A slot is a narrow opening in something. A slot can be used to hold a coin or other object. It can also be a position in a schedule or program. He slotted the appointment into his calendar. In computing, a slot is one of the positions of a computer motherboard. It is usually designated by a letter such as ISA, PCI, or AGP. See motherboard definition for more information. A slot can also be a position for a device or an attachment, such as a hard disk drive, expansion card, or memory.
Although slot machines have changed a lot over the years, they still work on the same basic principle. When you pull the handle, a series of reels with pictures appear. When a winning combination appears, you win money. The amount you win depends on which symbols line up with the pay line, which runs across the center of a viewing window. Modern slot machines use microprocessors instead of gears to determine what symbols are displayed and which ones have a higher or lower probability of appearing. This allows the manufacturer to make the machine look like it has more combinations, although it reduces the actual number of possible outcomes. It also allows the machine to use a different set of numbers for each reel, so that each visible symbol appears on a smaller fraction of the stops. This is called weighting. Using microprocessors also means that the computer can display more than just the three reels most people expect to see.