Generator Of Random Numbers
Modern slot machines are computerized. So the odds are whatever they are programmed to be. In modern slot machines, the reels and lever exist only for historical and entertainment reasons. The positions of the reels are chosen by a Random Number Generator. The machine's software includes a Random Number Generator.
The RNG generates random numbers at an extremely high rate. When you pres the Play button the result is determined by the most recent random number. The result is different depending on exactly when the game is played. The result changes every fraction of a second.
The numbers generated by the RNG seem to be not exactly random. Most RNGs will repeat their number sequence. This behavior is due to poor programming. 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. Ronald Dale Harris, a former slot machine programmer, was the only one who had access to 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. However, this is impossible for most machines, because 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
Winnings 82–98 per cent of the money that is wagered by players are typically paid out by slot machines. The term theoretical payout percentage is used to denote it. The minimum theoretical payout percentage is controlled by jurisdictions. Law or regulation typically establish it. 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 selection of the slot machines winning patterns is chosen in such a way that it could yield a certain fraction of the money played to the house. The players get the rest of the money.
A slot machine's theoretical payout percentage is set at the factory when the software is written. To change the payout percentage after a slot machine has been placed on the gaming floor a physical swap of the software is required. As it is a time-consuming process it is done infrequently. Certain jurisdictions presuppose the EPROM to have 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.
The technology being developed by the Nevada Gaming Commission would allow the casino's slot manager to change the game, the odds, and the payouts remotely. The change can be done only after the selected machine has been idle for at least four minutes. 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 after the change is 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. 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. A single slot machine's jackpot is considerably less than the progressive jackpot.
There can also be multiple casinos consisting of multiple machines. The machines are then owned by the manufacturer, who is responsible for paying the jackpot.

Near-miss
The reel display of modern slot machines is controlled by computer software. 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 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. However, the combinations appearing above and below the pay line are all roughly equally randomly distributed. There are roughly equally randomly distributed combinations above and below the pay line. This occurs if abbreviated physical reels are used to display a win pattern based upon the RNG. In video slot machines 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. So long as the near-miss above or below the pay line was not specially programmed it was recognized legal. That means that the possibility of near-miss occurrence should be equal to the possibility of any other combination. 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. To audit manufacturer's practices regulators use stop motion cameras.

Slot Machines Fraud
Sometimes mechanical slot machines and their coin acceptors seem to belong to cheating devices and other scams.
Coin acceptors have become obsolete in favor of bill acceptors and modern slot machines are controlled by EPROM computer chips. They are designed with advanced anti-cheating and anti-counterfeiting measures and are difficult to defraud. Nowadays microwaves are used to defraud slot machines.

Here is the list of the most amusing myths concerning slots.
You can spot a winning slot machine.
The only way you'll spot a winning slot machine is when the bells are ringing and the money is dropping. Slot machines use random numbergenerator and that's exactly that. Random.
Casinos place loose slots near the cashier, aisle ways, etc.
If this were true, it would be the only machines anyone would play. A casino mixes slots all over the casino floor. No one with any experience at playing slots would make a statement like this.
Count the number of symbols on the reels to determine your odds.
This is mathematically impossible, remember the RNG (random number generator) determines the stops. Thereare literally millions of combinations on a 3 reel slot machine, so there is no way of determining odds by the symbols on the reels alone.
Casinos can tighten or loosen slot machines from the back office.
It is not as simple as that. The casino can’t just change the chip of the slot machine. It is illegal and it has to be permitted by the commission.
A slot machine that has not been paying is due to hit.
It is not so. With every game the chances of winning are the same.
Pulling the slot machine handle produces more wins than pressing the spin button and visa versa.
Again false. It makes no difference, as the computer only uses these as mechanisms to start the game. Only the computer determines a win or a loss and it has already determined if you are a winner or loser even before the first reel stops spinning.
Playing with hot coins improves your chances.
Once again, the computer determines a win or loss and the temperature of the machine or moneyirrelevant. Although it's funny that people still burn their fingers with lighters believing this works.
Casinos set slot machines to payback more on the weekends.
One more rude mistake. The chances and odds are always the same. It doesn’t matter when you play.