Constant declaration syntax in C/C++ language

Learn: How to declare a constant in C/C++ programming language? Here you will find constant declaration syntax, explanation and example.

A constant is also the name of memory blocks but we cannot change the value of the constants at anytime (runtime).

Note: Declaration with storage class is discussed in variable declaration syntax in C/C++, we can also use storage class with the constants.

How to declare a constant in C/C++?

const keyword is used to declare a constant in C/C++ language, here is the syntax of constant declaration:

const data_type constant_name = value;

Here,
const is a keyword, which specifies that, constant_name is a constant and we cannot change its value.
data_type is the type of data.
constant_name is the name of constant.
value is the value of constant (while declaring a constant value must be provided).

Example:

//constant integer declaration
const int MAX_ROWS = 100;

//constant float declaration
const float PI = 3.14f;

//constant string (characters array) declaration
const char FLLE_NAME [] = "hello.txt";

Consider the program:

#include <stdio.h>

int main()
{
	//constant integer declaration
	const int MAX_ROWS = 100;
	//constant float declaration
	const float PI = 3.14f;
	//constant string (characters array) declaration
	const char FLLE_NAME [] = "hello.txt";
	
	printf("Value of MAX_ROWS: %d\n",MAX_ROWS);
	printf("Value of PI: %f\n",PI);
	printf("Value of FILE_NAME: %s\n",FLLE_NAME);

	return 0;
}

Output

Value of MAX_ROWS: 100
Value of PI: 3.140000 
Value of FILE_NAME: hello.txt