A slot machine is a type of gambling game in which players wager money to win credits. They do so by inserting cash into a slot machine’s coin tray or purchasing paper tickets with barcodes. A lever or button on the machine activates the reels, and when a winning combination is made, the player receives credits in accordance to the paytable. Different types of slots have different symbols, but classic ones generally have fruits, bells, or stylized lucky sevens. Bonus features in slot games are also aligned with the theme.

Most modern slot machines use a computer program to generate random numbers. This random number generator cycles through numbers a hundred times a second, stopping only when the player presses the spin button. The resulting numbers correspond to symbols displayed on the reels, and are known as the “winner”. The first slot machines used math that could be understood by non-experts. For instance, early versions of slot machines had three reels and ten symbols on each. The odds of hitting a winning combination were 1 in ten.

The theoretical payout percentage of slot machines is set at the factory when the software is written. If the player wants to change the theoretical payout percentage, they must physically swap the software. These programs are stored on EPROM chips, but may also be on non-volatile random access memory (NVRAM) or on CD-ROM or DVD. Because this process is time consuming, slot manufacturers have incorporated a tamper-evident seal on the EPROMs. In addition, they are only allowed to perform this procedure in the presence of Gaming Control Board officials.