One instruction set computer

A One Instruction Set Computer (OISC) is an abstract computer that uses only one instruction (with no need for a machine language opcode). Such computers are the extreme case or the logical conclusion of Reduced instruction set computers, although the concept has been used only in academic circles, as a teaching aid like the URISC.
The Ultimate RISC (URISC) is the name given by researchers at the University of Waterloo in the city of Waterloo, Ontario, Canada, to their implementation of a single-instruction computer. URISC allows complete description of a fully functional computer, in only a few pages.