 In the preceding videos, we had to either do input before the loop and at the bottom of the loop or set a boolean to tell whether the loop was done. We had to do this because the while loop checks for the condition before doing the loop body. If the initial test of the condition comes back false, the loop body never happens at all. But when we're doing input, we have to ask for input at least once. To handle the case when you want to go through a loop at least once, C provides the do while loop, whose flowchart looks like this. The loop body happens first, and then the condition gets tested. You are guaranteed at least one trip through the loop. Here's how you write it in C. You must follow the condition with a semicolon to end the do while statement. And here's the code for the age program. We start the do while loop, prompt for the input and read it in. If the input is not equal to zero, we calculate and print the number of years and days. And we do the body of the loop as long as years isn't zero. Let's build and run this to see that it works, and it does. In summary, a while loop tests the condition first. If it's false, the loop body won't be executed at all. Do while test the condition last. The loop body will be executed at least once.