Colossus - The Greatest Secret in the History of Computing

I think one of Churchill’s biggest mistakes was ordering the destruction of Colossus. They probably saw it only as a military asset, but dismantling that and the whole project probably set back UK (and European) computing and science enormously.


Oh, I’d understood that slightly differently. They understood the power of their statistical analysis techniques and the weaknesses of codes, and wanted to keep an advantage in world trade and world power by being able to decode things. So for example the crypto gear helpfully exported to the remnants of Empire was crackable by the UK. And, I thought I’d read that one Colossus may have made its way to GCHQ… indeed, we see this (with a citation!):

Colossi 11 and 12, along with two replica Tunny machines, were retained, being moved to GCHQ’s new headquarters at Eastcote in April 1946, and again with GCHQ to Cheltenham between 1952 and 1954. One of the Colossi, known as Colossus Blue, was dismantled in 1959; the other in 1960.

So, perhaps a setback for science and engineering, but possibly an advantage in power.

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I would have preferred science and engineering :grinning:

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And well, yes, they still kept the edge, that’s what I meant by military asset: it’s military even when it’s peacetime, crypto doubly so. But keeping the tech hidden for 50 years, stupid. (There’s very likely some joint work with the US spooks that still hasn’t seen the light of day.)

Some of it wasn’t hidden or thrown away. I remember an anecdote (perhaps in Turing’s Cathedral) where an early computing group was trying and failing to get their preferred memory technology working. A visiting engineer from England suggested using Williams-Kilburn storage tubes, and said they’d had many years of operational experience with them. Only when the engineer had left did the computing team realize that the years of experience must’ve been during or very soon after WW2.


Regarding memory and secret British WWII developments, the rather implicit way, the concept of stored programs was introduced in the EDVAC paper, always made me wonder, if this was hinting at prior art.

The stored program computer idea is implied in Kurt Gödel’s famous 1931 paper (and Gödel was a close friend of John Von Neumann). It is spelled out even more clearly in Alan Turing’s 1936 paper: while Turing Machines have their programming separate from memory, the Universal Turing Machine stores data and the program of the TM it is emulating in the same tape.

What I was referring to is:
The first notion of a relation between memory and programs is provided in First Draft of a Report on the EDVAC, sect 2.4 (b)

(b) The instructions which govern a complicated problem may constitute a considerable material, particularly so, if the code is circumstantial (which it is in most arrangements). This material must be remembered.

but this isn’t more detailed until sect 14.0, where this is eventually to “be remembered”:

Before we can formulate this code, we must go through some general considerations concerning the functions of CC [central control;NL] and its relation to M [memory;NL].

The orders which are received by CC come from M, i.e. from the same place where the numerical material is stored. (C.f. 2.4 and 12.3 in particular (b).) The content of M consists of minor cycles (c.f. 12.2 and 12.7), hence by the above each minor cycle must contain a distinguishing mark which indicates whether it is a standard number or an order.

That’s it! This I call entering with a whimper rather than a bang. :wink:
(Also, mind that there’s still a categorial distinction between orders and data, even, while both are held in the same memory. A distinction, which was soon dropped, but became of renewed interest, eventually.)
Do we get a theory? No. Do we get considerations regarding feasibility? No. Rather, it’s an implication of the minor cycle architecture (fetch-decode-compute cycle) and its relation to a memory architecture (including a distinction between instruction register and memory buffer register), which isn’t pointed out at that instance. It’s a bit like it should be obvious anyway – to those who are in the know (already?).

Even though Churchill demanded the destruction of the Colossi machines, I think that both Cambridge and Manchester University computer pioneers “hit the ground running” immediately after the end of WWII.

Maurice Wilkes war work had given him to exposure of the mercury delay line stores used in RADAR signal processing, and he was bound to associate with electronic engineers at the Telecomunications Research Establishment, who understood vacuum tube ananlogue and digital circuitry.

The Moore School Lectures of August 1946, attended by Wilkes, was the focal point of post-war computer design and engineering. EDVAC, EDSAC and other notable machines were the outcome of this productive gathering.

Similarly in Manchester, Max Newman (ex Bletchley Park) fouded the Royal Society Computing Machine Laboratory at Manchester and recruited Fred Williams and Tom Kilburn (both formerly at TRE), rapidly got a team established after the war and had the Manchester Baby running it’s first program by June 1948, with Cambridge’s EDSAC running by May 1949.

Although the Colossii were mostly dismantled, and Tommy Flowers was committed elsewhere, I think there was sufficient momentum and sufficient technical personnel available to establish 2 major computing laboratories in the UK.

Despite the secrecy surrounding Colossus, I don’t think the early UK computing pioneers were hindered too much.

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