A slot machine (American), fruit machine (British), or poker machine (Australian) is a casino gambling machine with three or more reels which spin when a button is pushed. Slots are also known as one-armed bandits because slot machines were originally operated by a lever on the side of the machine (the one arm) instead of a button on the front panel, and because of their ability to leave the gamer penniless. Many modern machines still have a legacy lever in addition to the button.
Most games have a variety of winning combination of symbols, often posted on the face of the machine (or available on a different screen, accessible by touching a button on the main touchscreen, on video slot machines). If a player matches a combination according to the rules of the game, the slot machine pays the player cash or some other sort of value, such as extra games.
There are many different kinds of gambling slot machines in places such as Las Vegas (as well as casinos modeled after those in Las Vegas, including those operated on Native American reservations). Some of the most popular are the video poker machines, in which players hope to obtain a set of symbols corresponding to a winning poker hand. Depending on the machine, players can play one, 100, or more hands at one time.
Becoming more popular since the 1990's are the multi-line slots. These slots have more than one payline. Reel slots commonly have three or five paylines, while video slots have 9, 15, 25, or as many as 100 different paylines. Most video slots are themed slots, some of which feature graphics and music based on popular entertainers, motion pictures or TV programs (The Addams Family, I Dream of Jeannie, Happy Days, etc.) with a bonus round. Most accept variable amounts of credit to play with 1 to 15 credits per line being typical. The higher the amount bet, the higher the payout will be.
There are also standard 3 - 5 reel electromechanical slot machines, of various types. These are the typical "one-armed bandits". Since about 2005 there have been hybrid machines introduced, which combine elements of both video slots and traditional electromechanical slots.
One of the main differences between video slots and reel slots is in the way payouts are calculated. With reel slots, the only way to win the maximum jackpot is to play the maximum number of coins (usually 3, sometimes 4, or even 5 coins per spin). With video slots, the fixed payout values are multiplied by the number of coins per line that is being bet. In other words: on a reel slot, it is to the player's advantage to play with the maximum number of coins available. On video slots, it is recommended to play as many individual lines as possible, but there is no benefit to the player in betting more than one credit per line with regards to calculating the payout amounts. There are some isolated cases where a video slot machine requires the maximum number of credits per spin to be inserted to win the largest payout, but those are the exception.
As an example, on the "Wheel of Fortune" reel slot, the player must play 3 coins per spin to be eligible to trigger the bonus round and possibly win the jackpot. On the Wheel of Fortune video slot, the chances of triggering the bonus round or winning the maximum jackpot are exactly the same regardless of the number of coins bet on each line.
Larger casinos offer slot machines with denominations from $.01 (penny slots) all the way up to $100.00 or more per credit. Large denomination slot machines are usually cordoned off from the rest of the casino into a "High Limit" area, often with a separate team of hosts to cater to the needs of the high-rollers who play there.
Slot machines common in casinos at this time are more complicated. Most allow players to accept their winnings as credits, which may be "spent" on additional spins.
In the last few years, new slot machines commonly known as "multi-denomination" have been introduced. In a multi-denomination slot machine, the player can choose the value of each credit wagered from a list of options. Based upon the player's selection, the slot machine automatically calculates the number of credits the player receives in exchange for the cash inserted and displays the amount of available credits to the player. For example, a player could choose to wager one dollar per game on a nickel slot machine. This eliminates the need for a player to find a specific denomination of a particular slot machine; they can concentrate on simply finding the machine and setting the denomination once they decide to play.
Recently, some casinos have chosen to take advantage of a concept commonly known as "tokenization," where one token buys more than one credit. A casino can configure slot machines of numerous different denominations to accept the same type of token. For example, all penny, nickel, quarter, and dollar slot machines could be configured to accept dollar tokens. This significantly reduces a casino's inventory costs and coin handling costs. A tokenized slot machine automatically calculates the number of credits the player receives in exchange for the token inserted and displays the amount of available credits to the player. When a player chooses to collect his credits (by pressing a "Cash Out" button), the slot machine will automatically divide the number of credits on the credit meter by the value of one token and return the result to the patron. Any remainder is known as "residual credits" and cannot be collected. Residual credits must be either played or abandoned.
