In order to change the brakes on the rear of a Volkswagen you need a computer in order to retract the electronically adjusted calipers. This doesn't answer your question but it does exemplify the current situation. Cars aren't purely mechanical devices anymore. Computers play a large role in their operation.
I find this a bit scary --- mainly because I'm used to cars where the (mechanical) parking brake also can be an emergency brake, and the solid linkage between the lever and the braking mechanism means it is still usable even if all other power is lost. (It's also analog, unlike the "push to set parking brake" on/off behaviour --- especially useful for modulated emergency braking.)
