Random Number Generator
Nowadays 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 are chosen by a Random Number Generator. The machine's software contains it.
Random numbers are constantly generated by the RNG at an extremely high rate. When a player presses the Play button the most recent random number determines the result. The result varies depending on exactly when the game is played. The result is different every fraction of a second.
The numbers generated by the RNG seem to be not exactly random. The sequence of numbers is repeated by most of the RNGs. The cause of it is in poor programming. Pseudo RNGs with very long periods are relatively easy to build. No computer can 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. The fact that the next set of selected numbers would be based on the previous games played was revealed. 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.

Payout Percentage
Slot machines usually pay out as winnings 82–98 per cent of the money that is wagered by players. This is known as the theoretical payout percentage. The minimum theoretical payout percentage is controlled by jurisdictions. Its establishment refers to the sphere of law or regulation. A certain winning pattern is determined by every casino individually. It concerns 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 is given back to the players.
At the factory when the software is written a slot machine's theoretical payout percentage is set. Changing the payout percentage after a slot machine has been placed on the gaming floor requires a physical swap of the software. As it is a time-consuming process it is done infrequently. In certain jurisdictions the EPROM has a tamper-evident seal. It can only be changed in the presence of Gaming Control Board officials. According to other jurisdictions slot machines are randomly audited 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 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.

Linked Machines
A group of machines offers a particularly large prize, or jackpot if they are linked together in a special way. If a player gets a specific combination of symbols the progressive jackpot from this group of machines is given to him. 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
The reel display of modern slot machines is under computer software's control. It is possible to make the slot machine frequently display combinations that are close to winning combinations.
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. It is winning percentages that control the chance of a winning combination appearing on a pay line. However, the combinations appearing above and below the pay line 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. Only if abbreviated physical reels are used to display a win pattern based upon the RNG this can occur. The symbols that appear around the winning line in video slots are an accurate depiction of how the reels were mathematically modeled.
The issue of a near-miss above or below the pay line was also the subject of the Nevada Gaming Commission investigation. So long as the near-miss above or below the pay line was not specially programmed it was recognized legal. 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 near-miss programming, where a near miss is inaccurately displayed is not allowed either. Due to this, regulators use stop motion cameras to audit manufacturer's practices.

Slots 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. 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.
This type of slots player is the one that believes the win is right around the corner. Just a second and the coins will be flying all over the casino!
The player has either seen a person playing a slots game for a while with no payouts or alternatively they have been depositing funds into a slots game and haven’t yet seen any payouts. They believe that at least any payout is due to happen. They can’t leave the machine because as soon as they do it will burst forth and pay out large sums. Maybe it can really work if you have already spent thousands of dollars and have got nothing back. The machine can’t but paying.
In the old days when a payout occurred players would feel the coins to see if they were hot or cold. If the coins were hot they believed that the machine had not paid for a long period of time. In fact the coins could be hot only because of the numerous lights that heated the coins.
The chaser.
The player believes the slot machine is not one of those machines that never pay. A sense of comfort exists between the slot machine and the player.

Slot machines have a vivid and diverse history. 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.
In fact all slot machines are the same. They only differ in some peculiarities: odds, payouts, payout percentage and symbols. 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 more difficult to understand because you win according to the winning combinations on the paylines, which can be formed in many ways. Sometimes you don't win anything at all, and sometimes multiple combinations award you with relatively big winning money. Paylines can be different. They can be vertical, diagonal, zigzags and what not.
Another interesting variation of the slot machine is a jackpot. If the slot machine has a jackpot it means that a certain amount of each additional bet is added to the jackpot. So the jackpot becomes bigger and bigger with every bet. Jackpots can reach several hundreds of thousands dollars. A certain winning combination hits the jackpot, and the lucky gambler collects everything that the ones before him left behind.
Slot machines are historically played with coins. The new invention is a slot machine online, which doesn’t differ greatly from regular slot machines. Like regular slots they have betting limits, which can be even lower than in real casinos. 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.

It is true that slots are designed to be honest and not to deceive a player. However, in the past certain manufacturers have been caught using computer chips that cheat the customer.
In the old days, slot machines worked mechanically, with independent wheels spinning until they each stopped randomly. Modern slot machines differ form the old ones greatly. Now the integral part of any slot machine is a chip, which is programmed to select numbers randomly. The selected number determines the symbol which then comes out. There is a computer code. It generates the random numbers and determines whether the slot machine is loose or tight. The gaming inspector will examine the machine to make sure it will not deceive the player. There is a legal rate according to which the machine has to pay out. Of course it can pay lower, which happen very seldom.
Because slot machines don’t pay off with every spin, it’s difficult for customers to tell whether a slot machine’s chip has been programmed to pay off less often than is legally required. 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. Once inspectors approve a brand of machine, the manufacturers can make changes to individual machines as long as the changes fall within the legal bounds. Manufacturers can change chips to make a machine pay less as long as the inspectors have approved that particular chip.
In one of the casinos the chip was programmed in such a way that royal flushes would never come out. 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 you’re playing a machine that is not honest, you can complain. In the case if the complaint the inspectors will visir the casino and check whether the machines have a legal chip. Manufacturers that cheat are fined or they can lose their license.

Meet the man who beat the 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. Upon his release, he continued to work on the problem and to devise a better way to cheat the new slot machines. His next invention was a slider, a guitar wire. He inserted it into the machine, which released coins form 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. Tommy found a manufacture who showed him the inside 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. He sold these wands and could earn up to ,000 a day. With all this money he bought expensive cars, houses and what not.
Eventually, all good things come to an end. Tommy was caught using his invention in one of the casinos. While charges from that incident were later dropped, he was caught under similar circumstances in Laughlin and later Atlantic City. By this time, authorities had tapped his phone and recorded conversations with other cheats who used his device. He served three years’ probation and lost both homes. He has been banned from entering any casino.