Constants in CPP (C Plus Plus)

WHAT are CONSTANTS?

The difference between variables and constants is that variables can change their value at any time but constants can never change their value.

Tips for Constant variable

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

There are two methods for a constant variable in C++

1. By using the const keyword

Syntax:
const type constant_name;

Example with the const keyword

#include <iostream>
using namespace std;
int main()
{
  const float e = 3.1415; //constant variable
  cout<<"value="<<(e*10);
  return 0;
}

#include <iostream>

using namespace std;

int main()

{

const float e = 3.1415; //constant variable

cout<<"value="<<(e*10);

return 0;

}

2. By using #define Preprocessor keyword

Syntax:
#define constant_name;

Example with #define keyword

#include <iostream>
using namespace std;
#define e 3.1415; //constant variable
int main()
{
  cout<<"value="<<(e*10);
  return 0;

}

#include <iostream>

using namespace std;

#define e 3.1415; //constant variable

int main()

{

cout<<"value="<<(e*10);

return 0;

}