Do-while Loops

The syntax template for the do-while statement is this:

  do
{
	// statements
} 
while (Boolean_Expression);

The do-while statement is a looping statement. It tests the Boolean expression at the end of the loop. A statement (or a sequence of statements) is executed while an expression is true. The do-while statement differs from the while statement in one major respect: the body of the loop is always executed at least once in the do-while statement.

For example, the following loop reads marks until a valid mark is entered. This do-while loop is event-controlled.

 
do
{
    cout << "Please enter a mark: ";
    cin >> mark;
    if (mark < 0 || mark > 100)
       cout << "Invalid mark. Try again.  " << endl << endl;

}while (mark < 0 || mark > 100);

The following C++ code shows a count-controlled do-while statement:

 
	sum = 0;
	counter = 0;
	do 
	{
       	    cout << "Please enter a mark: ";
	    cin >> mark;
	    sum = sum + mark;
	    counter++;
	} while (counter < 10);

	cout << "The average of the marks entered is " << sum/counter << endl;