The scan set, also called the scan code set, is a function that converts keyboard key closures to digital signals the computer interprets as alphanumeric characters and special symbols. There are three scan sets in common use. They are called scan set 1, scan set 2, and scan set 3.
In a computer, the scan set is determined by a printed circuit board or integrated circuit (IC) called the keyboard encoder. In order for a keyboard to function properly with a given computer and operating system, the correct scan set, and therefore the correct keyboard encoder, must be used. In keyboards for use with Windows-based computers, scan sets 1 and 2 are the most common.