Book Review: How to Build a Working Digital Computer

From: Dave Dameron <>
Date: Tue Mar 2 18:29:55 1999

At 04:49 PM 3/2/99 -0500, you wrote:
>I think somebody may have mentioned this book before, but I just picked up
>a copy yesterday. Cool! It was written in 1968, and has a picture of a
>bunch of bent paperclips on the cover. What the? It goes into details of
>building all the elements of a computer, even core memory, out of
>Find this book! Buy it! Has anybody built the stuff from the book?
It was me for one who mentioned it before. There must have several
editions, as my notes say 1964 (or I made another mistake). It made very
liberal use of double pole double throw knife switches, like those still
available today at Radio Shack.

For example, the binary to decimal converter used 4 (gangs) of switches to
power 10 lamps. The first gang, a single pole switched between 0-7 and 8-9.
You get the picture for the other 3 gangs.

The drum was a metal can with contacts to 20 or so flashlight lamps.
Segments of the drum were covered up with tape so various lamps were lit as
one rotated the drum. The lamps were instructions for you to switch the
various knife switches, you rotated the drum to see the steps to take.

The switch logic for a 1 bit adder was very interesting. 4 were used. The
addend and augend (Been a few years since I used those words!) input were
switch positions, but the carry (true and comp.) inputs were generated from
the lower bit switches. The sum output was 4 lamps+ carry, it was a 4 bit
decimal machine.

I thought of converting it to relays, but a straight substitution would
require up to 6 pole units.

No I don't have my copy now, it was from a interlibrary loan :).
A similar book, which I do have is "Computer self-taught through
Experiments" by J. Brayton, publisher Howard Sams, 1968. It used
transistors, the last project was a 10 bit binary calculator. For those who
remember part numbers, it used 50 2N107 transistors + 10 2N322 lamp
drivers, 90 1N34 diodes, etc. for 10 flip-flops.
Received on Tue Mar 02 1999 - 18:29:55 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:32:19 BST