Define micro operation and micro code.

A micro operation is a small, basic operation done on data stored in registers in one clock pulse. Examples are shifting a register, adding two registers, or loading one register from another, written as $R1 \leftarrow R2 + R3$.

Microcode is the set of microinstructions stored in the control memory of a microprogrammed control unit. Each microinstruction holds the control signals for some micro operations. A group of microinstructions makes a microprogram, which carries out one machine instruction. Microcode sits between the hardware and the machine language.