Insert a coin, push a button and see what happens. Electronic slot machines can deliver jackpots to lucky casino players, but odds are slim for any given individual. Seekers of secret strategies tend to be disappointed since the algorithms of the machines are deliberately designed for unpredictable random number generation. The only way to gain a slight edge over others in this form of gambling is to learn how the machines operate and how calculations are generated.

Evolution of Slot Machines

The first slot machine was developed in 1895 by Charles Fey in San Francisco. The following year he opened a factory for manufacturing different types of slot machines, such as the legendary Liberty Bell Slot, the earliest three reel slot machine. The company, however, was wiped out by the 1906 San Francisco earthquake and fire.

But the casino industry lived on. By the 1920s rumors spread that slot machine distribution was controlled by organized crime, leading to laws against them except initially in Nevada. A century later 18 states now allow casino slots.

Original mechanical slot machines used levers, but by the late 1970s electronic slot machines provided buttons, making playing slightly easier. Visual displays became more creative to attract new players.

Basic Slot Operation

A slot machine goes through a process of 8 steps, which are as follows:

1. Coins are deposited in the slot

2. The coins are detected by a coin acceptor

3. Coins go through a payout hopper

4. A sensor detects level of coins in the payout hopper

5. Coins are diverted to a coin counter in a drop box

6. The player pushes a button or pulls a handle

7. The reel mechanism is activated by a shaft

8. A random number generator programs the selected position, causing reels to stop.

The hopper is a motor that spins a metal wheel, which has evenly spaced raised pins on the outer edge of the wheel. The wheel can hold up to a thousand coins, as the number of coins sent to the payout hopper is controlled by the multi-core processing unit (MPU). Once the last coin is delivered to the payout hopper the computer forces the motor to stop.

Reels and Random Numbers

While there are various types of electronic slot machines, many commonly display three or more reels of multiple symbols. Paylines are combinations of symbols you bet on. A major evolution from traditional slots is that physical machines typically use about 20 symbols per reel while modern digital machines have advanced to over 250 symbols per reel. This amount of symbols allows for millions of different combinations.

The core technology and mystique behind electronic slot machines is random number generation. The machines generate thousands of numbers per second that deliver different symbol combinations. The goal is for the results to match the player’s payline. Some machines allow players to bet on multiple paylines per attempt, which is a simple way to slightly increase winning odds.

The amount of payouts comes down to the specific slot machine you choose, paylines and the credits you use for betting. Machines that cost pennies to play usually have more frequent but smaller payouts than more expensive machines. The reason it’s impossible to predict any given play is because each result is independent of previous results. In other words, you can’t learn when a machine is ready to pay just by watching its activity all day.

Why Odds Favor the House

It doesn’t matter which slot machine you play in a casino in terms of affecting odds. No matter which machine you play, odds always favor the house. In other words, it actually is predictable that most of the time you play you’re going to walk away with less money. Odds of winning at card tables are much higher, but the house still always has the advantage.

The reason the odds favor the house is that each casino sets its own parameters on how payouts are determined. Never forget casinos are businesses seeking profits, not playgrounds designed to make everyone rich. The casino’s goal is to receive more than to give money. So part of every casino’s business model is a strategy with built-in edges to ensure profits.

The more a gambler plays, odds increase they will win at some point. The casino, however, controls the odds which are designed to limit chances of frequent winning. So a player might take home profits one night and lose it all over time from continued playing. Although the casino isn’t trying to bankrupt its customers, it knows that keeping people playing longer will increase its profits.

Understanding Probability

It actually takes zero understanding of mathematical probability to win at slots once in awhile, but understanding how probability is measured can provide a clearer view of how slots work. At the foundation of probability science are permutations and combinations. A permutation refers to the action of changing an arrangement of items.

The purpose of probability is to make predictions of events before they occur based on prior history. But the reason gamblers use probability is to calculate potential profits and losses before playing. It can also help you determine how many possible combinations of reel symbols exist on a machine. The equation for figuring out this number is R1 X R2 X R3 as r=reel. Let’s say all three reels have 100 symbols. So the equation to figure out the number of possible outcomes is 100 X 100 X 100, which equals 1 million.

Probability theory includes “the law of averages,” which means the more independent tests of the same experiment are repeated, event results eventually approach theoretical probability. Knowing this concept, casinos program algorithms to work against the law of averages through the use of random number generation.


While it’s impossible to use probability or any other strategy to accurately predict slot machine results, probability can be used to gauge risk management. Slot machines are completely games of chance as winnings are predetermined by computerized random numbers.