Small ones are typically a matrix. Each pixel (or element in a simple display like calculator) is connected to a column wire and a row wire, to activate a single pixel you drive the correct pair of wires. For a 6-digit 7-segment display, you would normally have 6 columns (the digits) and 7 rows (the segments) and scan through accordingly. You need to scan the whole display fast enough (100Hz+) that the eye doesn't notice the flicker.
I suggest you do some googling. There are excellent free logic-design courses online that will teach you all of this, including how all the state machines work, etc.
This is not very analogue and I suggest we stop here.