A poker machine simply simulates a physical spinning reel machine.

When you press the button, your bet is taken and the animated reels start to spin. When the reels are spinning the computer is actually deciding what symbols to display. To do this it does a series of things.

To understand what it does we need to know some of the things about the machine.

The Reels

The reels of the machine are actually columns of symbols. You could think of a reel as being a strip of paper with symbols positioned one after the other. The strips for each reel have a different number of symbols and the symbols are in different positions on each reel. The computer numbers the positions on each reel. For example if reel one of a machine has 32 symbols, then the reels strip will be 32 positions long, numbered form 1 to 32. This allows the machine to know which position and therefore, which symbol to display on the screen.