Components That Make Slot Machines Tick

Random Number Generators in Slots

The RNG is at the heart of a video slot, ensuring that the outcome of each spin is randomly determined. The RNG can generate hundreds of random numbers each second and relies on complex algorithms to do so. It is always working, even when no one is playing the machine.

As long as the slot is plugged in, the RNG continuously produces random whole numbers, usually between 1 and a couple of billion. The computer records the numbers generated at the exact moment the player hits the spin button and feeds them into a program that decides where the virtual reels must stop.

Each spin uses a new RNG output drawn from the full set of possible numbers. The selected numbers are mapped to positions on the virtual reels, telling the game where they must stop. The reels are then set into motion to build suspense, but this is just for show. The outcome of the round is predetermined the moment the player hits the spin button.

The way symbols are mapped on the virtual reels is specific to each game. In some advanced games, pressing the Bet One button, the Maximum Bet button, or pushing the lever causes the algorithm to start at different points.

The use of computer chips has revolutionized slot machines, giving manufacturers and players alike more flexibility. You can now use bills to purchase a predetermined number of credits instead of feeding coins into the machine on every spin. Additionally, both players and gambling operators can easily track how much is won or lost on a given machine.

The Virtual Reels

Modern slots use virtual reels, which allow for a much larger number of possible symbol combinations than games with physical reels do. Mechanical reels must fit inside the slot’s casing, so adding more symbols per reel is possible only up to a certain point.

Casinos need more symbol combinations than mechanical reels can offer if they want to provide slots with odds capable of producing huge jackpots. To achieve this, symbols and spaces are mapped on virtual reels, significantly increasing the number of potential combinations.

Suppose you have a slot with a physical reel that has 10 spaces and 10 symbols: 1 lucky seven, 2 plums, 3 lemons, and 4 cherries. Depending on the manufacturer, identical symbols can be assigned the same or different numbers of stops.

In the example below, identical copies of each symbol are assigned the same number of stops on the reel: 1 for the lucky seven, 3 for each plum, 5 for each lemon, and 7 for each cherry.

A game could also be designed with 4 random numbers for lemon 1 on the first reel, 5 numbers on the second reel, and 6 numbers on the third reel if this produced the desired odds. It all depends on the odds intended for the game.

In slots with mechanical reels, the blank spaces between symbols are also stops. We used only symbols in our example for simplicity. The probability of winning the top-paying combination of three lucky sevens is 1 in 1,000. Consequently, such a game will not yield a huge jackpot even if the designer significantly decreases the payouts for other matching combinations.

When symbols are mapped on virtual reels, the probability of winning with three lucky sevens dramatically decreases to 1 in 125,000.

This enables the game to award top prizes worth thousands of credits while leaving room for more payouts from other matching symbols. Thanks to symbol mapping and virtual reels, slot developers can now create slots with lower variance. This is possible by decreasing the game’s jackpot and increasing the payouts for low-paying winning combinations.

The Payline

The number of paylines is one of the most important features to consider when choosing which slot to play. A payline, or win line, is a pattern of matching symbols on the reels that awards a payout. Paylines can run across the middle of the reels, diagonally, in zig-zag patterns, and so on.

Classic slots with three reels have a limited number of paylines, while advanced video slots feature multiple lines whose number can reach 100 in some games. In slots with five reels, players do not necessarily need to land identical symbols on every reel to win.

Some video slots award payouts for aligning three or even two matching icons on a payline. The more matches you score, the larger the payout you receive. In some games, top-paying symbols award smaller prizes for landing only two identical symbols.

More often than not, the rules require matching symbols to appear starting on the leftmost side and continuing toward the rightmost side of the reels. You normally receive nothing for four cherries on the second, third, fourth, and fifth reels if the symbol is absent from the first reel. Some games have paylines that pay in both directions. You receive a payout when matching symbols align on any active payline.

Playing multi-line slots allows you to win on several paylines during the same spin. The more active paylines there are, the more opportunities you have to collect a prize. However, you must place a bet on a win line to activate it. Otherwise, you will not receive anything even if identical symbols land on that payline.

The number of paylines is fixed in some slots. Players cannot activate or deactivate individual lines and must cover them all with one or more coins on each spin. Suppose you play a game with 20 fixed paylines and can bet between 1 and 5 credits per line. The minimum bet is €0.20 per spin if you play at the first level, betting 1 coin per line with a denomination of €0.01.

In other games, you can adjust the number of paylines played per spin by deactivating some of the available lines. However, winning combinations do not pay when they land on deactivated paylines.

The Paytable

The paytable provides players with important information about the slot they are interested in. It contains all winning combinations of symbols and the number of credits each one pays. Additionally, the paytable lists the bonus features incorporated into the slot and the conditions players must meet to trigger them.

In most cases, the listed coin payouts are based on the first betting level, where you wager one coin per line. You can usually open the paytable by clicking or tapping the info button on the main game screen.

Below is an example from the paytable of NetEnt’s Starburst slot, where you need a minimum of three identical symbols on one of the 10 paylines to win a prize. The game has five betting levels, allowing you to wager up to five coins per active payline. Because paylines cannot be deactivated here, a single spin costs a minimum of €0.10 (€0.01 x 10 paylines).

If you inspect Starburst’s paytable closely, you will notice that some winning combinations do not fully cover the cost of the spin. This is the case with the purple and blue gemstones, which return a minimum payout of 5 credits for 3 matches at the first betting level.

As the image shows, we placed a €0.20 bet of two coins per line (2 coins x €0.01 x 10 lines = €0.20). A combination of 3 blue gems returns 5 credits per coin wagered. Since we scored wins on paylines 1, 3, 5, 7, and 8 at the second betting level, the spin produced a total payout of 5 x €0.05 x 2 coins = €0.50. This example demonstrates how multiple paylines and bet levels work.

Starburst has a more basic paytable than those available in advanced slots. Some games offer higher winning potential, with more paylines, symbols, and winning combinations. Many slots use additional playing card symbols (usually 10, J, Q, K, and A) for their low-paying combinations.

Starburst has only one special feature (up to 3 free re-spins), although some games have multiple features, such as free spins and bonus games. The maximum wager per spin is 100 coins, but this limit can be significantly higher in other slots, where players can risk 400 or even 500 coins.