Comment by kragen

A mechanical power switch can certainly be digital; the Harvard Mark I digital computer was made entirely out of mechanical power switches, actuated by solenoids (so-called "relays"). It depends on how you use it—as you say, by combining multiple different bits, either simultaneously or serially.

I agree that a PWM signal is not really a digital signal, but it's kind of on the edge—for example, https://tinyurl.com/25y54mph is a simulation I designed of a completely analog PWM generator (a simulated LM324 op-amp, five transistors, 13 resistors, and a couple of caps), and several vendors offer better-designed versions of the same thing on an IC, but you can also get a perfectly adequate PWM signal out of a digital GPIO pin, and the PWM peripherals commonly included in microcontrollers are entirely digital.