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Next: Example Program: Valid Input
Up: The do-while statement
Previous: The do-while statement
The following loop produces the sum 1+2+3+ ...+n,
where a value for n is entered by the user:
cout << "Enter a value for n: ";
cin >> n;
sum = 0;
i = 1;
do
{
sum += i;
i++;
}
while (i <= n);
Download program.
If the user entered a value of 0 for n then the value of 1
would be returned as the value of sum. This is obviously
incorrect and, as noted above, is because the loop statement of a
do-while loop is always executed at least once. In this case if
the entered value of n is zero then the loop statement should not
be entered at all! Thus if there is any possibility that some valid
data may require that a loop be executed zero times then a
while statement should be used rather than a do-while
statement.