Static variables

The static keyword can be placed before the datatype in a variable declaration to create a static variable. Static variables adhere to three rules:

• They are initialized only the first time the declaration is encountered in the program
• They remain in memory after the scope of the variable ends
• Despite remaining in memory, they are still only accessible within the scope of the variable

One use of a static variable is to count the number of times a function has been called as shown below:

void fcn()
{
     static int i = 0;

     cout << "This function has been called " << ++i << " times." << endl;
}

fcn();     // This function has been called 1 times.
fcn();     // This function has been called 2 times.
fcn();     // This function has been called 3 times.
fcn();     // This function has been called 4 times.
fcn();     // This function has been called 5 times.

The static keyword has other uses in C++, especially related to classes.