C++ Developer -

A constant in C++ is a variable whose value cannot be changed after it is set. You create a constant by adding the keyword const before the type when you declare the variable. Constants are useful for values that should stay the same throughout your program, like the number of days in a week or the value of pi. Using constants makes your code easier to read and prevents accidental changes to important values. This lesson will show you how to create and use constants in C++.

#include <iostream>
using namespace std;

int main() {
    const int DAYS = 7;
    cout << DAYS;
    return 0;
}

• const int DAYS = 7; creates a constant integer with the value 7.
• The keyword const tells C++ that this value must never change.
• The program prints 7.

#include <iostream>
using namespace std;

int main() {
    const double PI = 3.14;
    cout << PI;
    return 0;
}

• const double PI = 3.14; creates a constant decimal value.
• Constants work with any type, including double.
• The program prints 3.14.

#include <iostream>
using namespace std;

int main() {
    const string GREETING = "Hello";
    cout << GREETING;
    return 0;
}

• const string GREETING = "Hello"; creates a constant string.
• Text constants are written in ALL CAPS by convention in C++.
• The program prints Hello.

#include <iostream>
using namespace std;

int main() {
    const int HOURS = 24;
    cout << HOURS * 7;
    return 0;
}

• Constants can be used in calculations just like regular variables.
• const int HOURS = 24; stores the number of hours in a day.
• cout << HOURS * 7; multiplies to find hours in a week.
• The program prints 168.

#include <iostream>
using namespace std;

int main() {
    const int SCORE = 100;
    cout << SCORE;
    return 0;
}

• Constants are perfect for fixed values like a maximum score.
• const int SCORE = 100; sets a value that stays the same.
• The program prints 100.

#include <iostream>
using namespace std;

int main() {
    const int ROWS = 3;
    const int COLS = 4;
    cout << ROWS * COLS;
    return 0;
}

• You can use multiple constants together in an expression.
• const int ROWS = 3; and const int COLS = 4; are two constants.
• ROWS * COLS calculates their product to give 12.
• Using constants makes the meaning of the numbers clear.