The original mechanical slot machine was developed by Charles Fey in the late 19th century. It featured three spinning reels full of symbols and a horizontal center payline that displayed winning (or losing) combinations. Not much changed for almost a century. Even when electronics were introduced, the new models looked very much like their predecessors.
Then computers with Random Number Generators were added in the 1980s and the scene began to change. Today, the variety of slots is mind-boggling and a single casino may feature thousands of machines. Nevertheless, they still fall into a few basic categories, with several variations to distinguish them. Despite innumerable themes and layouts, when a player becomes familiar with one, new introductions in the category are relatively easy to learn and play.
Also called “straight slots” or “spinning reel games,” the classics most closely resemble Fey’s prototype, with side-by-side reels and a central payline. They still make up the majority of machines on slot floors, but the three-reel versions have been joined and gradually replaced by five-reel formats, which allow much bigger payouts for the top jackpot. That’s because matching five symbols is so much more difficult than matching three.
Slots in this category include the standard Single Payline types, such as Red, White & Blue or 777, and the more recent Multiple Payline versions, which offer more than one way to land a winning combination. These are by far the easiest games to understand and play—a good introduction for beginners and a steady source of income for casinos.
Joining these standards are some intriguing variations. Wildcard Slots introduce a symbol that can substitute for any other symbol, giving players more opportunities to win. Multiplier Slots offer a symbol that multiplies the value of a winning combination by 2X, 3X, 5X or even 10X. Bonus Multipliers incorporate the wildcard feature as well.
Progressive slots may look almost identical to the classics, but they have one very big difference—a jackpot that grows and grows until it is claimed. The current amount of the jackpot is displayed on a marquee above the machine, and its value is changing constantly, rolling up higher and higher like the odometer on a car. The total to be won can easily run to seven or eight figures, making instant millionaires out of the winners.
The first progressive jackpot slot was developed in 1986 by International Game Technology (IGT). They called it “Megabucks,” and every progressive game since has been based upon the same principle. Progressive machines are interlinked, not just within a casino but among all casinos featuring the game, in a form of syndication. In order to fund the huge jackpot, a tiny percentage of each bet made on the game goes into a shared prize pool. Even though the amounts that are set aside may be just fractions of a cent, they add up quickly when thousands of machines are involved 24/7.
All a player has to do to claim the grand prize is spin the winning combination on his/her machine. But there is one catch. The progressive jackpot triggers only if Max Bet is played, so anyone going after a fortune should be sure that sufficient credits are loaded to qualify on each and every spin.
The biggest departure from Fey’s invention are “bonus slots” that offer big rewards for combinations that may or may not involve a payline. Many of them award extra spins when certain symbols appear anywhere on the reels. Others have bonus symbols that open a special “bonus game” window where additional credits and prizes may be won.
The bonuses add an extra aspect of anticipation to slot play. What would otherwise be losing combinations turn into opportunities to select treasure chests and find buried gold or to hold reels full of wildcards in position to match up on the next spin.
Almost all of these bonus slot machines use video displays for the bonus rounds, which explains why they were not seen in casino until 1996. That’s when a Chicago-based company called WMS introduced the first one—a fishing themed game known as “Reel ‘Em In.” It led to a huge array of multi-line, multi-coin secondary bonus video games, from Jackpot Party and Filthy Rich to the latest Guns ‘n’ Roses and Family Guy slots.