In the Autumn of 1983, in the face of the phenomenal growth of home computer sales in the U.K., the national British newspaper The Guardian decided to produce, each week, a 'Computer Page'. Noone was quite sure exactly what should go into the page on a regular basis, but it was thought that a fortnightly column on computer mathematics might be a good idea, and when the computer page first appeared on 20th October of that year, it included a small item on binary arithmetic by me.

From the mail I received after my column had been running for a few months, it was clear that the microcomputer age had brought with it a huge increase in the number of (potential) 'recreational mathematicians'. Though in many cases without any formal training in mathematics, my correspondents displayed tremendous mathematical ability, and I was frequently asked if I could recommend any suitable books. What they seemed to want was a genuine mathematics text book, but one which did not require a great deal of prior knowledge. This is intended to be just such a book.