Teach Your Kids to Code

Chapter 5. Conditions (What If?)

In addition to speed and accuracy, one quality that makes computers powerful is their ability to evaluate information and make small decisions quickly: a thermostat checks the temperature continuously and turns on heating or cooling as soon as the temperature goes below or above a certain number; sensors on new cars react and apply brakes more quickly than we can when another car suddenly stops ahead; spam filters turn away dozens of emails to keep our inboxes clean.

In each of these cases, the computer checks a set of conditions: Is the temperature too cold? Is there something in the path of the car? Does the email look like spam?

In Chapter 4, we saw a statement that uses a condition to make a decision: the while ...