C++ Constants

Declaration & Assignments

C++ Constants

Constants are like variable, except that their value never changes during the program execution once defined

What are Constants?

Constants refer to as fixed values, unlike variables whose value can be altered, constants – as the name implies does not change, they remain constant. Constant must have to be initialized at the time of creating it and new values cannot be assigned later to it.

• Constants are also called literals.
• Constants can be any of the data type.
• It is considered best practice to define constants using only upper-case names.

Constant Definition in C++

There are two other different ways to define constants in C++. These are:

• By using const keyword
• By using #define preprocessor

Constant Definition by Using const Keyword

Syntax:

const type constant_name;

Example:

#include <iostream>
using namespace std;

int main()
{
  const int SIDE = 50;
  int area;
  area = SIDE*SIDE;
  cout<<"The area of the square with side: " << SIDE <<" is: " << area << endl;
  system("PAUSE");
  return 0;
}Run 

Program Output:

It is also possible to put const either before or after the type.

int const SIDE = 50;

or

const int SIDE = 50;

Constant Definition by Using #define preprocessor

Syntax:

#define constant_name;

Example:

#include <iostream>
using namespace std;

#define VAL1 20   
#define VAL2  6
#define Newline '\n'

int main()
{
   int tot; 
   tot = VAL1 * VAL2;
   cout << tot;
   cout << Newline;
}

---