A slot is a narrow opening, especially one in a machine or container into which a coin may be inserted to activate the mechanism. The word can also refer to a position in a sequence or series of events (for example, an open time slot on a calendar) or a space in a structure that allows for some type of accommodation (such as the gap between face-off circles on an ice hockey rink).
In computer hardware, a slot is a device that enables expansion cards to plug into the motherboard. A slot can also be found in software, where it is a means of accessing a portion of memory, usually reserved for the operating system or other application programs.
The first slot machine was invented in 1895 by San Francisco mechanic Charles Fey. His invention spawned a huge business for casinos, even though forces of morality and the clergy frequently opposed its operation. By the 1920s laws restricting the sale and transportation of slot machines were in place, although they did not stop the practice entirely.
In the 1980s, electronic components were added to slot machines that allowed manufacturers to assign a different probability to each symbol on each reel. The resulting odds were displayed on the machine’s pay table, and they were often disproportionate to the physical likelihood of each symbol appearing on a particular reel. This allowed a single symbol to occupy several stops on the multiple reels displayed to the player, thereby seeming like it was “so close” to winning.