Micro-operation

In computer central processing units, micro-operations (also known as micro-ops or μops, historically also as micro-actions^[2]) are detailed low-level instructions used in some designs to implement complex machine instructions (sometimes termed macro-instructions in this context).^[3]: 8–9

Usually, micro-operations perform basic operations on data stored in one or more registers, including transferring data between registers or between registers and external buses of the central processing unit (CPU), and performing arithmetic or logical operations on registers. In a typical fetch-decode-execute cycle, each step of a macro-instruction is decomposed during its execution so the CPU determines and steps through a series of micro-operations. The execution of micro-operations is performed under control of the CPU's control unit, which decides on their execution while performing various optimizations such as reordering, fusion and caching.^[1]