How Are Slot Machines Programmed?

Have you ever asked yourself, “how are slot machines programmed?” Modern slot machines don’t rely on physical reels. Outside of a few vintage games meant for amusement than serious gambling, every slot in a modern casino runs like a computer program. They all use technology like random number generators and algorithms to mimic random results.

Modern slots don’t get physical results. So, lots of people suggest that you can predict the results of the slot machine software. They even claim that you can easily beat the games. If you could predict future results, that would be true.

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Binary code is one way slot machines are programmed
Visualizing how are slot machines programmed

How are slot machines programmed?

This post settles this question in plain language. It discusses how modern slot programmers use technology to produce results that are as random as possible.

Slot Machines & Random Number Generators

Inside every modern slot machine is a microprocessor. It’s much like the one on your laptop or home PC. This microprocessor runs the slot machine game. And it includes a program called a random number generator.

A slot game’s random number generator (RNG) produces a constant string of numbers corresponding to slot machine symbols. A slot’s RNG spits out up to 4 billion numbers every microsecond. These are the virtual stops of a modern slot game.

Every slot machine outcome is the result of a string of numbers produced by this random number generator, following the game’s programming. Slot machine RNGs produce numbers according to the game’s algorithms, complex equations which generate specific strings of randomized numbers.

Programmers code slot machines produce a randomized result, in the interest of fairness. However, that result isn’t entirely random. It sounds complicated because it is.

Slots produce a specific win percentage over time, according to the customer’s order. That means the game’s various series of random results have to work out to a specific win rate for the casino hosting it.

The goal of the game’s programming is to produce that result according to an unpredictable pattern. If the pattern were predictable, the game would be easy for players to exploit. Too much randomness is also undesirable since it would fail to produce the desired win rate for the host casino.

The true randomness of a slot machine is regulated by the organization licensing a particular casino. This is one reason it’s important to play at legit casinos and gambling websites. It would be easy for a bad actor to rip customers off using a shady algorithm or non-random software.

How Are Slot Machines Programmed: Algorithms

In design terms, a game’s algorithms are like its blueprints.

A slot machine’s programming does more than tell the game’s RNG what strings of numbers to produce. It also includes something called an “instruction set” that controls every game function. A game’s expected output is coded into those instructions and operations as well as in the production of random numbers.

Games also include things like the design of animations and music, setting for pay lines, and sets of winning symbol combinations are also defined as part of an algorithm’s instruction set.

To compensate for the lack of a physical process to back the random results of pseudo-RNGs, slot algorithms use something called a seed. This seed value is a random number that then goes through an unpredictable algorithm to trigger a string of results. The idea behind the use of the randomized seed is to replicate forces like entropy, which act on physical processes to produce true randomness.

Most slot pseudo-RNGs use the system clock, already built into the game’s programming, to generate its initial value. Technically, any random and unpredictable number set could be used, but the system clock is already there producing a string of numbers, so it’s practical for game designers to use time and date numbers as a seed source.

The use of these seeds replicates randomness as much as possible in a way that’s still affordable and practical for slot game designers.

Are Slot RNGs Truly Random?

The answer to this question is complicated. It’s important to distinguish between a true RNG and what’s known as a pseudo-RNG.

A true random number generator produces random numbers as a result of some physical process – a dice roll, the variance of radio waves, the physical decay of radioactive elements. Random numbers created by an algorithm, or any other piece of software aren’t considered truly random, since ultimately they’re the result of deterministic choice.

In layman’s terms, pseudo-RNGs are the product of human input, with limitations that prevent them from being truly random.

Designers can replicate the randomness of nature through something called “simulated entropy.” This ties things like the movement of a mouse, user keystrokes, or click rates to create a set of randomized numbers that come close to imitating natural randomness.

Why don’t slot machines use true random number generators? It’s much cheaper and simpler to use a pseudo-RNG than to tie the results of your slot play to the atomic degradation of a supply of Plutonium-244. Plus, I’m pretty sure the federal government would want to have a word with you about your source and containment methods.

It’s impractical for slot programmers to use anything but algorithm-based pseudo-RNGs. Luckily, over the years, computer science has allowed for increasingly-better pseudo-random number generators. Modern video slots have pseudo-RNGs that are indistinguishable from true randomness, at least at the level of the individual slots player.

How Are Modern Slots Regulated?

Randomness is such a major factor in modern slot design that it’s a big part of the way slot games are regulated.

Take the state of Nevada for example. In Nevada, the state government has access to all gaming software, and it’s illegal to use any software not already on file with the state. Gaming inspectors are allowed to show up announced to compare game software with what’s on file with the state. Machines are shut down and operators investigated after a single incident.

Game manufacturers are also subject to inspection and investigation by state and federal gaming authorities. Their employees are subjected to background checks and their criminal records are investigated. All gaming equipment in Nevada is inspected by a public agency that’s in no way connected to the gaming industry.

You could make the argument that slot games are more heavily-regulated than electronic voting equipment or life-saving medical technology. This is necessary to create trust between casinos and their customers.

Make Your Own Pseudo-RNG at Home

Modern pseudo-RNGs are much more powerful than the RNGs of the 80s and 90s. You can fool around with one at home if you have a laptop or computer with Microsoft Excel.

Open a new Excel spreadsheet, select a bunch of cells, and paste “=RAND(  )” into them. Those cells you select will produce a random number between 1 and 0 that goes out to 10 digits. You can highlight all these cells and hit F9 and re-calculate new numbers infinitely.

Believe it or not, this simple tool available to anyone with a Microsoft license or access to a computer with the Excel program is more powerful than the pseudo-RNGs in slot machines just ten or fifteen years ago.

You can use this simple random number generator system to do promotional drawings, call on students randomly and fairly in a class, or choose family members to do chores on a truly random basis.

Think about this another way – if the pseudo-RNG you already have on your laptop is more powerful than the brains of slots just a decade ago, how much more powerful are the random number generation skills of modern slots compared to those older games?

How Are Slot Machines Programmed: Progressive Jackpots

For the most part, machine jackpots and progressive jackpots are programmed the same way.

Consider a Wide-Area Progressive, where machines are linked across multiple casino properties or even from state to state. When a slot machine’s RNG produces the right combination to trigger a progressive jackpot, the information is sent to a centrally-located server, which processes the information from the winning machine.

Progressive jackpots are still based on the randomness generated by an individual slot machine’s programming, but the information is collected and controlled by a server.

How Are Slot Machines Programmed: Conclusion

Part of me wishes modern slots were beatable. Who wouldn’t want to win more at the casino?

I’ve been as frustrated as anyone at the slot machines before, feeling cheated or ripped off – a sure sign that it’s time to end my session. But I’ve also had my fair share of winning sessions, and I realize that the entertainment value of a slot machine lies in its variance. That means I’m likely to see as many losing streaks as winning streaks.

Modern slots produce random results within an acceptable range. Casinos wouldn’t host slot machines that lost money over time. In a sense, all slots are rigged against the player, but that rigging is described in detail in the game’s rules and paytable.

Playing modern slots means playing against modern mathematics and computer science. Don’t fall prey to the idea that slots produce predictable results.

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