Beginnings of a revolution - The Computing Universe: A Journey through a Revolution - page 19

B.1.8. The name of Tommy Flowers (1905-98) is virtually unknown to most students of computing.
His immense contribution to computing and code breaking during the war has only recently emerged
from the obsessive secrecy imposed on the code-breaking activities at Bletchley Park after World War II.
Flowers built an electronic code-breaking machine called Colossus, which was capable of breaking the
so-called Lorenz cipher used by the German high command. Instead of using electromechanical devices
as in the bombes used for breaking the Enigma codes, Flowers decided to use vacuum tubes. This idea
initially met with some resistance because it was generally thought that tubes would not be sufficiently
reliable. Colossus contained about one and a half thousand vacuum tubes and was the world's first
special-purpose electronic computer. Flowers described the heat generated by the computer with the
following words: “Ah, the warmth at two a.m. on a damp, cold English winter!” B3

and provided invaluable information for preparing the Normandy landing. The automated code-breaking
devices such as Colossus and the bombes made a significant contribution to shortening the war ( Fig. 1.21 ).

At the end of the war, Winston Churchill gave orders that most of the ten Colossus machines should be
destroyed. Flowers personally burned the blueprints in a furnace at the Dollis Hill laboratory. The reason for
this destruction was so that the British government could promote and sell Enigma-like machines to other
governments yet still retain the ability to decipher messages sent using
the machines! Two Colossus machines were in use at the UK Government
Communication Headquarters (GCHQ) in Cheltenham until the late 1950s.
With the coming of digital communications, the need for such secrecy
about the wartime activities at Bletchley Park became unnecessary, and
information about Colossus began to emerge in the 1970s. A secret 1945
report on the decrypting of the Lorenz signals was declassified in 2000 and
contains the following description of working with Colossus:

It is regretted that it is not possible to give an adequate idea of the fasci-
nation of a Colossus at work; its sheer bulk and apparent complexity; the
fantastic speed of thin paper tape round the glittering pulleys; . . . the wiz-
ardry of purely mechanical decoding letter by letter (one novice thought
she was being hoaxed); the uncanny action of the typewriter in printing
the correct scores without and beyond human aid. . . .” 18

Fig. 1.21. “We Also Served” - a memo-
rial to code breakers at Bletchley Park.
On the back of the memorial is a quote
from Winston Churchill, written in
Morse code: “My Most Secret Source.”

One clear result of this U.K. obsession for secrecy about its achieve-
ments in computer development during the war years was that all subse-
quent computer developments, even in the United Kingdom, were based
on von Neumann's EDVAC design for stored-program computers.