The content of this page is taken from "Build your own Computer" (Project Book 057) published in 1973 by Peter Haddock LTD and sold exclusively by Woolworths + Woolco (if you remember these, you are as old as me).

Part One

Early Computers

Most people think of computers as being complicated electronic machines which can work out extremely involved sums in a fraction of a second. In fact, 'to compute' means to count or calculate, and so any device which helps us to count is a computer. Man has been using such devices for thousands of years. Only recently have they become much more complicated.

The earliest method of computing (counting) was by marks — one mark for one, two marks for two, and so on. The Incas, an ancient South American civilisation, tied a knot in a length of string to record each sheaf of grain gathered in at harvest time.

Long ago, merchants and storekeepers used marks on walls to give a tally of their stock, or on containers to show how many articles were in them. Tally marks like this are still used today in some trades. Dockers use them for marking 'counts' of timber when it is unloaded.

Marks are a very simple way of recording a count. But they are not so useful when dealing with large numbers. A tally of, say, seven is quite easy to count, but it takes a little time.

||||||| counts up to seven

But suppose we had a larger number:

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Part Two

Mechanical Computers

Part Three

The Analogue Computer

Part Four

Punch Cards

Part Five

Binary counters

Part Six

Making a computer