Generator Of Random Numbers
Modern slot machines are computerized. The odds are programmed. The reels and lever are present for historical and entertainment reasons only. The positions of the reels depend on a Random Number Generator. It is included into the machine's software.
The rate of generating random numbers by the RNG is extremely high. As soon as the Play button is pressed, the most recent random number is used to determine the result. That means that the result depends on exactly when the game is played. The result changes every fraction of a second.
Some professional gamblers observe that the RNG does not actually generate random numbers. Most RNGs will repeat their number sequence. Poor programming determines such behavior. To build pseudo RNGs with very long periods is relatively easy. A single period can't be completed by any computer in the expected lifetime of the universe. The access to the pseudo RNG code and seed values was known to Ronald Dale Harris, a former slot machine programmer. Equations for specific gambling games like Keno were discovered by him. Thanks to them the fact that the next set of selected numbers would be based on the previous games became known. But it is impossible for most machines, because numbers are picked by the RNG even when no one plays. So the player cannot tell where in the sequence they are.

Payout Percentage
Slot machines usually pay out as winnings 82–98 per cent of the money that is wagered by players. This payout percentage is called theoretical. Jurisdictions serve to control the minimum theoretical payout percentage. Law or regulation typically establish it. Nearly each casino has its own winning pattern. The amounts they pay and the frequencies of these pay-outs are reflected in it. The main criterion for selecting the winning patterns on slot machines is that they should yield a certain fraction of the money played to the house. As for the rest of the money it goes to the players.
When a slot machine's software is written its theoretical payout percentage is also set. To change the payout percentage after a slot machine has been placed on the gaming floor a physical swap of the software is required. Based on current technology, this is a time-consuming process and as such is done infrequently. Certain jurisdictions presuppose the EPROM to have a tamper-evident seal. To change it Gaming Control Board officials should be present. Other jurisdictions constantly ensure that slot machines contain only approved software.
The Nevada Gaming Commission is working now with Las Vegas casinos on technology that would allow the casino's slot manager to change the game, the odds, and the payouts remotely. The change cannot be done instantaneously, but only after the selected machine has been idle for at least four minutes. After the change is made, the machine must be locked to new players for four minutes and display an on-screen message informing potential players that a change is being made.

Machines Linking
Often machines are linked together in a way that allows a group of machines to offer a particularly large prize, or jackpot. Each slot machine in the group contributes a small amount to this progressive jackpot, awarded to a player who gets a specific combination of symbols. The amount of the progressive jackpot is far higher than any single slot machine's.
Multiple machines can be sometimes linked across multiple casinos. In these cases, the machines may be owned by the manufacturer, who is responsible for paying the jackpot.

Near-miss Programming
Computer software controls the reel display of modern slot machines. That is why it is possible to make the slot machine frequently display combinations that are close to winning combinations.
The term near-miss programming is used to denote this practice.
There is a related phenomenon which is also called near-miss. The chance of a winning combination appearing on a pay line is controlled by the winning percentages programmed into the slot machine. The combinations above and below the payline are all roughly equally randomly distributed. There are roughly equally randomly distributed combinations above and below the pay line. This phenomenon only occurs where abbreviated physical reels are used to display a win pattern based upon the RNG. Video slot machines have virtual reels and the symbols that appear around the winning line are usually an accurate depiction of how the reels were mathematically modeled.
The issue of a near-miss above or below the pay line was also investigated by the Nevada Gaming Commission. If the near-miss above or below the pay line was not specially programmed it was stated to be legal. That means that the possibility of near-miss occurrence should be equal to the possibility of any other combination. The machine cannot be specially programmed to show winning combinations more frequently than other combinations above or below the pay line.
Australia also forbids to use near-miss programming, where a near miss is inaccurately displayed. Manufacturer's practices are audited by regulators with the help of stop motion cameras.

Slot Machines Fraud
Mechanical slot machines and their coin acceptors were sometimes susceptible to cheating devices and other scams.
Modern slot machines are controlled by EPROM computer chips and coin acceptors were changed for bill acceptors. These machines and their bill acceptors are designed with advanced anti-cheating and anti-counterfeiting measures and are difficult to defraud. Recent attempts at defrauding slot machines involve manipulating the EPROM, such as by directing microwaves toward it to disrupt its proper functioning.

As you know there are different types of slot machines. And do you know that there are even types of slot palyers.
The first type is a persistent player.
The players of this type believe that very soon there will be a period when the machine begins to pay. The machine can begin paying in any second.
Players become so persistent if they have already spent a lot of money for this slot and haven’t got anything or if they have found a slot machine that haven’t paid for a long period of time. They know the next big win, or any win is due to pay out. The rush is that if they leave after depositing so much money in the machine it will erupt and the payouts will be often and large. Maybe it can really work if you have already spent thousands of dollars and have got nothing back. The machine can’t but paying.
Many years ago players have their own way of determining whether the machine has not paid out for a long period of time. They touch the coins to see whether they were cold or hot. If the coins where hot then the slot machine had not paid out in a while and to the chaser this was good as the machine was do. The heat of the machines lights, etc would eventually heat the coins.
The chaser.
The player thinks that the machine he is going to play is not a machine that never pays. Players feel more comfortable and confident because they have been reinforced with a win and gain trust in the machine. There is some kind of comfort and trust between the slot machine and the player.