Most slot machines have three or five reels and multiple symbols on them. When a player presses the button or pulls the handle, the machine’s random number generator picks a number and signals the reels to stop at that spot.

This process operates continuously, picking hundreds of numbers per second. This prevents players from being able to predict a winning combination.

Random number generators

The random number generator (RNG) is a microprocessor in the slot machine that selects a sequence of numbers randomly. It’s the heart of the machine and determines if you will win or lose. It isn’t affected by how much you have won or lost in the past, just like a coin flip is not influenced by previous heads or tails.

It is constantly working, selecting a random set of numbers every millisecond and mapping those numbers to the possible positions on the reels. This process is the reason why a spin of a slot machine is always different from any other spin.

While the RNG is the god in the machine, it’s not as mysterious as some people might think. It’s just a computer algorithm that does a very specific job and behaves a lot like it would if there was nothing else to do. The reality is that there is no other way to make a machine generate random numbers.


In the old mechanical days, slot machines used reels that spun to produce combinations of symbols. If a symbol lined up with the pay line, the machine would dispense coins or, in “ticket-in, ticket-out” machines, paper tickets with barcodes. Modern slots use a different system. A central computer controls the outcome of each spin, using a random number generator to determine where the symbols should stop. These systems can use physical or video reels, and they can vary in size and shape.

The odds of getting a jackpot symbol on a particular virtual reel are based on the weightings assigned to each of its stops. These are detailed in a par sheet, which gives the house edge of each machine. The weightings increase from the front of a reel to the back, making it less likely that a high-paying symbol will appear on the first reel. This is known as a near-miss effect. Video reels, however, don’t have the same issue.


Symbols are cultural representations of reality that may take on different meanings over time. They can be as small as an icon that stands in for a specific word, or they can be as large as an entire nation’s political system. Symbols are also a key element in any story, allowing readers to quickly understand the deeper meaning behind an image or gesture.

Modern slot machines have microprocessors that assign a probability to each possible combination of symbols. This information is recorded on a database and used by the machine to select a reel for each spin. Some symbols are wild, substituting for any other symbol to form a winning line. Others are stacked across multiple reels and can create more than one winning combination.

Many people believe that a slot machine is “due” to pay out when it has gone long without hitting, but this belief is often based on misconceptions about probability and how the machines work. A more accurate way to view a slot’s odds is to look at the pay table, which lists the potential amounts of payouts for each symbol.


Since microprocessors replaced electromechanical switches in modern slot machines, manufacturers have more freedom to vary payout values. They can even assign different probabilities to each symbol on a given reel. This allows them to produce near-misses, which can make the machine seem “hot” or “cold.”

The odds of a particular symbol are determined by the par sheet, which specifies the weightings for each stop on a given reel. However, gambling companies keep the par sheets secret, so players never get a clear picture of the odds or house edge.

Despite popular belief, slot machines don’t get hot or cold. Every spin is independent of the previous and following ones, and the random number generator can select any combination of symbols. This is why it can feel like a slot machine is “hot” after two consecutive wins, then goes cold for ages before suddenly returning to life. It’s a mathematical illusion.