Wikia

A scomp link was an astromech droid accessory that allowed the droid to plug into computers, via a computer terminal, and other equipment. It consisted of an extensible arm with a rotating tip.

Code cylinders also contained a scomp link that allowed them to interface with security systems and computers.

Scomp link advertisement on the HoloNet News

R2-D2 used this tool to save his masters many times. The first time he saved Padmé Amidala on Geonosis by deactivating a piece of assembly line machinery that would have otherwise killed the Senator. R2 also used his scomp link to control the turbolift Anakin Skywalker and Obi-Wan Kenobi occupied on the Invisible Hand. Later, he used it to stop Garbage Compactor 3263827 from crushing Luke Skywalker, Han Solo, Chewbacca, and Leia Organa on the Death Star. He also used it to open the door to the bay where the Millennium Falcon was located during the escape from Cloud City, and learned that the hyperdrive on the ship had been deactivated. R2 also tried to help using the scomp link during the Battle of Endor at the Endor shield generator bunker. It is, however, believed that not all droids can use these to slice into top secret Imperial files.

Scomp links could also seemingly be used to transmit data from one device to another. While pursuing Rivo Xarran, Boba Fett had the scope on his blaster rifle Scomp-linked to his visor, so he could aim while in a position that would otherwise exclude precision shots.