that allows the clock to be stopped (e.g. a "Stop" button).
* A second control that allows the stopped clock to be manually advanced by one cycle (e.g. An "instruction step" switch and a "Start" button).
* Some means of recording the state of the processor after each cycle (e.g. register and memory displays).

On the IBM System 360 processor range announced in 1964, these facilities were provided by front panel switches, buttons and banks of neon lights. Other systems,