The thinking bits of a computer use “flip-flops” to show “up” or
“down” or “ on” or “off”. It’s just as easy to think of these as on/off
light bulbs. Arrays of these flip-flops are used for storing and
manipulating numbers. The point is that they can only have two states
like a light bulb. These two states can also be stores as N/S magnets on
a hard disk, or pits in foil on CD, or high and low voltages in a cable
etc.
