Every program needs to give the user a way to control the computer. In the old days, that meant knowing how to type the proper commands to make a program work, but with today's graphical user interfaces, the easier way to control a program is to choose from a list of available commands. The simplest way to give a command to a program is through a button.
By displaying multiple buttons on the screen, a user interface offers multiple choices for the user at all times. Instead of memorizing cryptic commands, the user just needs to select a command by pointing at it with ...
