Modern Slot Machines-how They Work

This slot machine algorithm works as a random number generator, also known as an RNG. These numbers are constantly generated, and depending on the exact moment you click “spin”, you will get different results. Once you spin the slots, numbers that correspond to positions on the reels are recorded, the reels will then land on those spots. Slot Machine Technology. The main feature of slot games which distinguishes slots from other casino games is, of course, the spinning reels. The reels on slot machines stop on their own or by a player pushing the Stop button (this is the so-called skill stop option), the period of spins and the time of stop are influenced by the RNG which generates random numbers determining the game results.

Introduction

When it comes to gambling, the easier a game is to understand the worse the odds usually are. This is certainly the case with slot machines. Playing them is as easy as pressing a button. However, between the high house edge and fast rate of play, there is no quicker way to lose your money in a casino.

How They Work

Whether you're playing a 3-reel single-line game or a 5-reel 25-line game, the outcome of every bet is ultimately determined by random numbers. The game will choose one random number for each reel, map that number onto a position on the reel, stop the reel in the appointed place, and score whatever the outcome is. In other words, the outcome is predestined the moment you press the button; the rest is just for show. There are no hot and cold cycles; your odds are the same for every spin on a given machine.

Slot machines are just about the only game in the casino where the odds are not quantifiable. In other words, the player doesn't know how the game was designed, so it is difficult to look at an actual game to use as an example. So, to help explain how they work, I created the Atkins Diet slot machine (link). It is a simple, five-reel game with a free spin bonus round, much like IGT's Cleopatra game.

For information on how it works and all the odds, please visit my Atkins Diet par sheet.

For a more complicated example, featuring sticky wilds in the bonus, please try my Vamos a Las Vegas slot machine.

For information on how it works and all the odds, please visit my Vamos a Las Vegas par sheet (PDF).

Odds

The following table shows the casino win for Clark County Nevada (where Las Vegas is) for all slots for calendar year 2012. They define 'slot' as any electronic game, including video poker and video keno. I've found video keno to be about equally as tight as reeled slots, but video poker has a much higher return. So, the return for reeled slots should be higher than these figures.

Clark County Slot Win 2012

Denomination	Casino Win (pct)
$0.01	10.77%
$0.05	5.96%
$0.25	5.74%
$1.00	5.64%
$5.00	5.51%
$25.00	3.97%
$100.00	4.73%
Megabucks	12.89%
Multi-denomination	5.32%
Total	6.58%

Source: Nevada Gaming Control Board, Gaming Revenue Report for December 2012 (PDF, see page 6).

Most players play penny video slots. Based on past research, I find the house edge on those to usually be set from 6% to 15%. In general, the nicer the casino, the tighter the slots.

Advice

While there is no skill to playing slots, there is some skill in selecting which machine to play and ways you can maximize your return. What follows is my advice, if you must play slots at all.

Always use a player card. Slots may be a lousy bet, but the casinos treat slot players very well. A $1 slot player will probably get comped better than a $100 blackjack player. Of course, don't play for the reason of getting comps. You'll give them a lot more than they'll give you.
The simpler the game, the better the odds. The fancy games with big signs and video screens tend to not pay as well as the simple games. However, slot players always tell me the fancy games are more fun.
The higher the denomination, the better the odds. For that reason, it is better to play one coin per line on a 5-cent game than five coins per line on a 1-cent game.
Don't forget to cash out and take your ticket when you leave. It is easy to forget after hitting a jackpot.
Try to play slowly and as little as possible to get your fix.
In some games there is a skill feature, like Top Dollar. In such games, advice is usually offered, which you should take.

Myths and Facts

Just about everything that players believe about slots is untrue. Here are the most common myths and facts.

Myth: Slot machines are programmed to go through a cycle of payoffs. Although the cycle can span thousands of spins, once it reaches the end the outcomes will repeat themselves in exactly the same order as the last cycle.
Fact: This is not true at all. Every spin is random and independent of all past spins.
Myth: Slot machines are programmed to pay off a particular percentage of money bet. Thus, after a jackpot is hit the machine will tighten up to get back in balance. On the other hand, when a jackpot has not been hit for a long time it is overdue and more likely to hit.
Fact: As just mentioned, each spin is independent of all past spins. That means that for a given machine game, the odds are always the same. It makes no difference when the last jackpot was hit or how much the game paid out in the last hour, day, week, or any period of time.
Myth: Machines pay more if a player card is not used.
Fact: The mechanism that determines the outcome of each play does not consider whether a card is used or not. The odds are the same with or without one.
Myth: Using a player card enables the casino to report my winnings to the IRS.
Fact: That makes no difference. If you win $1,200 or more they will report it either way. If you have a net losing year, which you probably will, at least the casino will have evidence of it. Such annual win/loss statements may be used as evidence to declare offsetting loses to jackpot wins.
Myth: The slot department can tighten my game with the press of a button remotely. Thus, you better be nice to the staff and tip them well, or they will use a remote control to have the machine take you down in a hurry.
Fact: There is now some truth to the myth that the odds of a machine can be changed remotely. Such 'server-based slots' are still experimental and in a minority. Even with server-based slots, there are regulations in place to protect the player from the perceived abuses that could accompany them. For example, in Nevada a machine can not be altered remotely unless it has been idle for at least four minutes. Even then, the game will display a notice that it is being serviced during such changes. (source) Meanwhile, for the vast majority of slots, somebody would physically need to open the machine and change a computer chip, known as an EPROM chip, to make any changes.
Myth: The machines by the doors and heavy traffic flow areas tend to be loose while those hidden in quiet corners tend to be tight.
Fact: I've studied the relationship between slot placement and return and found no correlation. Every slot director I've asked about this laughs it off as just another player myth.
Myth: Slots tend to be looser during slow hours on slow days of the week. However, when the casino is busy they tighten them up.
Fact: Nobody would take the trouble to do this, even if he could. The fact of the matter is the casinos are trying to find a good balance between winning some money while letting the player leave happy. That is best achieved by slots loose enough to give the player a sufficiently long 'time on device,' as they call it in the industry, with a reasonable chance of winning so he will return to the same casino next time. If the slots are too tight, the players will sense it and be unlikely to return.
The kind of place you're likely to find tight slots are those with a captive audience, like the Las Vegas airport. So, if the slot manager feels that 92% is the right return for a penny game, for example, he is likely to set every penny game all that way, and keep them that way for years.

Play

Atkins Diet

Analysis

Vamos a Las Vegas

Analysis (PDF).

Australian Reels — One Line

Analysis (PDF)

Australian Reels — Five Line

Analysis

21 Bell

Analysis

Fruit Machine

Analysis

Reviews

Dazzle Me (NetEnt)
Mr. Vegas (Betsoft)
Sparks (NetEnt)

Internal Links

Appendix 1 shows the details and analysis of almost 4000 actual spins on a Reno slot machine.
Appendix 2 shows an example of the virtual reels behind a hypothetical slot machine and how the average return is calculated.
Appendix 3A: 2003 Las Vegas slot machine rankings.
Appendix 3B: 2002 Jean/Primm slot machine rankings.
Appendix 3C: 2002 Tunica slot machine rankings.
Appendix 3D: 2002 Henderson/Lake Mead slot machine rankings.
Appendix 3E: 2002 Quarter and dollar returns for Las Vegas slots
Appendix 4 shows how the return is calculated for my Wizard's Fruit Slot Machine.
Appendix 5 analysis of the 21 Bell Slot Machine.
Appendix 6 Analysis of Red, White, & Blue Slot Machine.
Lock and Roll analysis of the skill-based slot machine found in North Carolina.
Deconstructing Jackpot Party analysis of the video slot machine.
Deconstructing Lion's Share analysis of the classic MGM progressive game.
Deconstructing Megabucks.
Deconstructing the Atkins Diet slot machine.
Analysis of Lucky Larry's Lobstermania.
Deconstructing Hexbreaker.
Deconstructing Blazing Sevens.
Deconstructing Lionfish.
Deconstructing Hot Roll.
Mystery progressives on Ainsworth slots.
Mystery progressives on WMS slots.
Baltimore Sun article, in which I am quoted.
100% Rebate on Slot Losses Promotions: When to quit playing when all losses are refunded.

External Links

For a simplified explanation of slots, please see my companion site Wizard of Vegas
German translation of this page is available at richtigspielen.com
Another decent overview of how slots work and some practical advice for playing them is How Slot Machines Work at VegasClick.com.
PAR Sheets, probabilities, and slot machine play: Implications for problem and non-problem gambling by Kevin A. Harrigan and Mike Dixon, University of Waterloo, Waterloo, Ontario, Canada. This is an outstanding academic paper that details how some popular slot machines were designed.
PAR Sheets, probabilities, and slot machine play: Implications for problem and non-problem gambling - Academic paper based on the par sheets for some modern slot machines

Written by:Michael Shackleford

Most amateur gamblers believe that if a slot machine hits the jackpot, then it immediately goes ‘cold’. They also believe the opposite is true; if a machine runs cold for hours, then it’s ‘due’ for a big payoff. But if you look inside modern slot machines, you learn the cold hard truth. Every single pull of the lever has equal odds of winning, and those odds are steep.

Since the earliest mechanical slot machines, gaming manufacturers have weighted the machines to tweak the odds. If you look closely at the reels of old machines, you’ll find many more blanks and low-scoring symbols than pots of gold, especially on the third or final reel. This creates the famous ‘near miss’ effect.

Modern slots have replaced the gears, cranks and stoppers with precision step motors and random number generators (RNG). When you pull the crank on a modern slot, a built-in RNG selects three numbers between one and 64. Each number corresponds to one of 22 spots on the three reels. The trick is that half of the numbers between one and 64 correspond to blank spots and only one random number matches the jackpot symbol. The odds of nailing the jackpot are 1/64 x 1/64 x 1/64 or one in 262,144.

The lever is just for show. Three internal step motors spin each reel and stop them precisely at the positions chosen by the RNG. Still feeling lucky?

Return vs payback

There is no such thing as a ‘loose’ or ‘tight’ slot machine. In modern casinos, slot machines are programmed to deliver a precise return percentage, somewhere around 95 per cent. That means 95 per cent of the money that goes into a slot machine is paid back out to the players and the casino keeps the rest.
But here’s where things get tricky. The return percentage is not the same as the payback, which is the actual amount of money you win or lose during each gambling session at a slot machine. If you sat down at a slot machine for eternity and pulled the lever an infinite amount of times, your payback percentage would be exactly 95 per cent. Likewise, in a casino full of gamblers, the collective machines will pay back roughly 95 per cent of the total money gambled during the course of a day.

Unfortunately, you are only one person and you don’t have infinite pulls. So your odds of winning are equally good or bad every pull. You could lose all day and that doesn’t mean the machine is rigged. And it doesn’t mean that the guy who wins the jackpot found the ‘loose’ machine. He just got very, very lucky.

Top 5 Facts: Gambling stats

1) Big jackpot, big odds

The odds of winning the jackpot on a ‘progressive’ slot machine like Megabucks is one in 50 million, although if you are that one you’re likely to become very rich.

2) ‘Easy’ money

68 per cent of people who gamble at Las Vegas play the slot machines most often. And there’s a large target market as nearly 90 per cent of visitors to Las Vegas gamble.

3) The house wins

In the United States, gaming was a $92 billion industry in 2007, double what it was a decade ago. And in the UK, there were 143 casinos as of 31 March 2009.

4) United States of Slots

Even though Nevada is widely considered the gambling state, there are 37 US states with some form of legalised electronic gaming device like slot machines or video poker.

5) Vegas’ most wanted

The Nevada Gaming Commission maintains a list of 35 people who are not allowed in any casino or gambling establishment. Only one of them is a woman.