Manipulating Numbers and Strings
Every program needs to store data temporarily in variables. However, for a program to be useful, it must also manipulate that data somehow to calculate a useful result. A spreadsheet lets you add, subtract, multiply, and divide numbers. A word processor manipulates text to correct your spelling and format text. Even a video game responds to joystick movements to calculate a new position for the player's object such as a cartoon person, airplane, or car. Using data to calculate a new result is the whole purpose of every program.