An array processor that was designed by Daniel Slotnick and used a 16-by-16 array of processing units (PUs), each interconnected to its four nearest neighbours. The array of PUs was regulated by a single processor that controlled the flow of instructions to the PUs. The ILLIAC IV was sponsored by ARPA and built by Burroughs Corporation. It became operable at the Ames Research Center of NASA in the early 1970s, and was finally dismantled in 1981.