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Before the do loop begins, I declare the character again. However, I don’t need to initialize it because it’s not tested until after the first iteration of the loop. I get a
58 Chapter 2 n Truth, Branching, and the Game Loop: Guess My Number
new value for again from the user in the loop body. Then I test again in the loop expression. If again is equal to ’y’, the loop repeats; otherwise, the loop ends.
IR W
Even though you can use while and do loops pretty interchangeably, most programmers use the while loop. Although a do loop might seem more natural in some cases, the advantage of a while loop is that its expression appears right at the top of the loop; you don’t have to go hunting to the bottom of the loop to find it.
If you’ve ever had a game get stuck in the same endless cycle, you might have experienced an
infinite loop—a loop without end. Here’s a simple example of an infinite loop:
int test = 10; while (test == 10)
{
cout << test;
}
In this case, the loop is entered because test is 10. But because test never changes, the loop will never stop. As a result, the user will have to kill the running program to end it. The moral of this story? Make sure that the expression of a loop can eventually become false or that there’s another way for the loop to end, such as described in the following section, “Using break and continue Statements.”
