In a computer, a jumper is a pair of prongs that are electrical contact points set into the computer motherboard or an adapter card . When you set a jumper, you place a plug on the prongs that completes a contact. In effect, the jumper acts as a switch by closing (or opening) an electrical circuit. Jumpers can be added or removed to change the function or performance of a PC component. A group of jumpers is sometimes called a jumper block .
The plug and play initiative was designed so that users did not have to deal with jumpers. Today, computers come with preset jumpers, although some manufacturers provide jumper settings in the instruction manual so that the owner can reset the jumpers if they want to customize performance.
In electronic test equipment, a jumper cable is used to make a temporary contact between two points for the purpose of testing a circuit.