: %f",PI); 
return 0; 
}

Program output

Putting const either before or after the data type is possible.

const float PI = 3.14;

or

float const PI = 3.14;

If you try to change the value of PI, it will give the compile-time error.

#include<stdio.h> 
int main(){ 
const float PI=3.14; 
PI=4.5; 
printf("The value of PI is: %f",PI); 
return 0; 
}

Program output

2) Defining C constant using #define preprocessor

The #define preprocessor is also used to define constant. We will learn about the #define preprocessor directive in the later chapter.

Types of C constant