Cardiac – Recreating an educational paper computer from 1968

Photo of assembled CARDIAC


CARDIAC (CARDboard Illustrative Aid to Computation) is a learning aid to understand how a computer operates, created more than 50 years ago by David Hagelbarger and Saul Fingerman for Bell Labs. Building it is easy and can either be done by hand, or with a CNC knife if you have access to one (this saves time and gives an outstanding result).


  • Anyone can build it with just a printer, paper and scissors or a cutting knife!
  • 3 sheets of paper
  • 10 instructions
  • 100 memory cells (using a pencil)
  • High resolution vectorized graphics
  • Original colour scheme
  • Cutting files for CNC knife available
  • Learn how a computer really works and how a program is executed.


I wanted to build a CARDIAC myself but was disappointed in the quality of the black and white scans available. There are high resolution recreated versions, but the ones I found lacked the beautiful aesthetics of the original. Recreating a good looking vectorized version seemed like a great challenge that could hopefully be used by others besides me.

Instead of outlining existing scans I recreated everything from scratch. This allowed me to fit the design on three pieces of A4 or letter paper, while maximizing the computer size (memory and CPU are on separate sheets). If you look closely you will notice that the slides are reversed from the original, since this felt more natural to me. After creating all slides and panels in cad (Rhino3d), I did a few iterations with printed samples. Once everything was working properly, I switched program to Illustrator to finetune the graphics, using similar colours and fonts as the original. I added bleed for the cutting and even spent energy on recreating the ladybug graphic and vectorizing the original ell logo from that time.

The artwork is available in two versions, one with lines for manual cutting and one without lines for CNC cutting. The CNC version has pass-marks to auto align the printed graphics with the cutting path (tested on a silhouette cameo and A4 paper)

Image of page 1 (for manual cutting). Download high resolution PDF below.

Programming the CARDIAC

The original scanned manual explains in a good way how the computer works and describes everything from input devices (punch cards) to output devices (high speed printers). It’s a fascinating read that explains how a computer worked 50 years ago, and even though a lot has changed, the basics of a program is still the same.


To better understand the computer, I wrote a small program that is included in the artwork. Running this program is a good start for all users. Can you figure out what it does?

Before using the cardiac I only had a vague understanding of what bootstrapping a computer really meant. After writing my first program the brilliance of the concept is now clearer than ever (luckily computers don’t get bored…)


Building the computer is very easy, just print, cut and put the slides together. I added numbers to avoid placing them in the wrong order. If you cut it by hand, I recommend that you skip cutting the round holes for the program (sheet 2), since this is a tedious task and you can easily replace moving the bug between holes with moving a small stone or mark current position with a pencil and eraser.

If you build it and appreciate the work, I would be happy if you shared your experience in the comments below. You can also share your programs to allow other to use them

Bill of Materials (BOM)

  • 3x sheets of A4 paper (preferably a bit thicker ~120g/m2)
  • 1x printer (preferably colour laser)
  • 1x cutting knife or 1x computer controlled knife (I used Silhouette Cameo)



This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Leave a Reply