The RNG
Modern slot machines are computerized. The odds are programmed. The reels and lever are present for historical and entertainment reasons only. A Random Number Generator determines the positions of the reels. It is included into the machine's software.
Random numbers are constantly generated by the RNG at an extremely high rate. When you pres the Play button the result is determined by the most recent random number. The result varies depending on exactly when the game is played. The result changes every fraction of a second.
The RNG was noticed to generate not exactly random numbers. The sequence of numbers is repeated by most of the RNGs. This behavior is due to poor programming. Pseudo RNGs with very long periods canbe built relatively easily. There is no computer that is able to complete a single period in the expected lifetime of the universe. It was Ronald Dale Harris, a former slot machine programmer, who knew the pseudo RNG code and seed values. He discovered equations for specific gambling games like Keno. They allowed to predict that the next set of selected numbers would be based on the previous games played. But the RNG picks numbers even when the machine is not being played. So you can't find an exact place of a number in the sequence.

Percentage Of The Payout
Slot machines usually pay out as winnings 82–98 per cent of the money that is wagered by players. The term theoretical payout percentage is used to denote it. The minimum theoretical payout percentage varies among jurisdictions. Its establishment refers to the sphere of law or regulation. A certain winning pattern is determined by every casino individually. It contains the information about the amounts they pay and the frequencies of these pay-outs. The winning patterns on slot machines are carefully selected to yield a certain fraction of the money played to the house. The rest of the money goes to the players.
At the factory when the software is written a slot machine's theoretical payout percentage is set. Physical swap of the software is needed for changing the payout percentage after a slot machine has been placed on the gaming floor. Being a time-consuming process it is done not very often. In certain jurisdictions the EPROM has a tamper-evident seal. It can only be changed in the presence of Gaming Control Board officials. Other jurisdictions randomly audit slot machines to ensure that they contain only approved software.
Thanks to the newly developed technology the game, the odds, and the payouts would be able to be changed by the casino's slot manager remotely. Only after the selected machine has been idle for at least four minutes can the change be done. After making the change the machine is locked to new players for four minutes, it displays an on-screen message informing potential players that a change is being made.

Linked Machines
Often machines are linked together in a way that allows a group of machines to offer a particularly large prize, or jackpot. A small amount is contributed by each machine in the group to this progressive jackpot which is given to a player who gets a specific combination of symbols. A single slot machine's jackpot is considerably less than the progressive jackpot.
Multiple machines can be sometimes linked across multiple casinos. The machines are then owned by the manufacturer, who is responsible for paying the jackpot.

Near-miss Programming
The reel display of modern slot machines is controlled by computer software. Combinations that are close to winning combinations can be displayed on the slot machine intentionally.
This practice of showing combinations that are similar to winning combinations more frequently than would occur randomly is called near-miss programming.
There is a related phenomenon that is also sometimes 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. This means it is much more likely that a winning combination will appear above or below a pay line than on the pay line. The occurance of this phenomenon is possible when abbreviated physical reels are used to display a win pattern based upon the RNG. The symbols that appear around the winning line in video slots are an accurate depiction of how the reels were mathematically modeled.
The Nevada Gaming Commission investigated the issue of a near-miss above or below the pay line. They ruled that this was legal, so long as the near-miss above or below the pay line was not specially programmed. The near-miss and any other combination should have the same possibility of occurrence. It is impossible to program the machine to show winning combinations more frequently than other combinations above or below the pay line.
In Australia the usage of near-miss programming, where a near miss is inaccurately displayed is also illegal. Due to this, regulators use stop motion cameras to audit manufacturer's practices.

Fraud
Mechanical slot machines and their coin acceptors were sometimes susceptible to cheating devices and other scams.
EPROM computer chips controls modern slot machines and coin acceptors have become obsolete in favor of bill acceptors. These machines and their bill acceptors are designed with advanced anti-cheating and anti-counterfeiting measures and are difficult to defraud. An example of modern ways of slot machine defrauding is directing microwaves toward it to disrupt its proper functioning.

There are at least two types of slot players.
The first type is a persistent player.
These players are sure that the machine is already ready to pay out, they just have to wait for a little. The machine can begin paying in any second.
The player will play until the machine pays out. He must have found a machine that haven’t paid for a long period of time or he has inserted to many coins and has got nothing. They believe that at least any payout is due to happen. 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 will pay any way.
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 were hot they believed that the machine had not paid for a long period of time. But in reality any machine has numerous lights which heat the coins.
The second type of slot players is a chaser.
The player believes the slot machine is not one of those machines that never pay. The player have won and being reinforced by the win gains trust in the slot machine. There is some kind of comfort and trust between the slot machine and the player.

Slots are one of the oldest casino entertainments. They came through a number of changes and improvement. But the objective and the principle of the game always remain the same. Basically, you just put in the coins and wait to find out whether you won or not.
Basically, slot machines are all the same. They have different odds (and of course payouts), different payoffs, different symbols and different exterior arrangement, but there's little difference under the hood. There are so many variatisn of slot machines that everybody can find something to his liking.
The main difference is the number of lines. Slot machines can be either single line or multilane. As it can be understood from its name single line slots have only one line with 4 or 5 wheels. But multi line slots can have up to 25 lines. Multi line slots are a little bit more complicated because winning combinations may play out across a number of lines; when you win, the machine will draw you how the symbols combine together and calculate the win automatically. Sometimes you don't win anything at all, and sometimes multiple combinations award you with relatively big winning money. There are machines with paylines; that is, vertical lines along which a winning combination must occur, but some don’t have them, as the winning combination may come in diagonals, zigzags, strange curves and in other ways and fashions.
Jackpot is also a feature peculiar not for all slots. If the slot machine has a jackpot it means that a certain amount of each additional bet is added to the jackpot. As the players wager, the jackpot grows and grows, sometimes crossing hundreds of thousands of dollars. There is only one winning combination that can bring the gambler the jackpot.
Since slot machines appeared they have been played with coins. The new invention is a slot machine online, which doesn’t differ greatly from regular slot machines. Indeed, as well as with all small wager games, there are top bets - they're known as table limits in table games. Unlike the table games, slot machines don't involve any decision on the player's part and so aren't threatened by game management systems because of their fixed odds; the bet limits are more of a traditional thing than anything else.
Online slot machines also have RNG, which exclude any possibility to cheat. That’s why slots are as fair as it is only possible.

You can be sure that slot machines are designed to be honest. What you can really doubt is the honesty of some manufactures.
When the first slots only appeared cheating was impossible because they worked mechanically, with independent wheels spinning and then stopping randomly. Modern slot machines differ form the old ones greatly. There is a chip inside of every slot machine, this chip is programmed to select numbers randomly. The numbers the computer selects correspond to the symbols that appear on the slot machine’s screen. The computer code that generates the random numbers is responsible for whether the machine is “loose” or “tight,” so gaming inspectors look at the machine’s code to make sure that a slot machine doesn’t cheat. The machine has to pay out either to the legal rate or better. Of course the latter happens very seldom.
It is next to impossible to say whether the chip is programmed not in a right way because the machine is not supposed to pay out with every spin. Before the machines are installed in casinos they are examined by inspectors. But you must understand that inspectors can’t examine every machine. They examine the brands. If inspectors approve the brand, they can produce machines, and change them. But these changes must cover legal requirements. Some dishonest manufactures use the right to produce machines, but use a different chip, which is programmed to pay less or not so often.
There is an example when there was inserted an illegal tip which doesn’t allow royal flushes. Or a chip that shows near misses of a jackpot. One the one hand the machine would never have a jackpot and the player would keep on playing. If you think that you have come across such a machine you have a right to complain. Be sure that inspectors will examine this very machine and the casino itself to make sure everything is ok. Manufacturers that cheat are fined or they can lose their license.

There is a man who managed to cheat slots.
It is not a secret that it is next to impossible to cheat a slot machine. But do you know that Tommy Glenn Carmichael managed to improve the payout of the machine to his benefit.
Tommy is now 53 and he can be said to have spent all his life inventing different devices to cheat slot machines. He was caught with one, called a top-bottom joint, and sentenced to prison. After the release Tommy began to invent new kinds of devices for cheating slot machines. For example, he invented a tool called a slider made from guitar wire that he used to insert into the machine and trip a switch, which released coins from the hopper.
Later the slot machines were not any longer mechanical, they were computerized and as a result there appeared a need for a new device. In some way he managed to fool the manufacture who showed him the inner construction of a slot machine. From that experience, he learned what he needed to know to beat it. Carmichael invented what he called a “light wand. ” The wand, built with a camera battery and a bright miniature light, was used to shine into the slot machine and blind a sensor, causing the hopper to pay out coins. Carmichael marketed these wands to other slot cheats, making as much as ,000 a day. With all this money he bought expensive cars, houses and what not.
But good thing will end one day. For Carmichael, they ended in front of a slot machine at Circus, where he was caught with the light wand when he tried to run from security. He was fined, but soon came back to the same business. By this time, authorities had tapped his phone and recorded conversations with other cheats who used his device. Three years’ probation and expropriation was the punishment. He has been banned from entering any casino.