Introduction to Constants in C++ Programming Language

 Constants in C++

As the name suggests, named constants are variables or values ​​in the C++ programming language that, once defined, cannot be changed. They are fixed values ​​within the program. Any kind of constant can be used, including integers, floats, octal, hexadecimal, and character constants. Each constant has a specific range. Integers too large to fit in an int are taken with the same length. Now there are different ranges from unsigned bits to signed bits.

For Example:

const int num= 25 ;    // num is always 15

num = 25;                    // error: assigning read-only variable 'num'



If it has a low value, it should always be declared as a constant.

const int mintperhour = 60 ;
constant float PI = 3.14 ;



You will Learn following Concepts

• This article explains what C++ constants are and how to define them in C++ with examples . 
• The literals and their types are explained in detail with examples.

C/C++ programs can define constants in two ways:

• Use the #define preprocessor directive.
• Use the const keyword. For example, "const int = 5;" is a constant expression and the value 5 is called a constant integer literal.

Let's take a closer look at the above two methods.

Using the #define preprocessor directive:

This directive is used to declare an alias for an existing variable or any value. Can be used for confirmation
This preprocessor directive provides an alias or reference name for a variable or value. Used to define constants in C++ by giving an alias to the value. This method defines a constant globally.

Syntax:

#define ConstantName Value



ConstantName: 

An identifier for referencing the value in code. Value: The value for which the reference is created.


Using the const keyword:

Characterizing a constant with the const keyword is basically as easy as characterizing a variable, but in practice the definition must be preceded by the const keyword. I have.

Code in C++

#include< iostream >

Using namespace std;

int main( )
{

// int constant in code
const int intNmb = 101  ;

// float constant in code

const float floatNmb = 31.14 ;

// char constant in code
const char charNmb = 'M' ;
// string constant in code
const string stringNmb = "ABZ" ;
cout << "integer constant: " << intNmb << endl ;
cout << "float constant: " << floatNmb << endl ;
cout << "character constant:" << charNmb << endl ;
cout << " string constant: "<< stringNmb << endl ;

return  0 ;
}

Output

integer constant: 101

float constant: 31.14

character constant: M

string constant: ABZ

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