If a transistor is alternatively driven into saturation and cut-off, what does it behave like?

In transistor operation, "saturation" means the device is fully conducting (acting like a closed circuit with minimal resistance), while "cut-off" means it is completely non-conducting (acting like an open circuit). When a transistor is driven back and forth strictly between these two extreme states, it avoids the linear region where proportional changes happen. Instead, this binary on-and-off action makes the transistor behave exactly like a mechanical switch. This switching principle is the core foundation of all digital electronics and computer logic circuits.