do-while loop in C++

do-while loop in C++

Its functionality is exactly the same as the while loop except that condition in the do-while is evaluated after the execution of statement instead of before, granting at least one execution of statement even if condition is never fulfilled.

Format:

do statement while (condition);

For example, the following program echoes any number you enter until you enter 0.

// number echoer

#include <iostream.h>

int main ()

{

  unsigned long n;

  do {

    cout << "Enter number (0 to end): ";

    cin >> n;

    cout << "You entered: " << n << "\n";

  } while (n != 0);

  return 0;

}

Output:

Enter number (0 to end): 12345
You entered: 12345
Enter number (0 to end): 160277
You entered: 160277
Enter number (0 to end): 0
You entered: 0

The do-while loop is usually used when the condition that has to determine its end is determined within the loop statement, like in the previous case, where the user input within the block of instructions is what determines the end of the loop. If you never enter the 0 value in the previous example the loop will never end.