Here, I have built what I consider to be the pinnacle of redstone building- a piston memory array. Now, I'm not sure how you will use this, as there are SO many things you can do with this, but here you are.

I would explain how it works, but I'd like to do so with a visual reference, which I do not have.
For experienced redstoners however, I can explain without the reference.
The red wool represents the display and the connection between the pison array and the display.
The blue wool represents the control of the pison array.
The green wool represents the array that advances the NEXT piston array (e.g. 1s digit to 10s digit).
The black wool and the glass is what controls the signals to the red wool redstone, and the purple wool is there just because.

So, what happens when the array cycles (turns) is the redstone within the array attempts to send a signal through the array itself. If there is glass in front of the redstone signal, nothing happens for that part of the display. However, if there is black wool in front of the redstone signal, a current is passed through the array and into the corresponding part of the display.

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Contact me if you have questions, I'll try to answer them as best as I can.

Anyways, I've built it so that you can either push a button to cycle it, or set it up so that it cycles every second.
The entire array will display up to the thousands digit, but I've built it so that you can easily copy/paste the right part to add onto it- if you know what you're copying, that is.