Microcoding is when the internal control structure of the processor operates in much the same way as the outer machine language program is processed. The micro

Microcoding is when the internal control structure of the processor operates in much the same way as the outer machine language program is processed. The microcode is a sequence of instructions stored in a memory (usually ROM, but can be EPROM or RAM), there is a microcode-program-counter, and the "microcontroller" functions by fetching "microcode instructions" one after another from the memory addressed by the microcode-program-counter. The results of those fetched microcode instructions then control the actual CPU internal hardware elements. And depending on the type of microcode (horizontal or vertical) those microcode instruction's bits either directly control the hardware elements, or get further decoded to then control the hardware elements. A good 10k foot description is "a mini-cpu controlling the hardware - that mini-cpu controlled by the outside visible machine language instructions"