C++ Demystified(c) A Self-Teaching Guide

Overview

The for loop generally is used when the loop will iterate a fixed number of times. However, sometimes the number of times a loop will iterate is unpredictable, depending on user input during runtime. For example, in a data entry application, you may want a loop that, upon entry of invalid data, asks the user whether they want to retry or quit, and if they want to retry , gives the user another opportunity to enter data. The number of times this loop may iterate is unpredictable, since it will keep repeating until the user either enters valid data or quits.

This chapter will show you how to use the while loop, which is a better choice than a for loop when the number of times a loop will iterate is unpredictable.

While the total number of loop iterations may be unpredictable, there often are situations in which the loop will iterate at least once. An example is a loop that displays a menu with various choices, including exiting the program. In this menu example, the menu always displays at least once; the user cannot choose to exit before being given that choice. In such situations, a do while loop, which this chapter will show you how to use, is a better choice than a while loop.