Presumably Duration, Power and Start/Stop. My NEF microwave has a Duration dial, 6 different power buttons (presets for 900, 600, 300, etc) and separate Start and Stop buttons. Oh, and another small button for forcing the Duration dial into a clock setting mode (to set the time-of-day display which is the default when the thing isn't heating).

Works okay, quite intuitive, entirely used to it now.

Just don't get me started on the controls for my induction hob