In the previous chapters, we printed some expressions. However, what to do if we need to store these expressions for future usage? In C++ (like in other programming languages) there are containers to keep data - variables. For each type of data (numbers, strings, characters) there is a type of variable.

Let’s take a look at the most often used types:

 const double x = 42;

The variable x will always be 42 and nobody can change it. The following code would cause an error:

 const int x = 10;
 x = 15;

You should declare variables as constants if you are sure that they will probably never change:

 const int monthPerYear = 12;
const char firstAlphabetLetter = 'A';