In some cases, you will want to provide constant values that can be used throughout your code. For example, you may decide to declare a constant for π. You should not allow this value to be changed because it will change the underlying logic in your code. This means that you should mark the variable as being constant. When you do this, the compiler will check the use of the variable and if it is used in code that changes the value of the variable the compiler will issue an error:
const double pi = 3.1415; double radius = 5.0; double circumference = 2 * pi * radius;
In this case the symbol pi is declared as being constant, so it cannot change. If you subsequently decide to change the constant, the compiler will issue ...
