It was with Gaudi that Otacon controlled the Metal Gear Mk. II and Mk. III, and hacked into other computer terminals via the two mechs. Otacon was also able to connect Gaudi to the damaged Metal Gear REX, via the Mk. III, so that it could be used as the Metal Gear's computer system for Solid Snake's escape from the Shadow Moses facility, and his subsequent battle with Liquid Ocelot's Metal Gear RAY.
Behind the scenes
Gaudi is supposedly the computer that the player accesses when viewing the Metal Gear Solid 4 Database. The name "Gaudi" is taken from the Junker HQ computer terminal in the Japanese version of Hideo Kojima's earlier game Snatcher (which was renamed JORDAN in the English localization of the game). Gaudi also appeared in the 1989 MSX game Nemesis 3: The Eve of Destruction (released shortly after Snatcher), where it was the A.I. computer system installed in Vixen, David Burton's ship. A prototype of the Gaudi appears in Gradius ReBirth, where it has the head of a Metal Gear Mk. II.
Gaudi made an appearance in Konami's 2011 pre-E3 show.