You should check out:
- Core memory - Drum memory - Bubble memory - Mercury delay line memory - Magnetic type memory :P
And probably many more. Remember that computers don't even need to be digital!
> computers don't even need to be digital!
or electric.
This stores a whole scanline https://www.youtube.com/watch?v=bsk4WWtRx6M. This or something similar was in almost any decent color TV except for the oldest.