Acknowledgements

The Moore School lectures

My thanks are due to the Van Pelt Library, especially Nancy Shawcross, for giving me access to the Mauchly papers, and for their pages on the Mauchly Papers Exhibit. I have used these pages and the Historical Monograph "Electronic Computers within the Ordnance Corps", to provide background. The Mauchly Papers pages inspired me to call in to the Library for an all too short period when I had a day free in Philadelphia this year! This in turn inspired me to put some material on the Web about the Moore School Course, and to look for the fourth volume which I did not have time to see. As luck would have it I found a copy of (just) Vol. IV at the The (UK) National Archive for the History of Computing (having reached there via our Departmental Library). The NAHC is in the next building to me! My thanks especially to Jon Agar of the NAHC for providing me with the extended access needed to produce the digest of Vol. IV. A further special thankyou is due to Michael Williams, co-editor of the 1985 reprint, who has since lent me a copy of the book. This should (already has!) enabled me to correct and improve the digest at leisure, and possibly extend it.

My thanks are also due to the Moore School itself, for Paul Shaffer for showing me the ENIAC Museum there, and Professor Mitch Marcus for providing helpful information and advice.

The RCA Selectron in 1946

The 1985 reprint records that in answers to questions the size of the Selectron Tube was given as 5 inches high and 3 inches in diameter, with a planned production of 200 tubes by the end of 1946. In the event the tubes were still not available in the spring of 1948 (or even according to Max Newman by the late summer of 1948), and the IAS computer, for which it had been specifically intended, had to be switched to using a Williams-Kilburn CRT store. (Note that it used the store in a parallel fashion, with a 40-bit word stored in a particular position on a set of 40 tubes, so that it could be accessed in around 1/40th the time.)

The plans for the tube itself were scaled down from providing 4096 bits per tube to 256, with the detail of the design significantly different from that described in this lecture. Ironically, the revised Selectron was used in one of the many machines closely based on the IAS machine, the JOHNNIAC (1953), in preference to the Williams-Kilburn CRTs being used on the others, because of its much greater reliability.


Note that the lecture is 7,500 words long and goes into a lot of detail on alternative ways of grouping the wires (3,000 words) and on describing the electrical/electrostatic mechanisms.


\