In C++, we can define our own constants using the #define preprocessor directive.
#define Identifier value
Example:
#include<iostream.h>
#define PI 3.142
int main ()
{
float radius =5, area;
area = PI * r * r;
cout<<”Area of a Circle = “<<area;
}
Output: Area of a Circle = 78.55
As shown in the above example, once we define a constant using #define directive, we can use it throughout the program and substitute its value.
We can declare constants in C++ using the “const” keyword. This way is similar to that of declaring a variable, but with a const prefix.
Examples of declaring a constant
const int pi = 3.142;
const char c = “sth”;
const zipcode = 411014;
In the above examples, whenever the type of a constant is not specified, the C++ compiler defaults it to an integer type.
