A slot machine is a gambling game with spinning reels. Those reels have symbols on them, which land randomly after you place a bet and spin the reels. If these symbols line up, you win prizes based on which symbols fall on that “payline”.
These games have been around since the late 19th century, but they’ve done nothing but grow in popularity since then. They were originally mechanical devices that relied on springs and gears to spin the reels. Modern slot machines use a computer program called a random number generator to determine which symbols land where.
A random number generator is a computer program that cycles through thousands of numbers per second. When you hit the spin button, the program stops wherever it’s at. These numbers correspond to stops and symbols on the reels.
Early Slot Machines
Early slot machines had math that was easily understood. You might have 3 reels with 10 symbols on each of them. The odds of getting any particular symbol were equal—1/10.
If you wanted to calculate the odds of getting a particular combination of symbols on a line, you just multiplied 1/10 X 1/10 X 1/10, for a result of 1/1000.
You could then compare the prize for lining those symbols up with the chances of hitting the combination to figure out the payback percentage for the machine. If a casino offered a 998 to 1 payout on a bet that had a 1/1000 chance of winning, that casino would have a small edge. Over time, they’d show a profit.
Modern slots are harder to calculate, because the symbols and reels are programmed into the computer. This makes the games more flexible in a lot of ways. They’re not limited by the size of the reels, for example.
Vintage mechanical slot machines could only have so many symbols on a reel before the game became literally and physically too large to be practical. But a game that’s powered by a computer might have 20 symbols per reel.
The other advantage for manufacturers is that they can adjust the odds of a particular symbol coming up. Some symbols might turn up once every 10 spins; others might only come up once every 20 or 30 spins. This enables the manufacturers and the casinos to offer larger jackpots and still maintain their profitability.
