DIGI-COMP I ("one")  is a mechanical calculation device, delivered in kit form. Originally manufactured from polystyrene parts by E.S.R. Inc starting in 1963, it is as old as I am!
It was sold as an educational toy for just $4.99. Sales passed 100.000 and stopped in the 1970s with the rise of electronic toys.
There are many reference on the web, start with https://en.wikipedia.org/wiki/Digi-Comp_I and E.S.R.


digicomp1 alone total small

DIGICOMP I is quite small: Dimensions are 31 cm x 8 cm x 12 cm. It consists of a mechanical 3 bit memory and programmable logic.

As an "electronic guy", I always was fascinated by mechnical calculation ... powered by a general lack of understanding.  DIGICOMP came into my life after a speach about the arithmetic logic in Zuse Z1 (Klemens Krause on VCFB 2019).

Here it is running here (driven by a self-built motor), programmed to implement a binary counter:


This "binary counter" application as well as detailed functions are found in the user's manual, see attachement.

And: DIGI-COMP I is not to be confused with DIGI-COMP II ... that one is a nice looking marble calculator, but not programmable.


The Original Package

In Xmas 1963, you'd find DIGI-COMP I under your tree in this package (picture stolen from a recent eBay offer):

digicomp1 box

It came as a DIY kit, as a bunch of plastic parts.

digi comp 1 parts 1

You had to assemble all these before use, anticipating our IKEA experiences.

The user manual itself is a retro-futuristic gem and contributes greatly to DIGI-COMPs success.

digi comp 1 instruction 1

Given the age of 1963, the rockets images are not yet inspired by the Saturn V moon-reacher .. .we're still in the Mercury aera here.


In its prime time DIGICOMP had a big community, selected user games and problems were published by E.S.R. in add-on manuals.

Apparently there's still a fan group for DIGI-COMP and similar devices at Yahoo: "FriendsOfDigicomp". I wasn't able to find their message digest, but their file archive is here:

Some interesting documents are attached below.

Modern Implementions

DIGI-COMP is still fascinating people, there are several projects around it. I found these links to be active in 2020:

3D prints

DIGI-COMP I can easily reproduced on 3D printers, because all parts are plastic and flat. For example see this project:


Very important: Thanks to these guys, it's easy to replace a broken 1963 part with own prints. Long life DIGI-COMP!


This is another project for 3D printer, but a modified design:


Minds-On Toys Digi-Comp v2.0

This one is commercial. DIGI-COMP is made from card board instead of plastic.


Check out their site, lots of good info.

Online simulator

This is a web based simulator.


You can develop own logic programs, and save and reload them later.


Of course! http://www.nico71.fr/lego-computer-digicomp/


digi-comp-1-instruction.pdf -- DIGI-COMP I User Manual

digi-comp-1-parts.pdf -- DIGI-COMP I Part List

coding-sheet.pdf -- DIGI-COMP I Coding Sheet as PDF Form

DC1 Detailed Programming.PDF -- DIGI-COMP I Detailed Programming

DC1-PLA.pdf -- DIGI-COMP I as PLA (by friendsofdigicomp)

Duerig.PDF -- DIGI-COMP I Personal Narrative about Invention and Marketing (friendsofdigicomp)

Patent_03273794.pdf -- DIGI-COMP I Patent Original (friendsofdigicomp)

digicomp-romps.pdf -- DIGI-COMP I Game And Problem Book