单一指令计算机(英語:one instruction set computer,OISC)也称最简指令集计算机(ultimate reduced instruction set computer,URISC),它是一种抽象计算机,该计算机只有一条指令[1][2][3]。巧妙地选取这一条指令,并且给予无限的资源,单一指令计算机就能成为和其他多指令计算机一样的图灵机[2]:55。在教学上,这种计算机被推荐来帮助理解计算机架构[2]:2[1]:327,同时,也能用它来研究计算机的结构模型[3]。
^ 1.01.1Mavaddat, F.; Parhami, B. URISC: The Ultimate Reduced Instruction Set Computer(PDF). Int'l J. Electrical Engineering Education (Manchester University Press). October 1988, 25 (4): 327–334 [2010-10-04]. (原始内容存档(PDF)于2019-10-18).引文使用过时参数coauthors (帮助)
This paper considers "a machine with a single 3-address instruction as the ultimate in RISC design (URISC)". Without giving a name to the instruction, it describes a SBN OISC and its associated assembly language, emphasising that this is a universal (i.e., Turing-complete) machine whose simplicity makes it ideal for classroom use.