Modern slot machines use microprocessors to assign probabilities to symbols. This allows them to calculate a player’s probability of winning a prize based on what symbols they have matched up on the pay line. The symbols can represent several different things, depending on the theme of the machine. There are also bonus features, which can increase a player’s chances of winning.

The laws regarding slot machines vary from state to state. Some states allow private ownership while others prohibit them. There are no restrictions in Nevada and Arizona, but there are laws restricting slot machines in New Jersey and Mississippi. In Arkansas, however, a slot machine can be privately owned. And in Wisconsin, up to five slot machines are allowed in bars.

The first fully electromechanical slot machine was developed in 1963 by Bally. Its predecessor, the High Hand draw-poker machine, was already electromechanical. In the following year, Bally introduced the Money Honey slot machine, which featured an automatic payout of 500 coins. This machine was highly popular and led to the growing use of electronic games in casinos. The side lever, which had been a mainstay of slot machines before, became almost redundant.

A slot machine’s theoretical payout percentage is set during manufacturing. Changing it requires a physical swap of the software. This software is usually stored in an EPROM, although it may also be stored on a non-volatile random access memory (NVRAM) or CD-ROM. This process is time-consuming, and only authorized Gaming Control Board officials can make the change.