High Quality Content by WIKIPEDIA articles! The Burroughs large systems instruction sets include the set of valid operations for the Burroughs B5000, B5500, and B5700 computers and the set of valid operations for the Burroughs B6500 and later Burroughs large systems including the current (as of 2006) Unisys Clearpath/MCP systems. These unique machines have a distinctive design and instruction set. Each word of data is associated with a type, and the effect of an operation on that word can depend on the type. Further, the machines are stack based to the point that they had no user-addressable registers.