Subject: A Chronology of Digital Computing to 1952 (improved version)
From: [email-masked] (Mark Brader)
Newsgroups: comp.misc,alt.folklore.computers

Alt.folklore.computers readers have seen this article reposted
periodically; it appeared originally in comp.misc.  As I have
just completed this new and substantially more detailed version
of it (for which I owe a debt of gratitude to Michael Williams
for supplying me with a copy of his book), I have decided to
post it to both newsgroups now.  Followups to a.f.c.

     ----------------------------------------------------

What was the first computer and who built it?

It turns out that this is more a question of definition than a
question of fact.  The computer, as we now understand the word,
was very much an evolutionary development rather than a simple
invention.  This article traces the sequence of the most important
steps in that development, and in the earlier development of
digital calculators without programmability.  It may help you
to decide for yourself whether you think the first computer was
the ABC, the V3 (aka Z3), the ENIAC, the SSEC, the Manchester
Mark I, the EDSAC, or perhaps yet another machine -- and how to
apportion the honor of invention among John Atanasoff, Charles
Babbage, Presper Eckert, John Mauchly, Alan Turing, John von
Neumann, Konrad Zuse, and others.

     ----------------------------------------------------

This article has evolved from an original version that I drafted
in 1988, and has been posted to various Usenet groups several times.
It has been prepared primarily from two sources:

        Bit by Bit: An Illustrated History of Computers
        by Stan Augarten
        1984, Ticknor and Fields, New York
        ISBN 0-89919-268-8, 0-89919-302-1 paperback

        A History of Computing Technology
        by Michael R. Williams
        1985, Prentice-Hall, Englewood Cliffs, NJ
        ISBN 0-13-389917-9

Either of these books is well worth a trip to the library to read.
(Unfortunately, finding either one in a bookstore today would be an
unlikely proposition.)  Augarten is a journalist; he writes very
readably, but occasionally does not say exactly what he means.
Williams is a computer science professor; his book is superior in
technical depth, and covers additional subject areas including
analog computing and computing in ancient times.

For some material in the last part of the chronology I also
consulted:

        Encyclopedia of Computer Science and Engineering, 2nd ed.
        editor Anthony Ralston, associate Editor Edwin D. Reilly Jr.
        1983, Van Nostrand Reinhold, New York
	ISBN 0-442-24496-7

	Portraits in Silicon
	by Robert Slater
	1987, MIT Press, Cambridge, MA
	ISBN 0-262-69131-0

	The Computer Comes of Age / Ainsi naquit l'informatique
	by R. Moreau, English translation by J. Howlett
	1981, translated 1984, MIT Press, Cambridge, MA
	ISBN 0-262-36103-2

The August 1988 issue of Scientific American contained a article
about the Atanasoff-Berry machines.  There is also a book by Clark
Mollenhoff about them, some information from which was forwarded to
me by email.  The February 1993 issue of Scientific American
contained an article about Babbage's difference engines and the
modern-day completion of one of them.  

     ----------------------------------------------------

I've tried to mention in this chronology each machine within the
relevant time period that meets the following criteria.  First,
it must do arithmetic digitally; this eliminates, for instance,
the slide rule.  Second, it must actually do the arithmetic rather
than just assisting the user's memory; I consider this to eliminate
the abacus as well as, say, Napier's Bones.  Third, it must do
essentially the whole computation, with little or no assistance
from the user; you could subtract 16 on a 6-digit Pascaline by
adding 999984, but this doesn't mean we should say that a Pascaline
could subtract.

And finally, the machine must have either been technologically
innovative, or else well known and influential.  For certain concepts
of special importance, I have also listed the first time they were
*described*, although they were not implemented at that time.

Where I do not describe the size of a machine, it is generally
suitable for desktop use if it has no memory and is unprogrammable
or if it is a small prototype, but would fill a small room if it has
memory or significant programmability.

The term "full-scale" is used, in contrast to "prototype", to refer
to a machine with sufficient capacity to do regular useful work.
For the sorts of machines described toward the end of the chronology,
I generally consider them "completed" when they first run a program,
even though they may be subject to further modifications and debugging.

The names Tuebingen, Wuerttemberg, and Mueller should have an
umlauted "u" in place of the "ue" used in this ASCII text.

     ----------------------------------------------------
     A Chronology of Digital Computing Machines (to 1952)
     ----------------------------------------------------

1623.	Wilhelm Schickard (1592-1635), of Tuebingen, Wuerttemberg
	(now in Germany), makes his "Calculating Clock".  This is a
6-digit machine that can add and subtract, and indicates overflow
by ringing a bell.  Mounted on the machine is a set of Napier's Rods
(or Bones), a memory aid facilitating multiplications.  The machine
and plans are lost and forgotten in the war that is going on.

The plans are finally rediscovered in 1935, only to be lost in war
again, and then re-rediscovered in 1956 by the same man!  The machine
is reconstructed in 1960, and found to be workable.

(Schickard is a friend of the astronomer Kepler.)

1644-5.	Blaise Pascal (1623-1662), of Paris, makes his "Pascaline".
	This 5-digit machine uses a different carry mechanism from
Schickard's, with rising and falling weights instead of a direct
gear drive; it can be extended better to support more digits, but
it cannot subtract, and probably is less reliable than Schickard's
simpler method.

Where Schickard's machine is forgotten -- and indeed Pascal is
apparently unaware it ever existed -- Pascal's becomes well known
and establishes the computing machine concept in the intellectual
community.  He makes more machines and sells about 10-15 of them,
some supporting as many as 8 digits.  (Several survive to the
present day.)  Patents being a thing of the future, others also
sell copies of Pascal's machine.

(Pascal is also the inventor of the bus.)

c.1668.	Sir Samuel Morland (1625-1695), of England, produces a
	non-decimal adding machine, suitable for use with English
money.  Instead of a carry mechanism, it registers carries on
auxiliary dials, from which the user must reenter them as addends.

1674.	Gottfried Wilhelm von Leibniz (1646-1716), of Leipzig,
	designs his "Stepped Reckoner", which is constructed by a
man named Olivier, of Paris.  It uses a movable carriage so that it
can multiply, with operands of up to 5 and 12 digits and a product
of up to 16.  The user has to turn a crank once for each unit in
each digit in the multiplier; a fluted drum translates the turns
into additions.  But the carry mechanism requires user intervention,
and doesn't really work in all cases anyway.

Leibniz's machine doesn't get forgotten, but it does get misplaced
in an attic within a few years -- and stays there until 1879 when
it is noticed by a man working on the leaky roof!

(Leibniz, or Leibnitz, is also the co-inventor of calculus.)

1775.	Charles, the third Earl Stanhope, of England, makes a
	successful multiplying calculator similar to Leibniz's.

1770-6.	Mathieus Hahn, somewhere in what is now Germany, also makes
	a successful multiplying calculator.

1786.	J. H. Mueller, of the Hessian army, conceives the idea of
	what came to be called a "difference engine".  That's a
special-purpose calculator for tabulating values of a polynomial,
given the differences between certain values so that the polynomial
is uniquely specified; it's useful for any function that can be
approximated by a polynomial over suitable intervals.  Mueller's
attempt to raise funds fails and the project is forgotten.

1820.	Charles Xavier Thomas de Colmar (1785-1870), of France,
	makes his "Arithmometer", the first mass-produced calculator.
It does multiplication using the same general approach as Leibniz's
calculator; with assistance from the user it can also do division.
Machines of this general design, large enough to occupy most of a
desktop, continue to be sold for about 90 years.

1822.	Charles Babbage (1792-1871), of London, having reinvented
	the difference engine, begins his (government-funded)
project to build one by constructing a 6-digit calculator using
gear technology similar to that planned for the difference engine.

1832.	Babbage and Joseph Clement produce a prototype segment of
	his difference engine, which operates on 6-digit numbers
and 2nd-order differences (i.e. can tabulate quadratic polynomials).

The complete engine, which would be room-sized, is planned to be
able to operate both on 6th-order differences with numbers of about
20 digits, and on 3rd-order differences with numbers of 30 digits.
Each addition would be done in two phases, the second one taking
care of any carries generated in the first.  The output digits
would be punched into a soft metal plate, from which a plate for a
printing press could be made.

But there are various difficulties, and no more than this prototype
piece is ever assembled.

1834.	George Scheutz, of Stockholm, produces a small difference
	engine in wood, after reading a brief description of
Babbage's project.

1834.	Babbage conceives, and begins to design, his "Analytical
	Engine".  Whether or not this machine, if built, would
have constituted a computer depends on exactly how "computer" is
being defined.  One essential feature of present-day computers
is absent from the design: the "stored-program" concept, which is
necessary for implementing a compiler.  The program would have
been in read-only memory, specifically in the form of punch cards.
(In this chronology, such machines will be called "programmable
calculators".)

Babbage continues to work on the design for years, though after
about 1840 the changes are minor.  The machine would operate on
40-digit numbers; the "mill" (CPU) would have 2 main accumulators
and some auxiliary ones for specific purposes, while the "store"
(memory) would hold perhaps 100 more numbers.  There would be
several punch card readers, for both programs and data; the cards
would be chained and the motion of each chain could be reversed.
The machine would be able to perform conditional jumps.  There
would also be a form of microcoding: the meaning of instructions
would depends on the positioning of metal studs in a slotted
barrel, called the "control barrel".

The machine would do an addition in 3 seconds and a multiplication
or division in 2-4 minutes.

1842.	Babbage's difference engine project is officially canceled.
	(The cost overruns have been considerable, and Babbage is
spending too much time on redesigning the Analytical Engine.)

1843.	Scheutz and his son Edvard Scheutz produce a 3rd-order
	difference engine with printer, and the Swedish government
agrees to fund their next development.

1847-9.	Babbage designs an improved, simpler difference engine,
	which will operate on 7th-order differences and 31-digit
numbers, but nobody is interested in paying to have it built.

(In 1989-91, however, a team at London's Science Museum will do
just that.  They will use components of modern construction, but
with tolerances no better than Clement could have provided... and,
after a bit of tinkering and detail-debugging, they will find that
the machine does indeed work.)

1853.	To Babbage's delight, the Scheutzes complete the first
	full-scale difference engine, which they call a Tabul-
ating Machine.  It operates on 15-digit numbers and 4th-order
differences, and produces printed output as Babbage's would have.
A second machine is later built to the same design by the firm
of Brian Donkin of London.

1858.	The first Tabulating Machine is bought by the Dudley
	Observatory in Albany, New York, and the second one by
the British government.  The Albany machine is used to produce
a set of astronomical tables; but the observatory's director is
then fired for this extravagant purchase, and the machine is
never seriously used again, eventually ending up in a museum.
The second machine, however, has a long and useful life.

1871.	Babbage produces a prototype section of the Analytical
	Engine's mill and printer.

1878.	Ramon Verea, living in New York City, invents a calculator
	with an internal multiplication table; this is much faster
than the shifting carriage or other digital methods.  He isn't
interested in putting it into production; he just wants to show that
a Spaniard can invent as well as an American.

1879.	A committee investigates the feasibility of completing the
	Analytical Engine and concludes that it is impossible now
that Babbage is dead.  The project is then largely forgotten and is
unknown to most of the people mentioned in the last part of this
chronology -- though Howard Aiken is an exception.

1885.	A multiplying calculator more compact than the Arithmometer
	enters mass production.  The design is the independent, and
more or less simultaneous, invention of Frank S. Baldwin, of the
United States, and T. Odhner, a Swede living in Russia.  The fluted
drums are replaced by a "variable-toothed gear" design: a disk with
radial pegs that can be made to protrude or retract from it.

1886.	Dorr E. Felt (1862-1930), of Chicago, makes his "Comptometer".
	This is the first calculator where the operands are entered
merely by pressing keys rather than having to be, for example, dialed
in.  It is feasible because of Felt's invention of a carry mechanism
fact enough to act while the keys return from being pressed.

1889.	Felt invents the first printing desk calculator.

1890.	US Census results are tabulated for the first time with sig-
	nificant mechanical aid: the punch card tabulators of Herman
Hollerith (1860-1929) of MIT, Cambridge, Mass.  This is the start of
the punch card industry.  The cost of the census tabulation is 98%
*higher* than the previous one, in part because of the temptation to
use the machines to the fullest and tabulate more data than formerly
possible, but the tabulation is completed in a much shorter time.
Another precedent is that the cards are read electrically.

(Contrary to popular impression and to earlier versions of this
chronology, Hollerith's cards of 1890 are not the same size as
US paper money of the time; they are much smaller.  Other sizes of
punch cards will also appear within a few years.)

1892.	William S. Burroughs (1857-1898), of St. Louis, invents a
	machine similar to Felt's but more robust, and this is the
one that really starts the office calculator industry.

(This machine is still hand powered, but it won't be many years
before electric calculators appear.)

1906.	Henry Babbage, Charles's son, with the help of the firm of
	R. W. Munro, completes the mill of his father's Analytical
Engine, just to show that it would have worked.  It does.  The
complete machine is never produced.

1919.	W. H. Eccles and F. W. Jordan publish the first flip-flop
	circuit design.

1931-2. E. Wynn-Williams, at Cambridge, England, uses thyratron
	vacuum tubes to construct a binary digital counter for use
in connection with physics experiments.

1935.	International Business Machines introduces the "IBM 601",
	a punch card machine with an arithmetic unit based on relays
and capable of doing a multiplication in 1 second.  The machine
becomes important both in scientific and commercial computation,
and about 1500 of them are eventually made.

1937.	George Stibitz (c.1910-) of the Bell Telephone Laboratories
	(Bell Labs), New York City, constructs a demonstration 1-bit
binary adder using relays.

1937.	Alan M. Turing (1912-1954), of Cambridge University, England,
	publishes a paper on "computable numbers".  This paper solves
a mathematical problem, but the solution is achieved by reasoning
(as a mathematical device) about the theoretical simplified computer
known today as a Turing machine.

1938.	Claude E. Shannon (c.1918-) publishes a paper on the
	implementation of symbolic logic using relays.

1938.	Konrad Zuse (1910-) of Berlin, with some assistance from
	Helmut Schreyer, completes a prototype mechanical binary
programmable calculator, originally called the "V1" but retroactively
renamed "Z1" after the war.  It works with floating point numbers
having a 7-bit exponent, 16-bit mantissa, and a sign bit.  The
memory uses sliding metal parts to store 16 such numbers, and works
well; but the arithmetic unit is less successful.

The program is read from punched tape -- not paper tape, but
discarded 35 mm movie film.  Data values can be entered from a
numeric keyboard, and outputs are displayed on electric lamps.

Nov 1939. John V. Atanasoff (1903-) and graduate student Clifford
	Berry (?-1963), of Iowa State College (now the University
of Iowa), Ames, Iowa, complete a prototype 16-bit adder.  This is
the first machine to calculate using vacuum tubes.

1939.	Zuse and Schreyer begin work on the "V2" (later "Z2"),
	which will marry the Z1's existing mechanical memory unit to
a new arithmetic unit using relay logic.  The project is interrupted
for a year when Zuse is drafted.

(Zuse is a friend of Wernher von Braun, who will later develop the
*other* "V2", and after that, play a key role in the US space program.)

1939/40. Schreyer completes a prototype 10-bit adder using vacuum
	tubes, and a prototype memory using neon lamps.

Jan 1940. At Bell Labs, Samuel Williams and Stibitz complete a
	calculator which can operate on complex numbers, and give
it the imaginative name of the "Complex Number Calculator"; it is
later known as the "Model I Relay Calculator".  It uses telephone
switching parts for logic: 450 relays and 10 crossbar switches.
Numbers are represented in "plus 3 BCD"; that is, for each decimal
digit, 0 is represented by binary 0011, 1 by 0100, and so on up to
1100 for 9; this scheme requires fewer relays than straight BCD.

Rather than requiring users to come to the machine to use it, the
calculator is provided with three remote keyboards, at various
places in the building, in the form of teletypes.  Only one can be
used at a time, and the output is automatically displayed on the
same one.  In September 1940, a teletype is set up at a mathematical
conference in Hanover, New Hampshire, with a connection to New York,
and those attending the conference can use the machine remotely.

1940.	Zuse is released from the army and completes the Z2.
	It works better than the Z1, but isn't reliable enough.
(Later he is drafted again, and released again.)

Summer 1941. Atanasoff and Berry complete a special-purpose calcu-
	lator for solving systems of simultaneous linear equations,
later called the "ABC" ("Atanasoff-Berry Computer").  This has 60
50-bit words of memory in the form of capacitors (with refresh
circuits -- the first regenerative memory) mounted on two revolving
drums.  The clock speed is 60 Hz, and an addition takes 1 second.

For secondary memory it uses punch cards, moved around by the user.
The holes are not actually punched in the cards, but burned.  The
punch card system's error rate is never reduced beyond 0.001%, and
this isn't really good enough.

(Atanasoff will leave Iowa State after the US enters the war, and
this will end his work on digital computing machines.)

Dec 1941. Now working with limited backing from the DVL (German Aero-
	nautical Research Institute), Zuse completes the "V3" (later
"Z3"): the first operational programmable calculator.  It works with
floating point numbers having a 7-bit exponent, 14-bit mantissa
(with a "1" bit automatically prefixed unless the number is 0),
and a sign bit.  The memory holds 64 of these words and therefore
requires over 1400 relays; there are 1200 more in the arithmetic
and control units.

The program, input, and output are implemented as described above for
the Z1.  Conditional jumps are not available.  The machine can do 3-4
additions per second, and takes 3-5 seconds for a multiplication.
It is a marginal decision whether to call the Z3 a prototype; with
its small memory it is certainly not very useful on the equation-
solving problems that the DVL was mostly interested in.

Jan 1943. Howard H. Aiken (1900-1973) and his team at Harvard
	University, Cambridge, Mass. (with IBM's backing), complete
the "ASCC Mark I" ("Automatic Sequence-Controlled Calculator Mark I"),
also called the "Harvard Mark I".  This electromechanical machine is
the first programmable calculator to be widely known:  Aiken is to
Zuse as Pascal to Schickard.

The machine is 51 feet long, weighs 5 tons, and incorporates 750,000
parts.  It includes 72 accumulators, each incorporating its own arith-
metic unit as well as a mechanical register with a capacity of 23
digits plus sign.  (See the ENIAC entry, below, for a more detailed
description of such an architecture.)  The arithmetic is fixed-point,
with a plugboard setting determining the number of decimal places.
I/O facilities include card readers, a card punch, paper tape readers,
and typewriters.  There are 60 sets of rotary switches, each of which
can be used as a constant register -- sort of a mechanical read-only
memory.

The program is read from one paper tape; data can be read from the
other tapes, or the card readers, or from the constant registers.

Conditional jumps are not available.  However, in later years the
machine is modified to support multiple paper tape readers for the
program, with the transfer from one to another being conditional,
sort of like a conditional subroutine call.  Another addition allows
the provision of plugboard-wired subroutines callable from the tape.

Apr 1943. Max Newman, Wynn-Williams, and their team at Bletchley Park,
	a secret side near Cambridge, England, complete the "Heath
Robinson".  This is a special-purpose machine for cipher-breaking,
not a general-purpose calculator or computer but some sort of logic
device, using a combination of electronics and relay logic.  It reads
data optically at 2000 characters per second from 2 closed loops
of paper tape, each typically about 1000 characters long.

(The secrecy that surrounded this machine and its successors at
Bletchley Park will still be partially in effect at the time of
writing, hence the vague description.  Newman knew Turing from
Cambridge, and had been the first person to see a draft of Turing's
1937 paper.  Heath Robinson is the name of a British cartoonist known
for drawings of comical machines, like the American Rube Goldberg.
Two later machines in the series will be named for London stores
with "Robinson" in their names!)

Sep 1943. Williams and Stibitz complete the "Relay Interpolator",
	later called the "Model II Relay Calculator".  This is a
programmable calculator; again, the program and data are read from
paper tapes.  An innovative feature is that, for greater reliability,
numbers are represented in a biquinary format using 7 relays for
each digit, of which exactly 2 should be "on": 01 00001 for 0,
01 00010 for 1, and so on up to 10 10000 for 9.

(Some of the later machines in this series used the biquinary
notation for the digits of floating-point numbers.)

Dec 1943. H. T. Flowers and his team at Bletchley Park complete the
	the first "Colossus".  This successor to the "Robinson"
series machines is entirely electronic, incorporating 2400 vacuum
tubes for logic.  It has 5 paper tape loop readers, each working
at 5000 characters per second.

(10 Colossi were eventually built.  Turing also had an important
role at Bletchley Park, but did not work directly on the machines.)

1944-5.	Zuse almost completes his first full-scale machine, the "V4"
	(later "Z4"), which resembles his earlier designs.  Its
memory reverts to the Z1's mechanical design, storing 1000 words of
32 bits in less then a cubic meter; the equivalent in relays would
have filled a large room.

As the war begins to go very badly for Germany, Zuse's work is dis-
rupted several times, and then abandoned for the duration.  An air
raid had destroyed the Z3 in 1943, but the incomplete Z4 survives the
war's end in a basement.

1945.	Zuse invents a programming language called Plankalkul.

Jun 1945. John von Neumann (1903-1957) joins the ENIAC team and
	drafts a report describing the future computer eventually
built as the "EDVAC" ("Electronic Discrete Variable Automatic
Computer" (!)); this is the first description of the design of a
stored-program computer, and gives rise to the term "von Neumann
computer".

The first draft of the report fails to credit other team members
such as Eckert and Mauchly; when this version becomes widely
circulated, von Neumann gets somewhat too much credit for the
design.  The final version corrects the oversight, but too late.

(Von Neumann, also noted for his mental calculating ability, is
the only one of the principal computer pioneers in the US familiar
with Turing's 1937 paper.)

Nov 1945. John W. Mauchly (pronounced Mawkly; 1907-80) and J. Presper
	Eckert (1919-) and their team at the Moore School of Electrical
Engineering, of the University of Pennsylvania, Philadelphia, complete
a secret project for the US Army's Ballistics Research Lab: a program-
mable calculator called the "ENIAC" ("Electronic Numerator, Integrator,
Analyzer, and Computer").

The ENIAC's architecture resembles that of the Harvard Mark I, but
its components are entirely electronic, incorporating 17,468 vacuum
tubes.  The machine weighs 30 tons, covers about 1000 square feet
of floor, and consumes 130 or 140 kilowatts of electricity.

The machine incorporates 20 accumulators (the original plan was for 4).
The accumulators and other units are all connected by several data
buses, and a set of "program lines" for synchronization.  Each accum-
ulator stores a 10-digit number, using 10 bits to represent each digit,
and also incorporates circuits to add a number from a bus to the
stored number, and to transmit the stored number or its complement to
a bus.

A separate unit can perform multiplication (in about 3 milliseconds),
while another does division and square roots; the inputs and outputs
for both these units use the buses.  There are constant registers, as
on the Harvard Mark I: 104 12-digit registers forming an array called
the "function table".  100 of these registers are directly addressable
by a 2-digit number from a bus (the others are used for interpolations).
Finally, a card reader is available to input data values, and there
is a card punch for output.

The program is set up on a plugboard -- this is considered reasonable
since the same or similar program would generally be used for weeks
at a time.  For example, connecting certain sockets would cause
accumulator 1 to transmit its contents onto data bus 1 when a pulse
arrived on program line 1; meanwhile several accumulators could be
adding the value from that data bus to their stored value, while
others could be working independently.  The program lines are pulsed
under the control of a master unit, which can perform iterations.

The ENIAC's clock speed is 100 kHz.

Mauchly and Eckert apply for a patent.  The university disputes this
at first, but they settle.  The patent is finally granted in 1964,
but is overturned in 1973, in part because of the previous work by
Atanasoff, with which Mauchly was acquainted.

(The BRL wanted the ENIAC to use on the difficult problem of making
aiming tables for use by artillerymen.  It isn't ready in time for
the war, and overruns its original budget by 225% -- problems that
will face Eckert and Mauchly again on later projects.)

Feb 1946. The ENIAC is revealed to the public.

Jul-Aug 1946. The Moore School gives a course on "Theory and Techniques
	for Design of Electronic Computers"; lectures are given by
Eckert, Mauchly, Stibitz, von Neumann, and Aiken among others.  The
course leads to several projects being started, among them the EDSAC.

Jul 1947. Aiken and his team complete the "Harvard Mark II", a large
	programmable calculator using relays both for its 50 floating-
point registers and for the arithmetic unit, 13,000 of them in all.

Sep 1947. A moth (?-1947) makes the mistake of flying into the Harvard
	Mark II.  A whimsical technician makes the logbook entry "first
actual case of bug being found", and annotates it by taping down the
remains of the moth.

(The term "bug" was of course already in use; that's why it's funny.)

1947.	Frederick Viehe (?-1960), of Los Angeles, applies for a patent
	on an invention which is to use magnetic core memory.

c.1947.	The magnetic drum memory is independently invented by several
	people, and the first examples are constructed.

(As noted below, some early machines will use drums as main memory
rather than secondary memory.)

Jan 1948. Wallace Eckert (1902-1971, no relation to Presper Eckert)
	of IBM, with his team, completes the "SSEC" ("Selective
Sequence Electronic Calculator").  This technological hybrid has
8 vacuum tube registers, 150 words of relay memory, and 66 paper
tape loops storing a total of 20,000 words.  The word size is
20 digits, stored in BCD in the registers.

As with the Harvard Mark I in its later form, the machine can be
switched to read instructions from any of the paper tapes.  There
is also some use of plugboards in its programming.  But it can
also cache some instructions in memory and read them from there;
thus, in effect, it can operate either as a stored-program computer
(with a very small program memory) or not.  Because it can do this,
IBM's point of view is that this is the first computer.

Jun 1948. Newman, F. C. Williams, and their team at Manchester Uni-
	versity, Manchester, England, complete a prototype machine,
the "Mark I" (also called the "Manchester Mark I").  This is the
first machine that everyone would call a computer, because it's the
first with a true stored-program capability.

It uses a new type of memory developed by F. C. Williams (possibly
after an original suggestion by Presper Eckert), which uses the
residual charges left on the screen of a CRT after the electron
beam has been fired at it.  (The bits are read by firing another
beam through them and reading the voltage at an electrode beyond
the screen.)  This is a little unreliable but is fast, and also
relatively cheap because it can use existing CRT designs; and it is
much more compact than any other memory then existing.  The Mark I's
main memory of 32 32-bit words occupies a single Williams tube.
(Other CRTs on the machine are less densely used: one contains only
an accumulator.)

The Mark I's programs are initially entered in binary on a keyboard,
and the output is read in binary from another CRT.  Later Turing
joins the team and devises a primitive form of assembly language,
one of several developed at about the same time in different places.

Sep 1948. The ENIAC is improved, using ideas from Richard F. Clipper of
	the BRL and Nicholas Metropolis of Los Alamos.  Each program line
is permanently wired for a different operation, and a new converter
unit allows them to be addressed by a program, the way the function
table can -- thus implementing, in effect, opcodes.  With this change,
the program can now be entered via the *function table*.

(This conversion will sometimes be described as making the ENIAC into a
stored-program computer, but the program memory is still read-only.
However, setting up a program now takes a matter of hours, rather than
days as before.)

Fall 1948. IBM introduces the "IBM 604", a programmable calculator
	and card punch using vacuum tubes.  It can read a card,
perform up to 60 arithmetic operations in 80 milliseconds, and punch
the results on the same card.  The programming is by plugboard.

All machines first mentioned in the chronology from here on are
stored-program computers.

1949-51. Jay W. Forrester and his team at MIT construct the
	"Whirlwind" for the US Navy's Office of Research and
Inventions.  The vague date is because its advance to full-time
operational status is gradual.  Its original form has 3300 tubes
and 8900 crystal diodes.  It occupies 2500 square feet of floor.
Its 2048 16-bit words of CRT memory use up $32,000 worth of tubes
each month.  There is also a graphical I/O device consisting of a
CRT (only one dot can be displayed at a time) and a light pen.
This allows the machine to be used for air traffic control.

The Whirlwind is the first computer designed for real-time work;
it can do 500,000 additions or 50,000 multiplications per second.

Spring 1949. Forrester conceives the idea of magnetic core memory as
	it is to become commonly used, with a grid of wires used to
address the cores.  The first practical form, in 1952-53, will replace
the Whirlwind's CRT memory and render obsolete all types of main
memory then existing.

April 1949. The Manchester Mark I, its main memory now upgraded to
	128 40-bit words (on two CRTs), acquires a secondary memory
in the form of a magnetic drum holding a further 1024 words.  Also
at about this time, two index registers are added to the machine.

May 1949.  Maurice Wilkes (1913-) and his team at Cambridge Uni-
	versity complete the "EDSAC" ("Electronic Delay Storage
Automatic Computer"), which is closely based on the EDVAC design
report from von Neumann's group -- Wilkes had attended the 1946
Moore School course.  The project is supported both financially
and with technical personnel from J. Lyons & Co. Ltd., a large
British firm in the food and restaurant business.

This is the first full-scale operational stored-program computer,
and is therefore the final candidate for the title of "the first
computer".

Its main memory is of a type that had existed for some years, but
had not been used for a computing machine: the "ultrasonic delay
line" memory.  It had been invented originally by William Shockley
of Bell Labs (also one of the co-inventors of the transistor, in
1948), and Eckert had made an improved version in connection with
radar systems.  It works by repeatedly converting from the usual
electrical data pulses to ultrasonic pulses directed along, typic-
ally, the length of a tank of mercury; on arrival at the other end,
the pulses are converted back to electrical form.  The memory must
be maintained at a particular temperature, and only the few bits
currently in electrical form are accessible.  In the EDSAC, 16 tanks
of mercury give a total of 256 35-bit words (or 512 17-bit words).

The clock speed of the EDSAC is 500 kHz; most instructions take
about 1500 ms to execute.  Its I/O is by paper tape, and a set of
constant registers is provided for booting.

The software eventually supports the concept of relocatable proce-
dures with addresses bound at load time.

Aug 1949. Eckert and Mauchly, having formed their own company,
	complete the "BINAC" ("Binary Automatic Computer") for the
US Air Force.  Designed as a first step to in-flight computers, this
has dual (redundant) processors each with 700 tubes and 512 31-bit
words of memory.  Each processor occupies only 4 square feet of floor
space and can do 3500 additions or 1000 multiplications per second.

The designers are thinking mostly of their forthcoming "UNIVAC"
("Universal Automatic Computer") and don't spend much time making
the BINAC as reliable as it should be, but the tandem processors
compensate somewhat.

Sep 1949. Aiken's team completes the "Harvard Mark III".  This
	computer has separate magnetic drum memories for data and
instructions.  Only some of the data drums can be addressed by
the CPU; the others serve as secondary memory.  The total memory
capacity is 4000 instructions, 350 16-bit words in the main data
drums, and 4000 words more in the secondary memory.  The machine
contains over 5000 vacuum tubes and 2000 relays.

May 1950. A group at the National Physical Laboratory in England
	complete the "Pilot ACE" (pilot project for an "Automatic
Computing Engine"), which had been largely designed by Turing when
he was there in 1945-47.  The main memory of this computer is in
the form of 200 separate ultrasonic delay lines, thus allowing
better addressability than other ultrasonic-based machines.  An
additional group of short delay lines serve as registers, each of
which performs a particular operation automatically on a number
directed to it.  Most operations then consist simply of routing a
number, or a counted stream of numbers, from one delay line to
another.  Punch cards are used for input and output; a drum will
be added later for secondary memory.

1950.	Zuse's Z4 is finally completed and goes into service at
	ETH (Federal Polytechical Institute) in Zurich, Switzerland.
The design is modified so that it can do conditional jumps.  The
machine also implements a form of intstruction pipelining, with the
program tape being read 2 instructions ahead and various optimiz-
ations performed automatically.

The Z4 remains in use for 5 years at ETH and 5 more in France, and
Zuse soon begins making his machines commercially.  He eventually
sells some 300 machines before being bought out by Siemens.

Feb 1951.  Ferranti Ltd., of Manchester, England, completes the
	first commercial computer, yet another "Mark I" (but also
called the "Manchester Mark II", "MUDC", "MUEDC", or "MADAM").
It has 256 40-bit words of main memory and 16K words of drum,
and includes 8 index registers.  An eventual total of 8 of these
machines are sold.

(The index register's contents are added, not to the address taken
from an instruction, but to the entire instruction, thus potentially
changing the opcode!  Calling Mel...)

Mar 1951.  Presper Eckert and Mauchly, having sold their company to
	Remington Rand, complete the first "UNIVAC", which is the
first US commercial computer.  (The US census department is the first
customer.)  It has 1000 12-digit words of ultrasonic delay line memory
and can do 8333 additions or 555 multiplications per second; it con-
tains 5000 tubes and covers 200 square feet of floor.  For secondary
memory it uses magnetic tapes of nickel-coated bronze; these are 1/2
inch wide, and store 128 characters per inch.  

Fall 1951.  The Lyons company receives its reward for supporting the
	EDSAC, as T. R. Thompson and his team complete the "LEO I"
("Lyons Electronic Office I"), which is modeled closely after the
EDSAC.  Its ultrasonic memory is 4 times as large, and avoids the
usual temperature dependency by using one delay line as a master
and synchronizing the others to it instead of to a clock.

The Lyons company wants the LEO I for its own use -- payroll, inven-
tory, and so on; it is the first computer used for commercial calcul-
ations.  But other companies now turn out to be interested in the LEO,
and Lyons will soon find itself in the computer manufacturing business
as well.

1951.	Grace Murray Hopper (1906-1992), of Remington Rand, invents
	the modern concept of the compiler.

1952.	The EDVAC is finally completed.  It has 4000 tubes, 10,000
	crystal diodes, and 1024 44-bit words of ultrasonic memory.
Its clock speed is 1 MHz.

1952.	The IBM "Defense Calculator", later renamed the "701", the
	first IBM computer unless you count the SSEC, enters
production at Poughkeepsie, New York.  (The first one is delivered
in March 1953; 19 are sold altogether.  The machine is available
with 2048 or 4096 36-bit words of CRT memory; it does 2200 multi-
plications per second.)

1952.	Grace Murray Hopper implements the first compiler, the "A-0".
	(But as with "first computer", this is a somewhat arbitrary
designation.)

     ----------------------------------------------------

A few things have happened since then, too, but this margin is too
narrow...

Mark Brader, SoftQuad Inc., Toronto, utzoo!sq!msb, [email-masked]
	Nature is often much more interesting than we would like her to be.
	However when we finally do understand something, we strike our
	foreheads and cry "Of course!", and then marvel at how beautifully
	simple it was all the time.			-- Leigh Palmer

From: [email-masked] (Charles Lasner)
Newsgroups: alt.folklore.computers
Subject: Re: A Chronology of Digital Computing to 1952 (improved version)

In article <[email-masked]> [email-masked] (Mark Brader) writes:
>
>1931-2. E. Wynn-Williams, at Cambridge, England, uses thyratron
>	vacuum tubes to construct a binary digital counter for use
>in connection with physics experiments.

A bone to pick: Thyratrons aren't vacuum tubes.  They deliberately contain
a gas that causes them to exhibit behavior unlike vacuum tubes: they latch on
once driven to conduct.  More modern Silicon Controlled Rectifiers (SCR's) work
pretty much the same way.  I assume this very characteristic is the
distinguishing feature here.  (I believe that thyratrons were developed by
noticing the effects within defective vacuum tubes which contained unwanted
gases.  Newer techniques were invented (getters) to eliminate the gas in
vacuum tubes, but the opposite is true of voltage regulator tubes, cold-cathode
gas-filled rectifiers, mercury-vapor filled rectifiers, and thyratrons.)

cj "totally tubular" l

From: [email-masked] (Lon Stowell)
Newsgroups: alt.folklore.computers
Subject: Re: A Chronology of Digital Computing to 1952 (improved version)

>In article <[email-masked]> [email-masked] (Mark Brader) writes:
>>
>>1931-2. E. Wynn-Williams, at Cambridge, England, uses thyratron
>>	vacuum tubes to construct a binary digital counter for use
>>in connection with physics experiments.

In article <[email-masked]> [email-masked] (Charles Lasner) writes:
>
>A bone to pick: Thyratrons aren't vacuum tubes.  They deliberately contain
>a gas that causes them to exhibit behavior unlike vacuum tubes: they latch on
>once driven to conduct.  More modern Silicon Controlled Rectifiers (SCR's) work
>pretty much the same way. 

   Odd, thyratrons were usually used for servo motor controls...never
   heard of them being used in a computer before.

   The original poster couldn't be confusing the thyratron with the
   2D21 type coincidence tubes...often used for early digital
   computation devices.   ?????

From: [email-masked] (Hans-Georg Zipperer)
Newsgroups: alt.folklore.computers
Subject: Re: A Chronology of Digital Computing to 1952 (improved version)

In article <[email-masked]> [email-masked] (Lon Stowell) writes:
[...]
>   Odd, thyratrons were usually used for servo motor controls...never
>   heard of them being used in a computer before.

The first electronic desktop calculator, 'Anita', contained some hundred
thyratrons, 1 decatron, a few vacuum tubes, 1 transistor and some hundred
selenium diodes.  Thyratrons are smaller and simpler as vacuum tubes because
they don't need a heater, so it was possible to build an electronic calculator
that was not bigger as the usual electro-mechanical machines.  They have a
further advantage: the ionized gas emits orange light when the thyratron is
conducting.  This makes a working 'Anita' a pretty spectacular sight.

A decatron is an integrated decimal counter: 10 thyratron systems (1 cathode
and 10 anodes) in a single tube.  Exactly one of them is in the conducting
state.  By applying a pulse, the discharge switches to the next anode.
-- 
  Hans-Georg Zipperer     Universit"at Stuttgart, Institut f"ur Informatik
  Tel. (0711) 7816-405    e-mail: [email-masked]

From: [email-masked] (PDP11 Hacker .....)
Newsgroups: alt.folklore.computers
Subject: Re: A Chronology of Digital Computing to 1952 (improved version)

In article <[email-masked]>, [email-masked] (Michael Covington) writes...
>In article <[email-masked]> [email-masked] (Lon Stowell) writes:
>>In article <[email-masked]> [email-masked] (Charles Lasner) writes:
>>>
>>>A bone to pick: Thyratrons aren't vacuum tubes.  They deliberately contain
>>>a gas that causes them to exhibit behavior unlike vacuum tubes: they latch on
>>>once driven to conduct.  More modern Silicon Controlled Rectifiers (SCR's) work
>>>pretty much the same way. 
>....>
>>   The original poster couldn't be confusing the thyratron with the
>>   2D21 type coincidence tubes...often used for early digital
>>   computation devices.   ?????
> 
>I thought the 2D21 *was* a thyratron (i.e., a gas tetrode).  Isn't it?
> 

According to my valve data book, the 2D21 is an equivalent to the EN91 which is
a Xenon tetrode thyratron. 

> 
>-- 
>:-  Michael A. Covington, Associate Research Scientist        :    *****
>:-  Artificial Intelligence Programs      [email-masked] :  *********
>:-  The University of Georgia              phone 706 542-0358 :   *  *  *
>:-  Athens, Georgia 30602-7415 U.S.A.     amateur radio N4TMI :  ** *** **  <><

-tony

From: [email-masked] (PDP11 Hacker .....)
Newsgroups: alt.folklore.computers
Subject: Re: A Chronology of Digital Computing to 1952 (improved version)

In article <[email-masked]>, [email-masked] (Hans-Georg Zipperer) writes...
>In article <[email-masked]> [email-masked] (Lon Stowell) writes:
>[...]
>>   Odd, thyratrons were usually used for servo motor controls...never
>>   heard of them being used in a computer before.
> 
>The first electronic desktop calculator, 'Anita', contained some hundred
>thyratrons, 1 decatron, a few vacuum tubes, 1 transistor and some hundred
>selenium diodes.  Thyratrons are smaller and simpler as vacuum tubes because
>they don't need a heater, so it was possible to build an electronic calculator

I'm sure that some thyratrons were hot-cathode. In fact, the cold-cathode ones
used in computing/digital counters were more often called 'trigger tubes' in
the UK. 

>that was not bigger as the usual electro-mechanical machines.  They have a
>further advantage: the ionized gas emits orange light when the thyratron is
>conducting.  This makes a working 'Anita' a pretty spectacular sight.

Depends on the gas. Some thyratrons were blue or purple.

> 
>A decatron is an integrated decimal counter: 10 thyratron systems (1 cathode
>and 10 anodes) in a single tube.  Exactly one of them is in the conducting
>state.  By applying a pulse, the discharge switches to the next anode.

Seems like a reasonable explanation of the dekatron. They are cold cathode. 

>-- 
>  Hans-Georg Zipperer     Universit"at Stuttgart, Institut f"ur Informatik
>  Tel. (0711) 7816-405    e-mail: [email-masked]

-tony

From: [email-masked] (Peter D. Smith)
Newsgroups: alt.folklore.computers
Subject: Re: removing a certain file on unnix system
Date: 6 Sep 1994 22:34:20 GMT

ObFolklore:  Earliest Computer Construction Article

I recently read what I think is the very first build-this-computer-at-home
construction article.  No, it's not the ELF, and it's not the Altair --
they're off by (drum roll please) fifteen years.

The series was in the Nov 1950 to Nov 1951 copies of 'Radio Electronics', 
and described 'Simon', a relay computer. The whole thing is (oddly) the size
of an Altair; numbers are two bits (but there's a description of 'double
precision' four-bit numbers).

The architecture is, to put it mildly, bizarre.  For example, the adder
circuitry is constantly adding numbers -- it's got two special input
registers and an output register.  Need to add numbers?  Drop them into
the input registers, and then grab the result from the output register.
Don't need to add two numbers?  The adder will add what's in the input
registers anyway, and drop the result into the output register.

There's also a description in the (Nov?) 1950 (?) Scientific American,
as well as a description in the book 'Giant Brains'