Course Handout - Short-Term Memory Subtypes in
Computing and Artificial Intelligence
Part 3 - A Brief
History of Computing Technology, 1943 to 1950
Copyright Notice: This material was written and published in Wales by Derek
J. Smith (Chartered Engineer). It forms part of a multifile e-learning
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High Tower Consultants Limited.
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First published online 12:12 GMT 27th January 2003, Copyright Derek J.
Smith (Chartered Engineer). This version
[HT.1 - transfer of copyright] dated 12:00 13th January 2010
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This is the third part of a seven-part review
of how successfully the psychological study of biological short-term memory
(STM) has incorporated the full range of concepts and metaphors available to
it from the computing industry. The seven parts are as follows: Part 1: An optional introductory and
reference resource on the history of computing technology to 1924. This
introduced some of the vocabulary necessary for Parts 6 and 7. To go back to
Part 1, click here. Part 2: An optional introductory and
reference resource on the history of computing technology from 1925 to 1942.
This further introduced the vocabulary necessary for Parts 6 and 7. To go
back to Part 2, click here. Part 3: An optional introductory and
reference resource on the history of computing technology from 1943 to 1950.
This material follows below, and further introduces the vocabulary necessary
for Parts 6 and 7. The main sections are: 1 - Computerised Cryptanalysis 2 - The Harvards Mark 1 to 4 3 - The Bell Telephone Laboratories Machines 4 - The Moore School's ENIAC and EDVAC 5 - The National Physical Laboratory Projects 6 - The IAS Machine and the "Eckert-von Neumann"
Architecture 7 - The Engineering Research Associates Machines 8 - The Standards Bureau Machines 9 - The Whirlwind Project 10 - The IBM SSEC 11 - The Manchester University Machines 12 - The Cambridge University EDSAC and the Lyons LEO 13 - BINAC and UNIVAC 14 - Hardware Summary Table, 1943-1950 Part 4: An optional introductory and
reference resource on the history of computing technology from 1951 to 1958.
This will further introduce the vocabulary necessary for Parts 6 and 7. To go
directly to Part 4, click here. Part 5: An optional introductory and
reference resource on the history of computing technology from 1959 to date.
This will further introduce the vocabulary necessary for Parts 6 and 7. To go
directly to Part 5, click here. Part 6: A review of the memory subtypes used
in computing. To go directly to Part 6, click
here. Part 7: A comparative review of the
penetration (or lack thereof) of those memory subtypes into psychological
theory. To go directly to Part 7, click here. To avoid needless duplication, the references for all seven parts are combined in the menu file. To return to the menu file, click here, and to see the author's homepage, click here. We also strongly recommend the computer history sites maintained corporately by the Charles Babbage Institute at the University of Minnesota, the Bletchley Park Museum, the Computer Conservation Society, and the National Archive for the History of Computing at Manchester University, as well as those maintained individually by the University of Essex's Simon Lavington, Clemson University's Mark Smotherman, and the freelance historians George Gray (editor of the Unisys Newsletter) and Ed Thelen. |
1 - Computerised
Cryptanalysis
Clever though the ABC and Z3 (see Part 2) may have
been, the fates chose to ignore them. They were not lucky systems. They
lacked political, financial, and/or academic clout, and as a result simply got
sidelined by history. Atanasoff's
[Codes and
Ciphers in History, Part 1 - to 1852]
[Codes and
Ciphers in History, Part 2 - 1853 to 1917]
..... and readers unfamiliar
with the principles of the German World War Two cipher machines in particular,
should additionally read the third part of said paper, as follows:
[Codes and
Ciphers in History, Part 3 - 1918 to 1945]
1.1 Computerised
Cryptanalysis (1930-1939 - The Polish Bomby)
As explained towards the end of
"Codes and Ciphers in History", the story of mechanically assisted
cryptography began with simple contrivances like Alberti's cipher disk, and moved
on during the 1920s to multiple disk keyboard scramblers such as the German
Enigma system. The technology was then blooded in
Now the reason the Enigma story is
central to the history of computing, is that the Poles also made significant
progress automating the cryptanalytical process. By November 1938, they had
developed a "bomba kryptologiczna", in which six of
their replica Enigmas were mechanically linked together, and motor-driven through
permutation after permutation until the output of one of them matched a pre-set
target value, whereupon the whole contraption stopped automatically, with the
probable Enigma Grundstellung clearly displayed.
ASIDE: The point of using six
replica machines, is that each had its rotors set in a different left-to-right
order, one for each of the Walzenlage permutations possible with a
three-from-three Enigma. The process could have been executed on a single
replica machine, but this would have been able to deal with only one Walzenlage
at a time, so on an unlucky day would take up to six times as long to finish. This
is a very early demonstration of the advantage of parallel over serial
processing. The bomby allowed the Polish cryptanalysts to do all the
necessary trial and error work at machine speed, and the system was so
successful that Bury estimates that the Biuro Szyfrów decoded around
100,000 transmissions in the six years before Poland was eventually occupied.
Kahn (1996, p975) describes the bomby as "the roots of
protocomputers".
Unfortunately, the Poles lost the
naval traffic on 1st May 1937, as a consequence of the Kriegsmarine tightening
its operating procedures [see next section but two], and to rub salt into their
wounds they then lost the army traffic on 15th December 1938, when the
three-from-five Enigma was introduced.
ASIDE: As soon as the Germans
increased the available rotor stock, the number of possible Walzenlage
permutations started to shoot up. For example, there are 10 different ways of
selecting three out of five rotors, and then - as before - six different ways
of sequencing the three you have selected into the available slots, making 60
permutations in all. So in going from three to five rotors, it takes you from
six to 60 permutations: one small step for the cryptographers, but ten times as
much work for your enemies.
But what the Poles were really short
of, of course, was time, and by late June 1939 it was apparent that the German
invasion was not far off. The Polish Chiefs-of-Staff therefore resolved to
share their accumulated Enigma secrets with their French and British allies. An
approach accordingly went out through diplomatic channels, and ended up on the
desk of Commander Alexander G.A. ("Alastair") Denniston (1881-1961).
BACKGROUND: Denniston had been a code
breaking expert during World War One, and had kept "Blinker" Hall's
Room 40 skill base alive by forming the Government Code and Cypher [sic] School
(GCCS) in 1920. He had then run GCCS (known cryptically as "Station
X") as a small peacetime unit attached to the Foreign Office, where it
could serve the diplomatic and peacetime military intelligence worlds. The
organisation was then progressively expanded during the 1930s, as it became
more and more apparent that another war was on its way, and was moved out of
Realising the potential importance
of the Polish work, Denniston personally led a top-secret mission in late July
1939 to the Biuro Szyfrów station hidden in the Lasy Kabackie,
the woods outside Pyry, a small town south of
ASIDE: As head of
The German blitzkrieg against
1.2 Computerised
Cryptanalysis (1939 - The Jeffries Sheets)
Upon Denniston's return from
|
Department |
Officer Commanding |
Team |
Duties |
|
Hut 3 |
Malcolm Saunders Eric (later Sir Eric) Jones (from mid-1942) |
Frederick Norman; Ralph Bennett (from February 1941); William Millward (from April 1942); Telford Taylor (US liaison; from 1943). |
Army and Luftwaffe Enigma translation and initial follow-up (supporting Hut 6). |
|
Hut 3N (= Hut 3/4 Liaison) |
N/K |
Edward Thomas (from February 1942) |
Covered the grey area where army, air force, and navy matters interact. |
|
Hut 4 (aka "Naval Section") |
Walter Eytan (Z Watch, from February 1941) |
Harry Hinsley (from October 1939); Alec Dakin (from May 1940), Patrick Wilkinson; Charles Leech, Gordon Priest, Eric (later Sir Eric) Turner, Ann Toulmin; Leonard Forster; Ernest Ettinghausen; Thelma Ziman; Vivienne Alford; Peter Twinn |
Naval Enigma translation and initial follow-up (supporting Hut 6). |
|
Hut 6 |
Gordon Welchman (September 1939); Stuart Milner-Barry (1940) |
Derek Taunt; Dennis Babbage |
Army and Luftwaffe Enigma primary cryptanalysis. |
|
Hut 8 |
Commander Edward (later Sir Edward) Travis Alan ("Prof") Turing |
Joan Murray (June 1940); Hugh Alexander; Alex Kendrick; Jack Good (May 1941 to April 1943); Hugh Foss; Leslie Yoxall; Shaun Wylie; Michael Ashcroft; Richard Pendered |
Naval Enigma primary cryptanalysis. |
|
The Newmanry |
Max Newman (from September 1942) |
Jack Good (from May 1943); David Rees; Bill Tutte |
|
|
The Testery (Part of Block F) |
Major Ralph Tester |
Roy Jenkins; Alan Turing; Peter Benenson; Peter Hilton; Donald Michie |
|
|
Hut 7 |
John Tiltman |
|
|
|
The Cottage - Intelligence Sections OS and K |
Oliver Strachey (= OS) and Dillwyn Knox (= K) |
John Jeffries; Keith Batey; Mavis Lever; Margaret Rock |
Abwehr non-Enigma and Enigma traffic respectively - cryptanalysis and onward despatch. |
Denniston's strategy immediately led
him to a young mathematician named Alan Turing .....
ASIDE: In wartime, the military draw
heavily on the services of civilian academics and engineers, especially in the
areas of physics, mathematics, and telecommunications. These were routinely
referred to as "boffins", and in this section we meet one of the
boffinest, Alan Mathison Turing (1912-1954). Turing had achieved early
academic fame with a 1937 paper entitled "On computable numbers, with an
application to the Entscheidungsproblem" (Turing, 1937). In this
paper, he proposed a hypothetical decision-making machine, fed with a series of
simple yes-no questions from a paper tape input. The philosophical issue was
whether there was any mathematical problem which could not be programmed
in this way (Turing used the phrase "calculable by finite means").
Turing concluded that in fact there were such problems, albeit not many,
and his hypothetical machine is now commonly seen as the idealised binary
digital computer, or "Universal Turing Machine". The Turing Archive for the History of Computing and the King's
College Cambridge Turing Digital Archive contain digital facsimiles of
many of Turing's wartime papers, now declassified.
Turing reported for duty on 4th
September 1939 (Hodges, 1992), and was joined shortly afterwards by another
By December 1939, the new
"Jeffries Sheets" were ready (60 sets, one for each possible Walzenlage
again, and each set containing 26 matrices), and by one account Turing
delivered them in person to Rozecki, Zygalski and Rejewski, now codenamed
"Equipe Z" (= "Team Z"), at Vignolles, where - after just
over a year in the dark - they enabled the first successful decryption of a
three-from-five Enigma on 17th January 1940.
The Allies were now free to
resurrect the principles of the Polish bomby, namely to work through the
Walzenläge from the first to the 60th, searching for a fragment of
pre-set "cribtext" .....
Key Concept - The "Crib":
Cryptologically speaking, a "crib" is a short fragment of known or
strongly suspected ciphertext content. Many cribs derived from the repetitive
nature of military communication. For example, many units reported
NICHTSZUMELDEN (= "nothing to report") on a daily basis, or their
radio operators would send a pro forma tuning message before anything else
(Taunt, 1993). The other main sources of cribs were (a) weather reports, (b)
proper names, (c) plain old-fashioned operator bad practice, and (d)
deliberately creating an operational event and then checking to see how it was
reported the next day (a process known as "seeding").
The Enigma cribs were given added
importance by one of the system's basic design features, namely that no letter
was allowed to encrypt as itself. This meant that if you aligned a slip of
cribtext above a line of ciphertext, no vertical pair of characters could be
the same. If they were, then the crib could not exist at that position.
Milner-Barry (Hut 6) summarises the argument this way:
"If, for example, you were looking for the
most likely position [for the word] Besonderen [= "special"],
and you noticed that under the [cribtext] B in Besonderen was another B,
you would know for a certainty that that could not be the right position."
(Milner-Barry, 1993, p94.)
It followed that if a crib could be
logically excluded in all text positions, then either (a) the crib was
wrong, or (b) the crib was right, and that particular machine setting could
be excluded; and on most days, on routine intercepts, you had very high
levels of confidence in the crib. Taking this argument a step further, if you
could carry out this process of elimination at speed and exclude all machine
settings except one, then that would be the one to use to decipher that day's
intercepts.
1.3 Computerised
Cryptanalysis (1940-1941 - The Bombes)
Key Locations - BTM: In this section,
we meet "BTM", the British Tabulating Machine Company premises at
Letchworth, Hertfordshire. BTM was formed in 1908, as a London-based licensee
of Hollerith punched card technology (see Part 1). The company was renamed
International Computers and Tabulators in 1959, acquired Ferranti's computing
division in 1963, and merged with English Electric to form International
Computers Ltd (ICL) in 1968. ICL was the British computing industry
in the 1970s and 1980s, but was taken over by Fujitsu Corporation in 1990. The
marque was finally withdrawn (for marketing image purposes) in 2001.
The bombes were put together by BTM
at their Letchworth factory, and Welchman (1982) dates the experimental systems
to September 1940 (the first was nicknamed "Agnes"). However,
Welchman also estimates that it took another year or so before they started to
take the pressure off the pen-and-paper techniques. Indeed, Welchman repeatedly
stressed that the bombes themselves did not break codes, but that people did.
The processing logic meant that the more machines you had, the shorter could be
the Walzenlage tape for each, and the quicker you could get your
results. About six bombes were operational by mid-1941, and perhaps twelve by
late summer (Welchman, 1982). Production then proceeded at about one machine
per week, the machines being transported from the BTM factory without escort to
avoid attracting anybody's attention. Different machines serviced different
huts, and different regional or administrative networks within huts. Worthwhile
intelligence started to appear in the July 1940 defence of
1.4 Computerised
Cryptanalysis (1941-1942 - The Naval Enigmas)
With the German army and air force
codes under some semblance of control, attention turned to the Kriegsmarine
system. This had been a much tighter system since the introduction of more
vigorous procedural protection for the message header on 1st May 1937, but it
was nevertheless strategically vital for it to be defeated, because it was the
key to countering the German U-boat offensive. This is how Irving John
("Jack") Good (1916-), who joined the team in May 1941, summarised
the complex Kriegsmarine operating procedure [we recommend sketching out his
worked example as you go]:
"The German operator would haphazardly
choose the settings for the three wheels as shown by the rings, say ASC, but he
would not send ASC in clear. Instead, he would first set the wheels at [the key
of the day] Grundstellung [and] tap out ASCASC. [This] would give him a
hexagraph, say LQRCPY. He would write this in the pattern [L over space, Q over
C, R over P, and space over Y] and fill in the [resulting four-by-two]
rectangle with two letters that he chose haphazardly. For example [O bottom
left and T top right]. Next he would encrypt the vertical digraphs LO, QC, RP,
and TY by using a secret 'digraph table'. There were ten possible digraph
tables (fixed for an appreciable time, perhaps of the order of a year), and
which of the ten he was to use would be shown by part of the keys of the day.
For example, LO might become
Fortunately, May 1941 turned out to
be a doubly lucky month for British codebreaking. Firstly, a copy of the June
1941 codebook was recovered from a captured German trawler, and secondly one of
the machines itself was recovered from a captured U-Boat (U-110). This gave
sufficient specific background information for the naval Enigma to be
effectively broken for the remainder of that year. Then came more ominous news.
Thomas (Hut 3N) tells how in August 1941 he inspected the inside of captured
U-570 (Thomas, 1993). No code books or machines were recovered on this
occasion, for the crew had ditched these over the side, but what they had not
ditched was the transportation box for a machine still under test, which, Thomas
noted, was recessed to accommodate a four-slot machine, rather than
three. It subsequently transpired that the Kriegsmarine was about to upgrade to
a four-from-eight Enigma system, and when this eventually went live in February
1942 it brought blackout for the rest of that year, (a) because there were new
rotors whose internal wiring needed to be broken, and (b) because the
cryptanalysts now had many more permutations to wade through at run time.
ASIDE: The 1942 naval Enigma
machines were not just fitted with four rotors rather than three, but some of
the rotors had more than one turnover notch, so they would "carry" to
the adjacent rotor more often. As previously explained, there are 60 Walzenlage
permutations on a three-from-five Enigma. If we do the same calculation with a
four-from-eight naval Enigma we find there are 70 ways of selecting four
rotors, and then another ten ways of sequencing the rotors-of-the-day across
the available slots, making 700 permutations in all. (In fact, it was not quite
as bad as this, because German operating procedures insisted that at least one
of rotors VI to VIII was included.)
The four-from-eight naval system
therefore demanded either more bombes or a more sophisticated computational
solution, and, according to the Bletchley
Park Museum, eventually around 200 machines were in operation 24-hours a
day at sites across
1.5 Computerised
Cryptanalysis (1942-1943 - Breaking the Lorenz SZ42)
Key Location - TRE: The next part of the story of
British World War Two code breaking introduces another important location - "TRE",
the Telecommunications Research Establishment, Malvern, Worcestershire. This
began life as an Air Ministry project to develop top secret radar equipment.
Funding was authorised in 1934, and a small team was brought together in 1935
under Robert (Later Sir Robert) Watson Watt (1892-1973) at Orfordness,
Key Personnel: In this section, we also meet
Maxwell Herman Alexander ("Max") Newman (1897-1984), a senior
Cambridge mathematics professor before the war, who had lectured Turing as a
student (in fact, it was he who had inspired the latter's Entscheidungsproblem
paper and established the academic links with Princeton which had brought
Turing into contact with von Neumann). We also meet again the Welsh physicist Charles
E. Wynn-Williams (1903-1979), whose pre-war track record building
electronic counting circuits was about to prove invaluable (remember that he
beat Stibitz to the binary accumulator by six years - see Part 2). Wynn-Williams joined
AMRE/TRE from
Important though they were, the
Enigmas were only tactical systems. Their job was to link Hitler's generals to
their armies, his air marshals to their airbases, and his admirals to their
U-boats and surface units. The various networks carried routine low-level
orders in bulk, that is to say, the sort of traffic required to move and
coordinate Hitler's war machine in much the same way that our motor nerves move
and coordinate the individual muscles of our bodies. Yet another encryption
system serviced strategic communication between the High Command and the far
corners of the German military and diplomatic world; and, needless to say, one
high level message could easily tell you as much as a few thousand day-to-day
ones. The Germans therefore protected their strategic communications traffic
with higher specification cipher machines - the Lorenz Schlüsselzusatz
SZ40/42 [picture]
and the Siemens and Halske T52 Geheimschreiber [picture].
The SZ42 was a Vernam-style
bit-flipping teletypewriter, as previously described [background]. Using
the commercially widespread system of five-hole tape [see under Morkrum
and Morkrum-Kleinschmidt in Part 1], it
carried out a key-controlled modulo 2 encryption of every bit in every
character in the plaintext. It then produced a pre-perforated ciphertext tape
for transmission, and the transmission itself was done at machine speed in ITA2 [details], rather
than at human speed in Morse Code. After each character, the encryption key was
varied according to an advancing rotor system, not unlike the Enigma, only
there were now twelve rotors, and they had many more pins. The Germans named
this system Lorenz, after the Lorenz Teletypewriter Company which manufactured
it, whilst the British named the equipment "Tunny" and its
transmissions "Fish". The first Fish intercepts started to come
through in the summer 1940. The British codenamed the Geheimschreiber
"Sturgeon", after it was discovered being used for high level
Luftwaffe communications from late 1941 (Hinsley, 1993). A full GCCS report,
the "General Report on the Tunny" is available in digital
facsimile, if interested. Unlike the various Enigma systems, the Lorenz
systems could encipher letters as themselves.
The basic principles of the Lorenz
code were initially unravelled by Colonel John Tiltman, head of the Military
Section, and subsequently fleshed out by William T. ("Bill") Tutte
(1917-2002), who had joined GCCS fresh from university in January 1941.
ASIDE: It subsequently emerged that
the Siemens and Halske system had already been cracked by the Swedish
cryptographer Arne Beurling in June 1940 (Beckman, 1996). The German diplomatic
telegraph cable passed through Swedish waters, and had been duly tapped by
Swedish Telecom. All Geheimschreiber traffic from the day the system was
first tested on 18th April 1940 was intercepted, and closely studied by
Beurling. He broke the code later than summer, using pen and paper
cryptanalysis and sheer force of logic. It took him a fortnight, although he
too was helped by some sloppy operator discipline. Professional to the last,
Beurling died leaving no published explanation of how he broke the Geheimschreiber:
"A magician," he insisted, "does not reveal his secrets". For more on cryptology in
general, and teletype systems in particular, we recommend "Toby's
Cryptopage" (2002
online).
Tutte was given a good start by an
unsafe transmission on 30th August 1941 from a German operator in
ASIDE: It is difficult to get a
straight story from the literature here. Retransmission of a pre-perforated
teleprinter tape would not, of itself, normally require a re-encryption, and
would simply produce an identical copy. Nevertheless, the online Tunny Report
(above) clearly states (p298) that the retransmission had been rekeyed to tape,
complete with minor mispellings.
By painstakingly analysing those
ciphertexts over a period of several months, Tutte and his colleagues
eventually correctly deduced that the Lorenz machine had to consist of 12
different sized rotors, of size 23, 26, 29, 31, 37, 41, 43, 47, 51, 53, 59, and
61 (Good, 1993).
ASIDE: The Geheimschreiber,
by contrast, had ten such wheels, sized 73, 71, 69, 67, 65, 64, 61, 59, 53, and
47. Full details in Beckman (2003).
Aside from the rotor sizes, it was
also necessary to learn the logic of their gearing. To start with there were
five K (or chi) rotors (the 23, 26, 29, 31, and 41 pin ones), then there were
five S (or psi) rotors (the 43, 47, 51, 53, and 59 pin ones), and finally there
were two M (or mu, or motor) rotors (the 37 and 61 pin ones). This is how they
worked together .....
"The first set of coding wheels, K1-K5,
and the first motor wheel, stepped every time. The second motor wheel stepped
whenever the first motor wheel pattern enabled it to do so. The second set of coding
wheels, S1-S5, stepped whenever the second motor wheel enabled it to do
so." (Halton, 1993, p172.)
Halton continues .....
"Whether or not a coding wheel reversed
the sense of the digit passing through it depended on the setting of a tooth on
its circumference, the tooth being either erect or folded down. The wheels all
had different numbers of teeth, which were set up to the pattern specified for
the day [Ed. in much the same way that we nowadays set the timer pins of
central heating or pre-programmed lighting systems], and all could be rotated
individually to any required position for the start of a message. The first set
of wheels advanced one tooth for every character. Two more wheels of a similar
type controlled the stepping of the second set of coding wheels and were called
(at BP) the motor wheels. The first motor wheel advanced by one tooth for every
character, but the second did so only when permitted to do so by the teeth of
the first. The second set of coding wheels stepped only when permitted to do so
by the teeth of the second motor wheel. Like the character-coding wheels, the
motor wheels could be set to any specified tooth pattern and could be made to
start from any position." (Halton, 1993, p169-170.)
Gil Hayward (1993), one of the
Tunny engineers, adds:
"Each rotor [in the first group of five]
was advanced by one tooth for each character transmitted []. The enciphering
was achieved by [exclusive-OR addition.] We knew this process as 'non-carry
binary addition' [] The second set of rotors was driven indirectly via the [two
M-rotors] and now processed the [five code] elements once more, performing an
exclusive-OR of the output of the first set with their own tooth states. The SZ
sent the final element outputs to line in serial form in real time."
(Hayward, 1993, p178.)
Remembering that the electrical
principle was that five bits Baudot-Murray code in should give five bits
Baudot-Murray code out, here is a diagram showing how the input pulses were
routed through the K- and S- wheels of the SZ42 .....
DIAGRAM UNDER CONSTRUCTION
Tutte's decryption has been
described as arguably "the greatest intellectual feat of the whole
war" (
This time it was Wynn-Williams and
his high-tech TRE team who put the hardware together, and the resulting
computer, codenamed the Heath Robinson, was operational around April
1943. Here is Michie's own summary of its working principles:
"The [Heath Robinson] machine incorporated
two synchronised photo-electric paper tape readers, capable of reading 2000
char/sec. Two loops of 5-hole tape, typically more than 1000 characters in
length would be mounted on these readers. Counts were made of any desired
Boolean function of the two inputs. Fast counting was performed electronically,
and slow operations [] by relays. The machine, and all its successors, were
entirely automatic in operation, once started, and incorporated an on-line
output teleprinter." (Michie, cited in Randell, 1976/2002 online, p9.)
Good (1993, p162) adds:
"The input to Heath Robinson was a pair of
teleprinter tapes, one containing cipher and the other one some function of the
chi wheels. The tapes would be stuck into closed loops and driven partly by
pulleys and partly by their sprocket holes. Both tapes would be read
photoelectrically and the innards of the machine would count the number of
times that some Boolean function was equal to a dot. The cipher tape would have
a length prime to that of the key tape, so that in the course of a 'run' all
possibilities were examined. The machine had perhaps about two dozen vacuum or
gas-filled valves or tubes. [] The main weakness of the design was the driving
of the tapes partly by their sprocket holes at about a hundred times the speed
of the tapes in normal teletypewriter usage. This would cause these holes to
stretch and the tape to have a tendency to tear [.....] Also, from time to
time, the machine would begin to smoke."
1.6 Computerised
Cryptanalysis (1943-1945 - The Colossus)
Key Locations - "Dollis Hill": The third part of the
story of British World War Two code breaking involves workers at another
important location - "Dollis Hill", the Post Office Research Station,
at Dollis Hill,
Key Personnel: In this section, we meet Thomas
Harold ("Tommy") Flowers (1905-1998), a telecommunications
engineer at Dollis Hill. Flowers was an experienced electronics designer, and
had been experimenting with valve technology in telephone switching gear since
1931.
The Robinsons were transitional
machines; faster than the bombes, but still largely relay-based, experimental,
and with the reliability problems mentioned above. The decision was accordingly
taken to build a machine which would be faster still and have greater
processing power, and in order to achieve these higher speeds, valves were
going to have to replace relays wherever possible.
The detailed design for Colossus was
teased out in the winter of 1942/3 by Newman and Flowers, with major
contributions from Good and half a dozen others. The Dollis Hill group, now
with additional assistance from W.W. Chandler, then spent the first eleven
months of 1943 putting the machine together and testing it, and it began
productive work in December 1943. The Colossus consisted of 1500 valves,
weighed about a ton, and could make do with only a single input paper tape,
from which data could be read at the rate of 5000 characters per second. To
reduce tape handling failures, the cipher tape was read once, and its contents
written to memory (this was the essence of the advance over the Heath Robinson,
and accounts for the much higher number of valves used). Thyratron valves were
included as memory units.
The British now had significant
access to German communications at the highest level, and the team's early
successes included forestalling the German counter-attack against the
Here is an analysis of the
COLOSSUS's strengths and weaknesses, measured against the criteria of modernity
discussed so far .....
|
Electronic rather than Electromechanical |
Digital rather than Analog |
Binary rather than Decimal |
General Purpose Stored Program |
|
Yes |
Yes |
Yes |
General purpose in principle, but in practice all the input-output peripherals were tuned for code-breaking applications, so considerable reconfiguration would have been necessary. Externally programmable due to shortage of memory. |
ASIDE: A moment's pause before
moving away from the codebreaking applications. It is nowadays altogether too
easy to be carried away with the technicalities of cryptology, and we should not
forget that lives were at stake every minute of every day. When you broke
a code, these tended to be your enemy's lives, and when you did not, they were
your own. Either way, the casualties were real people, not numbers. Dakin (1993)
recalls being emotionally moved later in the war by the number of German
sailors receiving messages telling them that their homes had been AUSGEBOMBT,
and Eyton (1993) reports being unable - then - to make sense of a curious
phrase from an Aegean maritime intercept later in the war, when a cargo of Jews
was reported as being en route for the ENDLÖSUNG (= "final
solution"); the code, on this occasion, was stronger than the cipher! On
the lighter side, Jack Good, it is reported, went out of his way to acquire an
"007" car registration plate once the James Bond stories hit the
headlines in the early 1960s, and drove it, no doubt, with a cryptic smile. To see what Hut 4 is doing
nowadays (31st May 2003), click here.
2 - The Harvards
Mark 1 to 4
The Harvard Mark 1 was a joint
venture between IBM and
The Harvard Mark 1 was the largest
(55 feet long, 8 feet high, and containing over three quarters of a million
parts) electromechanical calculator ever built. It was sited at the IBM
installation at Endicott, NY, and (like Colossus) was something of a
"transitional" species, retaining moving parts characteristic of the
old da Vinci machines, but incorporating Babbage-style modularity and
programming (not surprising, since Aiken had explicitly based his first-cut
design on Babbage's four main modules - see Part 1). It
received its processing instructions on previously perforated paper tape, and
data input/output on punched cards. It was fitted with 72 23-decimal-place
registers (one of the 24 decimal wheels making up each register was reserved
for use as a sign digit), each cannibalised from IBM's pre-war range of
electromechanical calculators, and was thus capable of doing very big sums to
very high levels of accuracy. These registers were "accumulators" -
they would store whatever number was put into them until next required, and
then allow it to be added to. A further 60 registers were "read
only", and were manually set to program constants prior to the run
commencing. Each tape-punched instruction served to identify the next operation
to be carried out, together with the location of the registers containing the
operands for that operation and the destination of the answer. The main drive
shaft rotated at 200 rpm, meaning that the machine could work at the rate of
just over three "elementary operations" (such as simple additions)
per second.
The system remained under trial and
improvement until mid-1944, whereupon it was shipped lock, stock, and barrel to
the Harvard Computation Laboratory. It was then immediately leased by the US
Navy's Bureau of Ships - no less than three admirals being present at the
official inauguration on 7th August 1944 (Williams, 1999) - and put to work in
aid of the war effort, with armed guards patrolling the campus. It continued in
service until 1959. An improved version of basically the same design was laid
down in 1942, for installation at the US Naval Proving Ground,
Here is an analysis of the first two
Harvard machines' strengths and weaknesses, measured against the criteria of
modernity discussed so far .....
|
Electronic rather than Electromechanical |
Digital rather than Analog |
Binary rather than Decimal |
General Purpose Stored Program |
|
No - electromechanical |
Yes |
No - decimal (a hangover from the days of the desk calculator, and a major design weakness) |
General purpose, within the limitations of its rudimentary instruction set, but not stored program. |
3 - The
Bell Labs began their involvement
with computers following Stibitz's experiments with binary adding circuitry in
1937 (see Part 2),
and although they started after Aiken their machines were much smaller and thus
a lot quicker into service. Samuel B. Williams led their Model 1 Relay
Calculator project (aka the "Complex Number Computer"), and had the
product ready for action in January 1940. It was publicly demonstrated in
September 1940, being operated over a teletypewriter link. It was not
programmable, however, and this defect was remedied as an adjunct to Bell's
work on flak systems in the Model 2 Relay Calculator (or "Relay
Interpolator"), a tape-controlled device with self-checking arithmetic.
This became operational in September 1943 at the US National Defence Research
Council, where it was initially used to produce lifelike test data for
The limiting factor in all these
machines was still the technology. Circuits were hand-built and hand-soldered out
of individual capacitors, valves, and resistors, mounted on a metal chassis.
The machines worked, but only after a fashion - they were big, heavy, got very
hot, and kept breaking down as fuses blew, switches failed, and valves burned
out. The next breakthrough came in 1947, when John Bardeen, Walter H. Brattain,
and William Shockley - more Bell Labs researchers - brought together a number
of earlier discoveries and invented the "transistor", a
development for which they were awarded the 1956 Nobel Prize for Physics .....
Critical Invention - The Transistor
(1947): A transistor is a "cold-running" electronic
switch. In its original form it consisted of a "semiconducting" -
that is to say, unidirectional - crystal of germanium, onto which was placed a
metal contact. This "point contact" device made use of fundamental
properties of this type of interface, namely that electrons are drawn away from
the contact more easily in the conducting medium than in the non-conducting
crystal. Such units could therefore be installed in electronic circuits in
place of valve diodes, where they would rectify AC the same way, but with no
need either (a) for a heating current, or (b) for a glass capsule. They
therefore allowed the work of the thermionic valve to be done at fractional
cost, size, and power. A different layout followed shortly, in which two
point contacts were applied to one face of the crystal, and a flat contact on
the opposite face. This served in place of valve triodes, allowing one part of
a circuit to switch the current flowing in another part.
4 - The
"There are 10 types of people in the world
- those who understand binary, and those who do not" (Anonymous Internet
wag, October 2002.)
As with the British codebreaking
machines, the major historical step away from electromechanical architectures
in the US came in 1943. This was when the Moore School of
Electrical Engineering at the
Enter John William Mauchly
(1907-1980), a
Brainerd was successful, and the
contract for ENIAC was duly signed in June 1943. The project proceeded under
the codename "Project PX". Brainerd was appointed project manager,
Eckert chief engineer, and Mauchly principal consultant (Moye, 1996). Others
involved were Arthur W. Burks, Thomas K. Sharpless, and Robert F. Shaw.
Eckert's initial role was to increase the average life expectancy of the
electronic valves which were going to be required, because the fact that large
numbers of them were going to be used meant that the final system was otherwise
at risk of being permanently out of service.
ASIDE: The problem of valve
burn-out, it will be recalled, had been Zuse's worry back in 1938, when he
elected to keep the Z3 project electromechanical - see Part 2. However Tommy Flowers'
advice on the Colossus development had been that the majority of valve failures
took place when they were warming up, and that systems which could be switched
on and left on were much less vulnerable. That and high specification
manufacturing brought performance up to acceptable standards.
Eckert was also responsible, he
later recalled, for testing whether the
Thanks to its electronics, the ENIAC
was nearly 2000 times as fast as the ASCC, leading Eckert, rather
disparagingly, to dismiss the rival Harvard machines as just "fancy
tabulators". Around 5000 simple additions were possible per second
(compared to the Mark 1's three). Moye (1996) explains that ENIAC could do in
30 seconds what took the Bush differential analyser 15 minutes (far less
accurately) and a skilled mathematician 20 hours; one commentator even pointed
out that it was faster than the projectiles it was tracking. The system was
decommissioned in 1955. [To see the wording of the US War Department's public
announcement of the project in 1946, click here.]
Here is an analysis of the ENIAC's
strengths and weaknesses, measured against the criteria of modernity discussed
so far .....
|
Electronic rather than Electromechanical |
Digital rather than Analog |
Binary rather than Decimal |
General Purpose Stored Program |
|
Yes |
Yes |
No - decimal, 10 places of. |
General purpose, but not stored program. |
The ENIAC profile table still contains
two significant NO entries - it computed in decimal rather than in binary, and
it had no memory to spare for program storage. In the world of computer design,
these are both signs of considerable immaturity, but the decimal issue
represented by far the greater practical barrier, for it is an example of how
"functional fixedness" can impede technological innovation. As with
the Harvard Mark 1, the ENIAC's designers thought in decimal, and so presumed
that their creation should do likewise. "Proper" computers, on the
other hand, were already computing in binary rather than decimal. Wynn-Williams
had seen this, Zuse and Stibitz had seen this, and so too had Atanasoff, but
the Harvard and Moore School teams had simply built decimal logic circuits out of
binary basics, and, for technical reasons beyond the scope of this paper, that
was actually a circuit designer's nightmare.
ASIDE: Upon learning after the war
that the Americans had used 18,000 valves in their ENIAC, Zuse is reputed to
have shaken his head and asked what on earth they had all been for. He and
Schreyer had studied valve-based logic circuits in 1936 (see Part 2), and knew that a binary
system of ENIAC's overall capability should need less than 3000 valves, that is
to say, ENIAC was an order of magnitude larger than it strictly needed to be.
This is a measure of the inherent inefficiency of trying to do decimal
computation with essentially binary hardware.
In March 1946, a dispute broke out
between Eckert and Mauchly on the one hand, and the
The decimal-binary issue was not
fully resolved until 1946, when the Hungarian-American John von Neumann
(1903-1957) joined the Moore School team, just as they began work on the
Electronic Discrete Variable Automatic Computer, or EDVAC, the ENIAC's
replacement. Von Neumann had visited the ENIAC development in August 1944, as
part of his fact-finding duties as academic advisor to a number of US
government agencies, and had followed this up with a paper extolling the
virtues of all things binary in 1945 (von Neumann, 1945/1982).
Now the beauty of binary is that it
simultaneously eases data transmission and manipulation. In binary computing
machines, information is stored in "binary digits" (or "bits"
for short) [the term "bit" was introduced in the early 1950s by the
The time was now right to share a
few of the secrets, and the Moore School therefore took the very farsighted
step of ensuring that everyone in the rapidly burgeoning industry would all be
singing from the same hymn book. Between 8th July and 31st August 1946,
they ran a 48-lecture course entitled "Theory and Techniques for Design of
Electronic Digital Computers". There were 28 officially named attendees,
including Maurice
Vincent Wilkes (Cambridge), and Bletchley Park's Irving J. ("Jack") Good
and D. Rees (both by then at the University of Manchester), and they were
taught by experts drawn from the Harvard and Moore School teams.
EDVAC's sponsor was the BRL at
|
Electronic rather than Electromechanical |
Digital rather than Analog |
Binary rather than Decimal |
General Purpose Stored Program |
|
Yes |
Yes |
Yes |
Yes |
Note that we now have a run of four straight
yesses across the EDVAC's key points profile, as a result of which many
commentators rate it as the class-defining modern computer - the first working
"Eckert-von Neumann machine" (see next section but two). The EDVAC
should also get the credit for including the first workable "Operating
System" (see Part 4), and for
solving the problem of program "branching", known officially as
"conditional control" .....
Key Development - Conditional
Control: This is a facility whereby one machine instruction
moves not to the immediate next but to the beginning of a logically related
series of instructions further down or further up the program. This gives the
programmer the ability to apply a degree of modularity to the totality of his
logic. It is a vital part of effective programming, and will be further
discussed in Part 5 and Part 6.
5 - The National
Physical Laboratory Projects
Background:
Many Colossus personnel were
transferred to the NPL after the war, including Alan Turing in October 1945 to
lead their computerisation efforts. By 1946 Turing had compiled plans for a
machine which was grandly intended to resolve, given the right programming and
sufficient run time, any computable problem. It was thus a physical realisation
of his hypothetical "Turing Machine", and was originally intended to
be bigger in terms of processing power than all the
ASIDE - System Acronyms: Computing has a
long tradition of the contrived computer acronym. Unlike ENIAC and EDVAC, the
ACE was deliberately greater than the sum of its initials. There are similar
"in jokes" with LEO, the Lyons machine, the fact that ACE was
followed by DEUCE, and the fact that many nuclear weapons calculations during
the 1950s were carried out, literally, by a MANIAC.
The project did not make much
progress, however, primarily because it was technically over-ambitious. The
design called for a number of huge technical steps forward (not least a number
of parallel processors and a convoluted instruction set), and was accordingly
going to require more staff than were available (Flowers, for example, declined
an offered post because he was busy repairing the nation's war-damaged
telephone system). By December 1946, things had got so bad that the NPL
directors called upon one of the delegates to the Moore summer school,
Cambridge's Maurice Wilkes, for an opinion on the project's viability, and he
wisely suggested that a scaled down version of the system be put together to
test the basics (Wilkes,
1946). This was called the Pilot ACE.
In 1948, Turing transferred to Max
Newman's laboratory at Manchester, and the Pilot ACE continued in development
for two more years under James H. Wilkinson and E.A. Newman, and executed its
first program on 10th May 1950 (making it, they claim, the fourth group in the
world to deliver a stored program electronic digital computer), and was
publicly demonstrated in December that same year. It contained a mere 800
valves, could perform 16,000 simple additions per second in optimal conditions
(making it very fast for its day), and input and output were on punched cards.
The machine also had available 18 delay lines (eleven slow ones, each capable
of storing 32 32-bit words, and seven smaller but faster) .....
Key Development - Delay Lines: This was
an apparatus capable of maintaining an electrical pulse train indefinitely, by
constantly using it to repropagate itself. The British National Physical
Laboratory (see next section) commissioned Dollis Hill's Flowers and Coombs to
do some basic research here in June 1946, and they had a prototype 1000-bit
delay line working in January 1947. The most common form was the "mercury
acoustic delay line", an elongated bath of mercury, some one to two metres
long, with a crystal oscillator at both ends. The pulse train was input to the
oscillator at one end, and thereby generated a matching pressure wave (push or
no-push) within the mercury. This was then detected by the oscillator at the
far end, and converted back into electrical pulses. Typically about sixteen 35-bit
words would be in transit between the oscillators at any one time, arriving at
around one bit per microsecond. The processor had to wait for the desired word
to arrive at the far end before it could retrieve it, which was a major source
of microdelay. Delay lines were used on the EDVAC, Pilot ACE, EDSAC, BINAC, and
UNIVAC systems, and can be described as reliable but slow.
Another GCCS veteran, Treorchy-born Donald W. Davies (1924-2000),
joined the project as a mathematician in September 1947, and made important
contributions to the final design. He also coded an early noughts-and-crosses
computer game before going on to become a major force in packet-switching data
transmissions (an ancestor of today's Internet). Pilot ACE was decommissioned
in June 1956, and its main components are in the Science
Museum. Work on the larger follow-up machines, DEUCE, Full ACE, and the
American ACE-clone, the Bendix G15, is described in Part 4. The NPL
was also involved in one of the early defence computers, MOSAIC.
6 - The IAS Machine
and the "Eckert-von Neumann" Architecture
Having influenced the design of the
Alert readers will have noted how
John von Neumann's name has occurred several times so far. Basically, this is
because he had established a considerable reputation as a mathematical genius
before the war. He had joined the staff at
Above all, von Neumann had used the
war years to crystalise a particular technical vision of how digital computers
ought to work, and in the closing months of the war he drew up the plans for
what came to be called the "von Neumann architecture" for a
"general purpose computer" (GPC). His proposals were published in
Goldstine and von Neumann (1945), von Neumann (1945), and Burks, Goldstine, and
von Neumann (1946), and did much to foster the necessary common understanding
and standardisation of approach.
ASIDE: The technical vision was not
uniquely von Neumann's, but only he combined the understanding with a position
of sufficient influence to do something about it (Zuse, by contrast, was
probably technically ahead in 1946, but was working on a shoestring in a
country ravaged by war).
In the
remainder of this paper, we are going to follow Maurice Wilkes' argument
(Hipwell, 1999) that ENIAC's Presper Eckert contributed at least as much real
substance to this architecture as the more theoretical von Neumann. He
therefore prefers the term "Eckert-von Neumann architecture".
In the event, there was little
disagreement over von Neumann's proposed macro-architecture, because in terms
of its main modules it was essentially little different to Babbage's Analytical
Engine, a century beforehand [see Part 1]. To qualify as an "Eckert-von
Neumann machine", a computer has to have a number of particular qualities:
- it needs to be electronic not electromechanical
- it needs to be digital not analog
- it needs a binary micro-architecture, not decimal
- it needs to be functionally organised so as to
have separate modules for (1) memory, (2) control unit, (3) calculation,
and (4) communication with the outside world (ie. input/output, or
"I/O" for short), all interconnected by a wiring loom known as
the "bus" (a term derived from the "bus-bars" used to
carry signals around the old electromechanical switching gear).
- it needs to run binary stored programs from
memory, accessing binary data temporarily in that same memory (from which
it follows that the control unit must be able to tell the one type of
content from the other - or else).
These were the design concepts put
across at the 1946 Moore School summer school, and they influenced the design
of every machine then in the pipeline except the decimal computer ENIAC, which
was already too near completion to do anything about. Specifically, it evolved
into Williams and Kilburn's Manchester Mark 1, the NPL's Pilot ACE, Eckert and
Mauchley's BINAC, the
7 - The Engineering
Research Associates Machines
Engineering Research Associates
(ERA) was formed in January 1946 by a team of experts from the American wartime
cryptanalysis effort. They were led by Howard T. Engstrom (1902-1962), previously
a Yale mathematics professor, and William
C. Norris (1911-). The company was based in
8 - The Standards
Bureau Machines
The American National Bureau of
Standards (NBS) also became involved in early computer development. This came
about thanks to their prior interest in the production of mathematical tables -
experience which meant they had to work very closely with military research
units during the war. This cooperation continued after the war, and in 1947 the
Office of Naval Research sponsored the "National Applied Mathematics
Laboratories" (NAML) as the division of NBS responsible for advising
government agencies on computing issues. This brought with it a research
funding role, and resulted in two computer development projects. The first
contract went in October 1948 to the Institute for Numerical Analysis at the
BIOGRAPHICAL ASIDE - HARRY D. HUSKEY: [Compiled from a
number of Internet sources.] Harry D. Huskey (1916-) became involved in ENIAC
in 1944, when it was about half built, and worked on input and output devices
for the machine. When the ENIAC team started to split up, he accepted an
invitation from the UK to join the ACE project at the NPL [see Section 5],
where he was instrumental in initiating the construction of a test model. On
returning to the
BIOGRAPHICAL ASIDE - SAMUEL N. ALEXANDER: From the Charles
Babbage Institute website: "Alexander received his A.B. and B.S. from the
Due to the widely separated
geographical locations of the two development sites, the systems became known
as Standards Western Automatic Computer (SWAC) and Standards Eastern
Automatic Computer (SEAC) respectively. SWAC was a serial processing
machine fitted with 40 Williams-Kilburn electrostatic storage tubes, giving a
total memory capacity of 256 40-bit words. Backing storage was on an 8192 word
magnetic drum. The system remained in use until 1962. SEAC was basically an
EDVAC clone (Huskey, 1980), and thus a serial processing machine. Its memory
initially consisted of 3072 bytes of mercury delay line storage (Kirsch, 2003
online). Being a simpler design, and prioritised as a stop gap machine to
compensate for delays on the UNIVAC project, it was ready earlier than SWAC,
going operational in May 1950 (Ibid.). Urban (2001/2003 online)
offers some informative and entertaining reminiscences.
9 - The Whirlwind
Project
At MIT, meanwhile, their summer
school delegates had gone straight to work on a machine called "Whirlwind".
This work was carried out under the aegis of Professor Gordon S. Brown
(1907-1996), then the world authority on the theory of servomechanisms (see,
for example, Brown and Campbell, 1948), whose Servomechanisms Laboratory had
already spent the war years on the sort of analog computation, power-assisted,
fire control mechanisms which had transformed the fire control industry from
ready reckoner to lethal science. The sponsor, once again, was the Office of
Naval Research.
Now it so happened that one of
Brown's 1944 projects had been the US Navy's ASCA flight simulation system.
This was being developed to an analog computer specification, with the recently
graduated Jay
Wright Forrester (1918-) in charge of the computing aspects, and, by a
fortunate coincidence, Forrester had on his team a young engineer named Perry
Crawford. Crawford had written his master's thesis on the topic of digital
fire control systems, and according to Forrester himself was the person who
first called his attention to the possibility of digital computation. Forrester
accordingly proposed that Whirlwind should do the ASCA processing digitally,
rather than electromechanically, and work began against the revised digital
specification in early 1946. It then continued as a series of incremental
developments until a system was ready for acceptance trials in early 1950. The
initial specification was for a ten-ton machine offering 32 different op codes.
The Williams-Kilburn Tube (see next section but one) was for rapid access
memory until that technology was replaced in 1953. Gordon Welchman, late of
The Whirlwind project is rightly
famous for having introduced ferrite core RAM, and for promoting the use of
subroutines. The ferrite story began in 1949, when a Harvard researcher named
An Wang (1920-1990) developed the ferrite toroid single bit flip-flop,
and continued in 1951 when an MIT researcher used these units to build a
workable "core memory" .....
Critical Invention - The Ferrite
Toroid (1949) and Ferrite Core Memory (1951): Wang's invention
was a tiny ferrite toroid. Ferrite is a clay-iron oxide mix, baked as a ceramic.
It therefore has good magnetic properties. Before firing, the mixture can
readily be pressed into shape. A toroid is the technical name for the shape of
a doughnut, so it has a central hole through which a thin wire can be passed.
The passage of a current through the wire will then affect the magnetic state
of the ferrite, and the magnetic state of the ferrite will affect the passing
current. This therefore offered a conceptually neat way of linking two
electrical states (On/Off) with two magnetic states (On/Off), or, to put it
another way, of storing electrical pulses in ferrite on demand, and retrieving
them as electrical pulses when needed. Wang filed for a patent on 21st October
1949 (granted 17th May 1955), but his invention fell short of RAM as we know it
today, largely because Wang himself did not fully realise the implications of
what he had done. This required a second advance, namely of wiring the ferrite
toroids from two directions at once, that is to say, of passing two wires
through each toroid so that they ended up strung together like the knots
("nodes") on a fishing net. The technique was developed by MIT's
Whirlwind team in 1951, and a matrix of 16,384 toroids was fitted to the
Whirlwind in August 1953 [for a picture, click
here]. The technology remained in use until the mid-1970s,
when integrated circuits allowed much greater miniaturisation.
Waldrop (2001) points out that
Whirlwind was not designed for calculating per se. It was built as an
electronic flight simulator, "a machine for which there was never an
'answer', just a constantly changing sequence of pilot actions and simulated
aircraft responses" (p73). In consequence, the machine rates as the first
major real-time digital computer. Forrester subsequently spent a number of
years networking a large number of Whirlwind clones into a giant command and
control system known as SAGE,
which effectively was
10 - The IBM SSEC
The Selective Sequence Electronic
Calculator (SSEC) was IBM's first in-house digital computing project, and it
owes much of its success to the fact that it was conceived in a moment of
anger. Pugh (1984) suggests that IBM's Thomas J. Watson Sr was so deeply
angered by the lack of credit given to IBM during the development of the
Harvard Mark 1 that he authorised the follow-up project in-house. The project
began in March 1945, and was led by Wallace J. Eckert, originally a
11 - The
Some of the Bletchley Park team,
initially Newman, Good, and Rees, but eventually Turing himself, together with
some of the TRE people, notably Frederic (later Sir Frederic) Calland Williams
(1911-1977), Thomas ("Tom") Kilburn (1921-2001), and Geoff Tootill,
ended up after the war at Manchester University. Newman, Good, and Rees were
the first to arrive in around October 1945, and strengthened the Department of
Mathematics. Good and Rees were amongst the delegates to the 1946 Moore School
summer school, and, upon their return, the team sketched out the design for a
second British Turing machine (to complement Turing's own proposed Turing
machine at the NPL). Williams arrived in January 1947 as Professor of
"Electrotechnics", and Kilburn and Tootill (initially on secondment
from TRE) joined later. Using TRE surplus equipment, the team started to put
together a Small-Scale Experimental Machine - the SSEM, or "Baby".
ASIDE:
The main SSEM build took place
during 1947, and the machine ran its first program 21st June 1948. It contained
some 500 valves, could process seven different instructions, and could access
up to 1024 bits of randomly accessible information on what has come to be known
as a Williams-Kilburn [Cathode Ray] Tube .....
Key Development - Williams-Kilburn [Cathode
Ray] Tube: This was a cathode ray tube (CRT) (just like those
used in televisions), which made use of the one-second-or-so residual
electrostatic charge left on the screen following each passing of the electron
beam [for technical details, see the Manchester University website].
Appropriately equipped with sensors, CRTs could thus operate as fast
"random access" devices. The technology was subsequently used on the
IAS machine, the Manchester Mark 1, and the Whirlwind project (until it
developed ferrite core RAM in 1953), and can be described as fast but not
particularly reliable. Impressed by the speed factor as a marketing advantage
in their confrontation with Remington-Rand, IBM did much to improve the
reliability of CRT technology, and installed the technology in the highly
successful IBM701 series (see Part 4).
The Baby was the world's first
stored program machine (beating BINAC - see below - by nine months), and
Kilburn wrote the first program. Tootill's technical
notebook is now partly online, and shows some of the possible operations [page 28 is from
19th June 1948, and gives a particularly good idea of the sort of programming
involved]. The system was demonstrated to Sir Ben Lockspeiser, Chief Scientist
at the Ministry of Supply, in October 1948, and he was so impressed that
government funding was made available via Ferranti Limited for a scaled up
version (Lavington, 1980/2002 online). This
was known as the "Ferranti Mark 1".
ASIDE: There is some confusion in
the literature as to the evolutionary tree leading from SSEM to the Ferranti
Mark 1, especially when the name "Manchester Mark 1" is seen. If
interested in the exact line of inheritance, see the
Turing joined the Mathematics
Department as reader in 1948, whilst among the younger members of the
electrotechnics team were the Cwmamman-born Gordon Eric ("Tommy")
Thomas (1928-), the Pontypridd-born David B.G. ("Dai") Edwards
(1928-), Alec Robinson, Richard Grimsdale, and J.C. ("Cliff") West.
Tommy Thomas's website is full of informative fact and anecdote, and shows that
the Internet is no barrier to the properly trained old-timer.
The Mark 1 also had access to more
permanent storage on a magnetic drum.
Key Development - Magnetic Drum: This was
a non-ferrous cylinder, coated with magnetic medium, and rotated against a row
of magnetic read-write heads connected to the input-output controller. It could
thus be used a temporary storage for one or more rotations of the drum during
program execution, or as backing storage between programs. Drums were used on
the Manchester Mark 1, and the Whirlwind project (although again only until it
developed ferrite core RAM in 1953).
12 - The
A n = Add the number in storage location n into
the accumulator.
S n = Subtract the number in storage location n
from the accumulator.
H n = Transfer the number in storage location n
into the multiplier register.
V n = Multiply the number in storage location n
by the number in the multiplier register and add into the accumulator.
N n = Multiply the number in storage location n
by the number in the multiplier register and subtract from the accumulator.
T n = Transfer the contents of the accumulator
to storage location n and clear the accumulator.
U n = Transfer the contents of the accumulator
to storage location n and do not clear the accumulator.
C n = Collate the number in storage location n
with the number in the multiplier register, ie. add a '1' into the accumulator
in digital positions where both numbers have a '1', and a '0' in other digital
positions.
R 2 n-2 = Shift the number in the accumulator n
places to the right; ie multiply it by 2-n.
L 2 n-2 = Shift the number in the accumulator n
places to the left; ie multiply it by 2n.
E n = If the number in the accumulator is
greater than or equal to zero execute next the order which stands in storage
location n, otherwise proceed serially.
G n = If the number in the accumulator is less
than zero execute next the order which stands in storage location n, otherwise
proceed serially.
I n = Read the next row of holes on the tape and
place the resulting 5 digits in the least significant places of storage
location n.
O n = Print the character now set up on the
teletypewriter and replace it with the character represented by the five most
significant digits in storage location n.
F n = Place the five digits which represent the
character next to be printed by the teletypewriter in the five most significant
digits in storage location n.
X = Round off the number in the accumulator to
16 binary digits.
Y = Round off the number in the accumulator to
34 binary digits.
Z = stop the machine and ring the warning bell.
Wilkes and Renwick continue:
"Ordinary 5-hole punched tape of the kind
used in telegraphy is used for input. Each row of holes represents a 5-digit
binary number and the basic input operation is to transfer this number to the
store." (Wilkes and
Renwick, 1950/1982, p418.)
Wilkes is often credited with the
invention of "Assembly Code", the generic name for software
which translates human-readable instructions into machine instructions [more on
this in Part 4
(Section 3.2)]. EDSAC was replaced in 1957 by EDSAC II.
Here is an analysis of the EDSAC's
strengths and weaknesses, measured against the criteria of modernity discussed
so far .....
|
Electronic rather than Electromechanical |
Digital rather than Analog |
Binary rather than Decimal |
General Purpose Stored Program |
|
Yes |
Yes |
Yes |
Yes |
The EDSAC was also the prototype for
the Lyons Electronic Office ("LEO") series of production machines.
Aris (2000) begins this story in 1923, when J. Lyons and Company, tea merchants
and caterers, took on a
Simmons was joined in 1936 by David
Caminer (1915-), who by the late 1940s had risen to manager of the Systems
Research Office, "a forward-looking team, some twenty strong, considering
new systems approaches and new technologies" (Aris, 2000, p5), and it was
against this background of disciplined risk-taking that two of the company's
directors, Thomas R. Thompson (d.1972) and Oliver Standingford, went off on a
fact-finding tour of computing installations in the US. What they wanted to
know was whether the new breed of computers was going to replace punched card
tabulators, and what influence they were going to have on office automation.
They consulted with established experts such as Goldstine, and upon their
return prepared a computerisation proposal which would cost
The LEO 1 contained 5000 valves, and
used mercury delay line storage. It also used three buffered input channels,
and two buffered output channels, enabling large blocks of data to be read or
written at a time. In this way, the record for employee (n+1) would be on its
way into the machine while that for employee (n) was being processed and that
for employee (n-1) was on its way out of the machine. [For some of Pinkerton's
detailed reminiscences, click here;
for Caminer's, click here.
Later versions of the machine, LEO 2 and LEO 3, are described in Part 4. The last
British Telecom LEO 3-26 was withdrawn from service in 1980, a few weeks after
the present author joined them as a trainee systems analyst.]
13 - BINAC and
UNIVAC
Having resigned from the
In purely commercial terms, however,
BINAC was a disaster, coming in seriously over budget on what had been a
fixed-price contract. The eventually more successful Universal Automatic
Computer, or UNIVAC, development followed in 1948. This began life
as a one-off for the US Census Bureau, under a contract signed in September
1946, but again development costs soon began to exceed the agreed price of
$350,270, and in 1948 Eckert and Mauchly had no choice but to sell 40% of their
company to American Totalisator Company in return for an injection of capital.
A subsequent deal in November 1949 saw the company incorporated into the
Remington-Rand Corporation, who funded the rest of the development.
The basic binary code used 6
substantive bits, giving it a repertoire of 64 different characters. There was
also a seventh parity bit .....
Key Development - Parity Bit: Parity
bits are additional bits tagged on to the end of an otherwise already
meaningful bit sequence. They are set according to a mathematical algorithm,
and then regularly rechecked during processing. They are thus extremely
effective ways of detecting incipient equipment failure or file corruption.
UNIVAC delivered 2000 simple
additions per second from a 5400 valve system with 1000 84-bit words in mercury
delay line memory [pictures]. A
total of 46 machines were produced before the range was replaced by the UNIVAC
2 (see Part 4).
They were generally reliable and comparatively easy to program.
14 - Hardware
Summary Table, 1943-1950
The EDSAC, LEO 1, and UNIVAC are
convenient demarcation points between computing's formative years and the early
production years (covered in Part 4). Here is a
progress summary table for those formative years. The material contained is
from many sources, including
|
Name/ Claim to Fame |
Project Leader(s)/ Purpose |
Date/ Sponsor |
Remarks |
|
Relay Interpolator First use of biquinary notation for additional reliability |
Samuel Williams, George Stibitz Ballistics computation for the AA Predictor No. 9 (see Part 2). |
Started 1941 Operational September 1943 Decommissioned 1961 |
Also known as Bell Labs "Model 2 Relay Calculator". (The Model 1 was described at the end of Part 2.) |
|
The Bombe First series of |
Max Newman, Tommy Flowers, Alan Turing, C.E.
Wynn-Williams, Gordon Welchman, Jack Good (from 1941) Military code-breaking |
Started late 1939 Operational late 1941 |
Once the prototype had proven itself, several hundred further machines were built by 1945. |
|
The Robinsons First |
Max Newman, Tommy Flowers, Alan Turing, C.E.
Wynn-Williams, Gordon Welchman, Jack Good (from 1941), Shaun Wylie (from
1943) Military code-breaking |
Started 1942 Operational mid-1943 |
Valve-based experimental machines, soon replaced by the Colossus series (see below). |
|
Ballistic Computer |
Samuel Williams, George Stibitz Ballistics computation for the AA Predictor No. 9 (see Part 2). |
Started 1942 Operational June 1944 |
Also known as Bell Labs "Model 3 Relay Calculator". |
|
Colossus 1 First |
Max Newman, Tommy Flowers, Alan Turing, C.E.
Wynn-Williams, Gordon Welchman, Jack Good (from 1941), Donald Michie (from
1942) Military code-breaking |
Started January 1943 Operational December 1943 |
|
|
Colossus 2 First |
Max Newman, Tommy Flowers, Alan Turing, C.E. Wynn-Williams,
Gordon Welchman, Jack Good (from 1941), Donald Michie (from 1942), A.W.M.
Coombs Military code-breaking |
Started March 1944 Operational June 1944 |
A further nine machines were built by 1945. |
|
ASCC (or "Harvard Mark I") Largest ever electro-mechanical calculator; digital rather than analog |
Howard H. Aiken, Robert Campbell, Grace Hopper (from
1942) Ballistics computation and other important war work. |
Started 1937; operational January 1943 on-site at
IBM, August 1944 at Harvard; further development to 1947 (when replaced by
Mark 2 - see below); dismantled for museum use 1959. |
ASCC = Automatic Sequence-Controlled Calculator A work-horse, but not earth-shatteringly innovative. |
|
AA Predictor No. 9 Third generation analog flak predictor |
Samuel Williams |
Started Operational 1943 |
Very successful analog system. It would still be another decade before digital systems started to compete for battlefield computation. It did, however, make considerable use of digital equipment for testing purposes - see the entries for the Relay Interpolator and the Ballistic Computer above. |
|
Z4 First complete programming language PLANKALKÜL |
Konrad Zuse General purpose computing |
Started 1941 Completed 1946 Konrad Zuse personally |
|
|
Harvard Mark II First computer "bug" located 15th September 1945 by Grace Hopper (a moth jammed into one of the 13,000 or so component relays) |
Howard Aiken, Grace Hopper (until 1949), Edmund C. Berkeley, Frederick Miller |
Started 1942 Acceptance testing July 1947 Delivered January 1948 to the Naval Proving Ground, Harvard Computation Labs |
|
|
ENIAC First purely electronic computer |
John Brainerd, John Mauchly (until 1946), Presper
Eckert (ditto), Herman Goldstine, Arthur Burks, Thomas Sharpless, Robert Shaw Ballistics computation and other important war work. |
Started May 1943; operational February 1946;
delivered to the Aberdeen Proving Ground, MD, January 1947; recommissioned
August 1947; further development until October 1955. |
Eckert and Mauchly fell out with the |
|
General Purpose Relay Calculator Early self-checking system, and therefore comparatively reliable |
Bell Labs team, incl. George Stibitz and Samuel Williams |
Started 1944 Two-off, one operational July 1946 at the National
Advisory Committee for Aeronautics, Langley Field, VA, and the other February
1947 at the US Army's Ballistic Research Labs, |
Also known as Bell Labs "Model 5 Relay Computer". These machines cost roughly $500,000 each. |
|
Whirlwind 1 First use of ferrite core memory; first real time command and control applications |
Gordon Brown, Jay Forrester, Robert Everett, Perry Crawford,
William Papian, Harlan Anderson (from 1952), Ken Olsen, Jack Gilmore (from
1950), Charles Adams, John Carr, Gordon Welchman (from 1948 to 1951) Gunnery fire control; real-time simulation |
Started 1944 as an analog flight simulator project;
respecified for digital computation late 1945-early 1946; operational June
1950; fitted with 16kb ferrite core store August 1953 (enough for 1024 16-bit
words). MIT, for the |
Anderson and Olsen left in 1957 to found the Digital
Equipment Corporation (DEC) [for a fuller story, click here]. Welchman had
been one of the |
|
EDVAC First |
|
Scoping meeting August 1944; design draft 1945; build
started 1946, but subject to repeated design upgrades as problems were solved
and new techniques developed; assembled and delivered while still
non-operational August 1949; ran first program November 1951; operational
April 1952; decommissioned December 1962. Moore School of Electrical Engineering, University of Pennsylvania, for the Ballistics Research Laboratory, Aberdeen Proving Ground, MD. |
EDVAC = Electronic Discrete Variable Automatic
Computer. This was not a particularly well managed project. ORDVAC (see Part 4) started many months later and nearly beat it into service. |
|
IAS Early US stored program machine |
John Von Neumann, Herman Goldstine, Julian Bigelow
(from January 1946); Willis Ware (until 1952); John Tukey; Ralph Slutz Click here for the story of Bigelow's dog! |
Started March 1946 Operational Spring 1952 Institute for Advanced Study, |
The IAS was to all intents and purposes a research machine. It had no fixed delivery date, and was constantly being tinkered with as new ideas - some good, some bad - came and went. Thus although development began before EDSAC the machine did not become operational until after it. Eventually, however, it would spin off a number of major clones. |
|
Pilot ACE Fastest ever processor at the time, with a separate module for parallel computation of multiplications and divisions. |
John Womersley, Alan Turing (until 1948), Jim Wilkinson (from May 1946), Edward A. Newman; G.G. Allway; Harry Huskey (from January 1947), Michael Woodger, Robin Gandy, Donald Davies (from September 1947) |
Specification work 1946; development 1949; pilot operations
April 1950, then constantly improved until discarded 1958 in favour of the
full ACE (see Part
4). National Physical Laboratory |
Huskey, an American on placement, returned to the |
|
IBM SSEC First IBM in-house electronic digital computer. |
Wallace Eckert, R. Seeber, Frank Hamilton, Wayne Brooke |
Started March 1945; acceptance testing late 1947; operational
January 1948; decommissioned August 1952 IBM |
SSEC = Selective Sequence Electronic Calculator |
|
Baby First stored program; Williams tube storage. |
Frederick Williams, Tom Kilburn, Alec Robinson, Geoff
Tootill research prototype |
Started 1947 Operational 21st June 1948 |
Williams and Kilburn had worked together since 1942
on a number of military electronics projects. They moved to |
|
Harvard Mark III First major use of magnetic drum memory. |
Howard Aiken, Grace Hopper (until 1949), Edmund C. Berkeley, An Wang (between 1948 and 1951), Frederick Miller |
Started 1947 Operational March 1951 Harvard Computation Labs for the |
An Wang patented the ferrite toroid (see main text) in 1949, left to found his own company, Wang Labs, in 1951, and from 1965 was a major force in the pocket calculator market. |
|
First large-scale von Neumann computer; first Williams-Kilburn tube random access memory; first magnetic drum store; development prototype for Ferranti Mark 1 production series |
Frederick Williams, Tom Kilburn, Alan Turing (from September 1948), Geoff Tootill (until January 1949), Alick Glennie, Jack Good (until 1948), David Rees (until 1949), P.M.S.Blackett, David Edwards (from October 1948), Tommy Thomas (same), Alec Robinson, Cliff West; Andrew Booth |
Started 1948; Pilot Operations April 1949; Fully
operational October 1949; Replaced February 1951 by a Ferranti Mark 1 |
Geoff Tootill left for Ferranti after the Baby had
been born, and established close liaison between that company and |
|
EDSAC First full-sized stored program computer; first bootstrap (fast start) routine; first subroutines and reusable code; development prototype for J. Lyons and Company's LEO production series. |
Maurice Wilkes, David Wheeler, W. Renwick, S. Barton, G. Stevens, Stan Gill (from 1949) |
Started 1947; operational May 1949; further
development until 1953; decommissioned July 1958, when replaced by EDSAC II |
EDSAC = Electronic Delay Storage Automatic
Calculator The team subsequently published many of their ideas in the first textbook of programming, "The Preparation of Programs for an Electronic Digital Computer" (Wilkes, Wheeler, and Gill, 1951). |
|
MOSAIC Early British use of valve-transistor mix. |
Dollis Hill engineers under A.W.M. Coombs |
Started 1947 Operational 1954 Dollis Hill, for the Ministry of Supply |
|
|
BINAC First twinned processor for greater reliability; early
use of magnetic tape rather than punched cards; first |
Eckert and Mauchly |
Started October 1947 Program Testing March 1949 Pilot operations August 1949 Delivered September 1949 Eckert-Mauchly Computer Corporation, |
BINAC = Binary Automatic Computer. In purely commercial terms, this was little short of a disaster, forcing Eckert and Mauchly to sell control of their company to the Remington-Rand Corporation. |
|
Harvard Mark IV |
Howard Aiken, Grace Hopper (until 1949), Edmund C.
Berkeley, An Wang (between 1948 and 1951), |
Delivered 1952 Harvard Computation Labs |
Iverson subsequently developed the APL programming language. |
|
LEO 1 Early use of buffered I/O channels; early |
John Pinkerton, Ernest Lanaerts, David Caminer General purpose commercial computing |
Started 1949 Completed 1953 J. Lyons and Co Ltd |
LEO = |
|
SEAC Probably the first |
Sam Alexander |
Operational May 1950 US Bureau of Standards, |
SEAC = Standards' Eastern Automatic Computer |
|
SWAC |
Harry Huskey |
US Bureau of Standards, |
SWAC = Standards' Western Automatic Computer |
|
UNIVAC 1 First use of magnetic tape as long-term storage; first stores system project (on the USAF machine from 1952); first payroll project (on the General Electric machine from 1953). |
John Mauchly and Presper Eckert, Grace Hopper (from
1949) General Purpose Computing |
Started 1948 Operational March 1951 Initially Eckert-Mauchly Computer Corporation, |
UNIVAC = Universal Automatic Computer. Eckert and Mauchly's company was bought out by Remington-Rand in 1950. A total of 46 machines were eventually built, selling at around $1M each. |
15 - References