C Programming Absolute Beginner's Guide (3rd Edition)

Using do...while

while also can be used in conjunction with the do statement. When used as a pair, the statements
normally are called do...while statements or the do...while loop. The do...while
behaves almost exactly like the while loop. Here is the format of do...while:

Click here to view code image

do

{ block of one or more C statements; }

while (condition)

Note

The do and while act like wrappers around the body of the loop. Again, braces are

required if the body has more than a single statement.

Use a do...while in place of a while only when the body of the loop must execute at least one
time. The condition is located at the bottom of the do...while loop, so C can’t test the
condition until the loop finishes the first time.

Here’s a quick program that uses a do...while loop. It asks the user for two numbers and then
gives the resulting value if the two inputs are multiplied. It then asks the user if he or she would like
to multiply two more numbers. As long as the user keeps typing Y, the program keeps asking for
numbers to multiply. Only answering N breaks the loop.

Click here to view code image

// Example program #2 from Chapter 14 of Absolute Beginner's Guide

// to C, 3rd Edition

// File Chapter14ex2.c

/* This program will multiply two numbers and display the result for

as long as the user wants. Answering 'N' will break the loop. */

#include <stdio.h>

main()

{

float num1, num2, result;

char choice;

do {

printf("Enter your first number to multiply: ");

scanf(" %f", &num1);

printf("Enter your second number to multiply: ");

scanf(" %f", &num2);

result = num1 * num2;