Its not strictly true ,but for thread purposes my first car was a mid 70's well used Audi 80.
It had a "computer" diagnostic socket!
This was a socket maybe 3 in x 2 in with a flip top cap.
Its effectiveness must have been fairly minimal as everything of any interest on the car was mechanical.
Good sales gimmick maybe
mid 80's to mid 90's any computery stuff seemed to have died off except in connection with mechanical or electronic fuel injection.
Mid 90's basicchips in cars until now,seems you cant scratch your nose without
In comparative terms the computers and os on new cars is still basic compared to general usage.
Its now wrapped up in secrecy and electronic voodoo..individual car owners get left ignorant..there is no self tune, without a lot of research, no more popular car mechanics/move distributor slightly or all that .
For those of us who wanna get bang for buck, its probably why tuning boxes are popular on diesel engines.The nyah nyah effect.
Price of extended guarantees I suppose.
We make it hard for you to stress our products,we extend your guarantee.
I hope it doesnt get too restrictive. In 20 years time(when fossil fuel burners are illegal
See clifford simak's "city". I wanna be able to adjust my electric motor /input voltage just a bit .
"Soylent green is people!"