How Slot Machines Work

Gaming technology has evolved rapidly over the past several decades. An article discussing how slot machines work in 2015 is much different than an essay on the subject in 1975. The biggest difference is the change from mechanical-to-electronic gaming machines. The computer chip and random number generator has opened the way for faster and flashier slots with bigger payouts and more gaming features. Today, I want to discuss how electronic slot machines work.

Electronic Reels

When slots had mechanical reels, payouts were constrained by the machine’s limitations. The symbols had to fit on a limited space, so only a certain number of symbols could fit on a reel. Also, the number of reels were limited to three. Slot machines with more than 3 reels had been built, but to accommodate the extra reels, the machines were so large they filled up most of a room, like the computers in a 1950s science fiction movie. This wasn’t feasible for casinos, which had limited space, so the 3-reel machine was standard.

In the age of electronic gaming machines or “EGMs”, everything is done using computer software and hardware. With the results handled on something the size of a pinhead, that creates a world of possibilities. Jackpots can reach vast sizes. Designers can create 5-reel machines, or even the rare 7-reel slot machine. With so much space freed, developers can devote all their time to better graphics, flashier displays, high quality music, and more sound effects.

Also, the game screen has virtual reels, instead a real symbols. That fact means things like the zig zag method of finding the reels starting to line up is not feasible anymore (if it ever was). In fact, no system exists to tell when the jackpot is about to hit.

No Cycle of Payments

One big slots myth is the idea the random number generators on modern slots use a “cycle of payments”. A cycle of payment is a theoretical list of results used to determine the outcome of a spin. The idea of the cycle of payments is the machine cycles through this list to get results, so if a player can determine which part of the list the machine is on, that player can somehow figure out when a jackpot is going to hit.

That isn’t the case. No such list of results exists, because slot machines use true random number generators.

True Random Number Generators

A “true random number generator” is so-named because it truly arrives at the results in a random fashion. You might have found a dice roller or other randomizer online and felt like its results were non-random. Maybe the machine seemed to spit the same number out too often all at once, so that you felt you saw a pattern forming. It’s possible you were correct, because some RNGs on the Internet are not “true” random number generators. They use a big list and, if the list isn’t big enough, you start to notice a pattern.

Random number generators on licensed and regulated slots are totally random. Gaming machines cost thousands-and-thousands of dollars to purchase. These are complicated machines with the ability to generate true randomness, unlike the less involved systems used by programmers online. Thousands of random numbers are generated each second. The very instant the “Spin” button is hit, the last random number spit out is the result you get. For that reason, no cycle of payments exists. You can’t find a pattern in the results. It’s useless to try.

The House Edge

Slot machines work along mathematical principles. Results are not predetermined, but virtually any gaming machine is going to have a house edge. The house edge, sometimes known as the casino’s advantage, deals with expectations and probabilities: in this case, the probability of what the results of the game will be.

If someone plays a slot machine with a 10% house edge, that means they can expect to lose $1 for every $10 you wager or $10 for every $100 wagered. A 5% house edge would mean you would expect to lose $1 for every $20, which converts to $5 for every $100 wagered. Knowing the house edge means you can play your day’s betting by figuring out your bankroll and how much you should bet in order to maintain your bankroll throughout the day.

Again, the house edge does not assure you will lose $5 for every $100; it just means it is probable enough to be expected. Results can vary greatly. Some players win jackpots and walk out the casino doors big winners. Others lose more than expected.

Negative and Positive Expectation

Negative expectation means you expect to lose money. Positive expectation means you expect to win money when you play. Most slot machines won’t have a positive expectation, though progressive slot machines which have a really big jackpot might become positive expectation games. Even then, the expected return is determined by what you would expect to win if you bet as much money as it would take to have a 50/50 expected return–millions of $1 bets. In other words, you would still expect to lose your money, unless your bankroll was several million dollars.

The Truth about Slot Machines

What players should take away from this article is they should start playing a slot machine expecting to lose money. Gambling on the slots is not a way to make money. It is not a way to beat the casino. Playing the slots is a form of entertainment. If you happen to win a big jackpot, know you got lucky and be happy.

Game Features

We talk a lot about slot machine game features on this website. These are nice attractions, but slot machine design begins and ends with the return-to-player or RTP. In many ways, the wild symbols, scatter symbols, free spins, bonus games, and other cool slot machine features are there as a distraction. While it is important to know all the bells and whistles that keep things interesting along the way, it is best to play gaming machines which return the most money to the gambler. This makes for more entertainment.

That’s one reason we cover Bally Technologies slots on this website. While Bally slots are not always the fanciest in terms of presentation and graphics, their slot machines tend to have better odds from a player’s perspective.