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Phillip J. Boucher 


Slot Machine Design


When a manufacture of slot machines begins to engineer a new machine design, a large amount of work goes into research and development in deciding the type of game and theme they should produce. By examining how slot machines are designed, we can get a good understanding as to how they actually work and can see that there is no magic or secret to the operation of a slot machine.


Slot machine manufacturers visit casinos and other gaming venues and talk with executives and employees to get a demographic fit as to what type of customer the gaming industry is looking to cater to, and what types of machines the venue in interested in trying or buying. The manufacturer also talks with customers to find out what they like, what they don't like, and what they would like to see. They tap into other areas of research available to them and get a general idea of what future electronic gaming machine design will be. It's a game of supply and demand. What does the customer want, what do the gaming establishments and regulators want to provide, and what does the maker need to do to satisfy them both?

Market research is extremely important to the creation of a machine that will make money for the operator, and of course money for the manufacturer. This is vital because if a machine is designed that is a flop, a great deal of income is lost and the manufacturer can look forward to less orders from their customers. Casinos also feel the crunch, with players complaining of machines that don't have any appeal for them. This means that when one design fails at one gaming house, the news hits the grapevine and even casinos that have these machines doing well in them find customers slowly avoiding them.


From the initial market research, theme ideas are pitched back and forth between executives, engineers, programmers, mathematicians, and others for months. Everything from graphic design to colors, sounds to music, and even physical shape are debated.

When an initial design is finally agreed upon, development of these machines begins. Themes can be based on movies, books, events, other popular material, or, as in most cases, are created from scratch by a development team. Should we have red sevens or blue sevens? Use this font or that font? How big should the jackpot symbol be? Are we targeting men or women? What age range? What income bracket? Should we go with symbols that represent higher class players such as boats and gold, or should we use traditional fruit and bar symbols to target the lower class players? 

Graphics, colors, shapes, objects, and traditional symbols such as a number 7, cherry, or bar, are all worked out by the team that is trying to come up with a reasonable rendition of what the upper echelon of the company want.


At about the same time as the them design, other members of the team work on the mathematical theory that plays an extremely important roll in the function of slots. Formulas are used to determine payback or hold percentages, odds of winning, symbol assignment, and a plethora of other gaming aspects. For instance, if just one symbol is removed from the reel stop assignment (or an electronic stop position unassigned), or a blank (or ghost) symbol replaces it, this will decrease the payback percentage. If one extra symbol is assigned or an extra ghost removed, this will increase the payback percentage. The actual stop position that these actions are done to are again calculated with several mathematical formulas.

Traditional mechanical reel slot machines usually have twenty-two physical positions on them; eleven blanks, or "ghosts", and eleven symbols. The actual physical number of possible combinations is 22 times 22 times 22, or 10,648 different combinations. With the jackpot represented by only one set of symbols, the odds of hitting it are 10,648 to 1. Now, you would think these odds are pretty low, right? Well they are, but to create a program that will make money and comply with the minimum payback percentage each jurisdiction requires, multiple electronic positions, or "stops", are programmed for the game. (Video slots are similarly designed, except the "physical" stops are virtual as well.) So stop number 1, which is usually three ghosts, may have one or more virtual stop positions assigned to it, such as 13, 34, 56, 145, 167, etc. This is done for each physical position on each reel. There may be 200,000 or more electronic stop positions programmed for a game. Now the odds become even less enticing. 200,000 to 1 odds of hitting the jackpot now means that not only is it harder to hit the big one, but the casino will make more money over the long term because of the increase in non-winning combinations.

One thing that most people don't know is that a manufacturer may have only five or six different game programs, but will create various themes for each one. As an example, a three reel game theme of Double Tomatoes may have the graphics of tomato products on the machine and reels. Three Double Tomatoes gets you the jackpot. Then the manufacturer may simply change the theme to a Lucky Ticket theme. The graphics for tomato products are simply replaced by graphics representing lottery tickets. Three Lucky Tickets gets you the jackpot. Two totally different themes targeting different types of players, yet only one program need be designed. The player however, thinks they are two totally different games altogether.


The gaming and reel chips or cards are programmed by the manufacturer for each game theme and percentage. These chips or cards are then sent to the regulating body of the jurisdiction that the manufacturer would like to market their new game in. In most jurisdictions, the chips or cards are sent to a forensic laboratory in which they undergo a so-called "electronic autopsy".

This electronic autopsy involves ensuring that the game program strictly adheres to all the rules and regulations that the regulating jurisdiction has implemented. If the program passes the exam, an electronic copy is made and the manufacturer gets the go-ahead to sell their new game. The regulating jurisdiction then makes this electronic copy available to all the electronic enforcement personnel to be placed on their desktop and laptop computers.


Every jurisdiction has their own way of verifying the game programs, so this method is a very generic version. Once the manufacturer gets the go-ahead, they sell their new machines to casinos. They supply the cabinet and all the guts and graphics, peripheral equipment such as handles, reel strips, and hoppers, and copies of the machine program on chips or cards.

Once the games are installed on the gaming floor, the CPU's are set out for the electronic gaming officers. The officers verify each chip or card with the approved programs stored in their computers. If the chips or cards pass, they are installed on the CPU and are sealed with government tape. At this point nobody can change anything about the machine's programming without breaking or damaging the seal. If the seal is discovered broken or damaged in any way other than being broken officially by a gaming officer, the machine is shut down and sealed, and an investigation commences in conjunction with law enforcement personnel, with extremely severe penalties waiting for anyone who may have tried to remove the seal deliberately or failed to report finding it broken or damaged.

In some jurisdictions it may the techs who place the seals on the cards/chips, or no seal may be used, and the gaming inspectors simply do random spot checks. Regardless, legalized gaming across the planet is done with honesty and integrity. If you are concerned about how your own jurisdiction regulates gaming, visit their website or give them a call.

Entire contents 1998 - 2018  Phillip J. Boucher

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