A Chronology of Digital Computing Machines (to 1952)

I thought this material would be of interest to this group, considering
the recent discussions of early computers and this can be an example of a one page research paper.

I have compiled it from two
sources. The primary one that I used is:

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

I recommend that book, by the way, but with some reservations. The author
is a journalist rather than a computer person. From time to time this shows,
but it's generally clear what he means even if he doesn't actually say that.
In any case, he does tell the story in an interesting and readable fashion.

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

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

The criteria for including a machine in this chronology were that it either
was technologically innovative or was well known and influential; certain
particularly innovative inventions have also been included as of the first
time that they were described. When I refer to a machine as being able to do
some operation, I mean that it can do it more or less without assistance from
the user. This disqualifies the abacus from consideration, for instance;
similarly, a user wanting to subtract 16 on a 6-digit Pascaline could do it
by adding 99984, but this does not count as ability to do subtraction.

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 is a small
prototype, but would fill a small room if it has memory or significant
programmability (of course, the two tend to go together).

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


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 perhaps includes an overflow
indicator bell. Mounted on the machine is a set of Napier's Rods, a
memory aid facilitating multiplications. The machine and plans are lost
and forgotten in the war that is going on. (The plans were rediscovered
in 1935, lost again in the war, and re-rediscovered by the same man in 1956!
The machine was reconstructed in 1960 and found to be workable.)
Schickard was a friend of the astronomer Kepler.

1644-5. Blaise Pascal (1623-1662), of Paris, makes his "Pascaline". This
5-digit machine can only add, and that probably not as reliably as
Schickard's, but at least it doesn't get forgotten -- it establishes the
computing machine concept in the intellectual community. (Pascal sold about
10-15 of the machines, some supporting as many as 8 digits, and a number of
pirated copies were also sold. No patents...)
This is the same Pascal who invented the bus.

1674. Gottfriend Wilhelm von Leibniz (1646-1716), of Leipzig, makes his
"Stepped Reckoner". This 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.
But its carry mechanism requires user intervention and doesn't really work
in all cases anyway. The calculator is powered by a crank.
This is the same Leibniz or Leibnitz who co-invented 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 calcu-
lator 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 int-
ervals. 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.

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

1832. Babbage produces 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 was to have
operated on 20-digit numbers and 6th-order difference, but no more than
this prototype piece was ever assembled.

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

1836. Babbage produces the first design for his "Analytical Engine".
Whether this machine, if built, would have been a computer or not
depends on how you define "computer". It lacked the "stored-program"
concept necessary for implementing a compiler; the program was in read-only
memory, specifically in the form of punch cards. In this article such a
machine will be called a "program-controlled calculator".
The final design had three punch card readers for programs and data.
The memory had 50 40-digit words of memory and 2 accumulators. Its program-
mability included the conditional-jump concept. It also included a form of
microcoding: the meaning of instructions depended on the positioning of
metal studs in a slotted barrel. It would have done an addition in
3 seconds and a multiplication or division in 2-4 minutes.

1842. Babbage's difference engine project is officially cancelled.
(Babbage was spending too much time on 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.

1853. To Babbage's delight, Scheutz and Scheutz complete the first really
useful difference engine, operating on 15-digit numbers and 4th-order
differences, with a printer.

1858. The difference engine of 1853 does its only useful calculation,
producing a set of astronomical tables for an observatory in Albany,
New York. The person who spent money on it is fired and the machine ends up
in the Smithsonian Institute. (The Scheutzes did make a second similar machine,
which had a long useful life in the British government.)

1871. Babbage produces a prototype section of the Analytical Engine's
"mill" (CPU) and printer. No more is ever assembled.

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 becomes somewhat forgotten and is unknown to most of the people
mentioned in the last part of this chronology.

1885. Dorr E. Felt (1862-1930), of Chicago, makes his "Comptometer".
This is the first calculator where numbers are entered by pressing
keys as opposed to being dialed in or similar awkward methods.

1889. Felt invents the first printing desk calculator.

1890. US Census results are tabulated for the first time with significant
mechanical aid: the punch card tabulators of Herman Hollerith
(1860-1929) of MIT, Cambridge, Mass. This is the start of the punch card
industry (thus establishing the size of the card, the same as a US $1 bill
(then)). The cost of the census tabulation rises by 98% from the previous
one, in part because of the temptation to use the machines to the fullest
and tabulate more data than formerly possible. The use of electricity to
read the cards is also significant.

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. (The calculators are still hand
powered at this point, but electrified ones follow in not too many years.)

1937. George Stibitz (c.1910-) of 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", which solves a mathematical problem
by considering as a mathematical device the theoretical simplified computer
that came to be called 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 completes a prototype mechanical
programmable calculator, later called the "Z1". Its memory used sliding
metal parts and stored about 1000 bits. The arithmetic unit was unreliable.

Oct 1939. Stibitz and Samuel Williams complete the "Model I", a calculator
using relay logic. It is controlled through modified teletypes
and these can be connected through phone lines. Later machines in the series
also have some programmability.

c.Oct 1939. John V. Atanasoff (1903-) and Clifford Berry, of Iowa State
College, Ames, Iowa, complete a prototype 16-bit adder. This
is the first machine to calculate using vacuum tubes.

c.1940. Zuse completes the "Z2", keeping the mechanical memory but using
relay logic. He can't interest anyone in funding him.

Dec 1941. Zuse, having promised to a research institute a special-purpose
calculator for their needs, actually builds them the "Z3", which
is the first operational program-controlled calculator, and has 64 22-bit
words of memory. However, its programmability doesn't include a conditional-
jump instruction; Zuse never had that idea. The program is on punched tape.
The machine includes 2600 relays, and a multiplication takes 3-5 seconds.

Spring 1942. Atanasoff and Berry complete a special-purpose calculator 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) mounted on two revolving
drums. The clock speed is 60 Hz, and an addition takes 1 second.
For secondary memory it uses punch cards, with the holes being burned
rather than punched in them, moved around by the user. (The punch card
system's error rate was never reduced beyond 0.001%, which wasn't good enough.)
Atanasoff then left Iowa State, and apparently lost all interest
in digital computing machines.
[You can read more about the ABC in an article in one of the issues
of Scientific American, which called it the first computer.]

Jan 1943. Howard H. Aiken (1900-1973) and his team at Harvard University,
Cambridge, Mass. (with backing from IBM), complete the "ASCC
Mark I" ("Automatic Sequence-Controlled Calculator Mark I"). This is the first
program-controlled calculator to be widely known: Aiken was to Zuse as Pascal
to Schickard. The machine is about 60 feet long and weighs 5 tons; it has
72 accumulators.

Dec 1943. Alan Turing and his team at Bletchley Park, near Cambridge, England,
complete the first version of the "Colossus". This is a secret,
special-purpose decryption machine, not exactly a calculator but close kin.
It includes 2400 tubes for logic and reads characters (optically) from 5
long paper tape loops moving at 5000 characters per second.

Nov 1945. John W. Mauchly (pronounced Mawkly; 1907-80) and J. Presper Eckert
(1919-) and their team at the Moore School of the University of
Pennsylvania, Philadelphia, complete the "ENIAC" ("Electronic Numerator,
Integrator, Analyzer, and Computer") for the US Army's Ballistics Research
Lab. (Too late for the war and 200% over budget -- problems that would face
Eckert and Mauchly again on later projects.)
The machine is a secret (until Feb 1946) program-controlled calculator.
Its only memory is 20 10-digit accumulators (4 were originally planned).
The accumulators and logic use vacuum tubes, 17648 of them altogether.
The machine weighs 30 tons, covers about 1000 square feet of floor, and
consumes what is either 174 kilowatts (233 horsepower) or 174 hp (130 kW).
Its clock speed is 100 kHz; it can do 5000 additions per second, 333 multip-
lications per second. It reads data from punch cards, and the program is
set up on a plugboard (considered reasonable since the same or similar
program would tend to be used for weeks at a time).
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.

1945-46. John von Neumann (1903-1957) joins the ENIAC team and writes a
report describing the future computer eventually built as the
"EDVAC" ("Electronic Discrete Variable Automatic Computer" (!)). This
report was the first description of the design of a stored-program computer.
An early draft which fails to credit other team members such as Eckert
and Mauchly gets too-wide distribution, leading to von Neumann getting
too much credit, e.g., the term "von Neumann computer" which is derived from
this paper.

Jan 1948. Wallace Eckert (1902-1971, no relation to Presper Eckert and not
mentioned again in this article) of IBM, with his team, completes
the "SSEC" ("Selective Sequence Electronic Calculator"). This technological
hybrid has vacuum tube logic with 8 20-digit registers, 150 20-digit words
of relay memory, and a program that is partly stored but also controlled
by a plugboard. IBM considers it the first computer.

Jun 1948. Max Newman, F. C. Williams, and their team at Manchester Univers-
ity, Manchester, England, complete a prototype machine called the
"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 invented by Williams, 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 bit
unreliable but is fast, relatively cheap, and much more compact (with room
for about 1024 or 2048 bits per tube) than any other memory then existing.
The Mark I uses six of them, but I don't know of how many bits.
Its 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 in different places.
Newman was the first person shown Turing's 1937 paper in draft form.

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 it advanced to full-time operational status gradually. Originally
it had 3300 tubes and 8900 crystal diodes. It occupied 2500 square feet
of floor. Its 2048 16-bit words of CRT memory used up tubes so fast they
were costing $32000 per month.
This was the first computer designed for real-time work, hence the
short word size; it could do 500000 additions or 50000 multiplications
per second.

Spring 1949. Forrester conceives the idea of magnetic core memory. The first
practical form, 4 years later, will replace the Whirlwind's
CRT memory and render all then existing types obsolete.

Jun 1949. Maurice Wilkes (1913-) and his team at Cambridge University
complete the "EDSAC" ("Electronic Delay Storage Automatic Computer"),
which is closely based on the EDVAC design report from von Neumann's group.
This is the first operational stored-program computer that's not a prototype.
Its I/O is by paper tape, and it has a sort of mechanical read-only memory
for booting, consisting of rotary telephone switches.
Its main memory is of another new type, invented by Eckert: the
"ultrasonic" or "delay line" memory. In this type, the data is repeatedly
converted back and forth between electrical pulses and ultrasonic pulses;
only the bits currently in electrical form are accessible. (The ultrasonic
pulses were typically fired from one end of a tank of mercury to the other,
though other substances were also used.) In the EDSAC, 32 mercury tanks
5 feet long give a total of 256 35-bit words of memory.

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.

Feb 1951. Ferranti Ltd., of Manchester, England, completes the first
commercial computer, also called the "Mark I". 8 of them are sold.

Mar 1951. Eckert and Mauchly, having sold their company to Remington Rand,
complete the first UNIVAC, which is the first US commercial computer.
It has 1000 12-digit words of ultrasonic memory and can do 8333 additions
or 555 multiplications per second; it contains 5000 tubes and covers
200 square feet of floor.

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

1951-52. The EDVAC is finally completed. It has 4000 tubes, 10000 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 memory is electrostatic and has 4096 36-bit words;
it does 2200 multiplications per second.)

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


A few things have happened since then, too, but that is another paper..

"Inventions reached their limit long ago,
and I see no hope for further development."
-- Julius Frontinus, 1st century A.D.


Computer History Links

This is a selection of the best computing history links I've found. This page doesn't try to be comprehensive, but the hope is that every major computing history site is no more than two links away (i.e. linked to on this page or on one of the pages I link.) Also note that I'm concentrating on the computers here, rather than on the people who made them possible. Maybe a "people" page will follow.


The picture at right is of a Cray Y-MP. It wasn't too long ago (1990 or so) that this was the fastest computer money could buy now it's just another has-been. (Picture swiped from Cray Research, Inc. promotional materials.)


"Welcome to the future, for it shall soon be the past. Respect the past, for it was once all that was humanly possible." -- Unknown


The Virtual Museum of Computing is a great set of links to other lodes of computer history.

Looking for information on an older CPU? What if you want to find out what the real differences between CISC and RISC are? How about info on Intel's dodo the i432? The site to solve your woes is the CPU Info Center.

Jones's Punched Card Page has all sorts of interesting information about that thankfully bygone input medium, the punched card. It includes encoding schemes and historical info.

For a lighter look at computer history, visit The Retrocomputing Museum. This page showcases some of the "freaks, jokes, and fossils of computing history."

I use The SPEC List to build up a quick-and-dirty profile of an older machine's speed, especially as compared to newer machines. The list includes benchmarks for many older machines and many newer ones, so it's easy to get a general idea of the relative speeds of two machines. (Yes, I know this is hardly a perfect method, but it suits my purposes.)

Naturally, you can't miss Yahoo's Computer History Links.


The Obsolete Computer Museum is perhaps the finest museum of micros on the net. They haven't got everything, but they're working on it!

The Apple ][ Home Page is the perfect place for all those old Apple ][ fans who never forgot how fun those old machines were. Best of all, there's now a few really good free Apple ][ emulators for various platforms available.

The Apple Lisa Page offers a peek at the coolest micro you've never used.

Yes, it's true, The BBC Lives! Apparently, the BBC Micro is to England what the Apple ][ is to America.

Bob's Computer Museum is definitely worth a visit. This page is based on Bob's computer collection, which mainly features old micros and minis up through not-so-old PCs and workstations. It's in this section, because the focus of the collection is the micros rather than the minis.

Minicomputers and Workstations

The PDP-11 UNIX Preservation Society is dedicated to preserving elements of the PDP-11 UNIX culture that molded so much of today's hacker culture. Of particular interest is the PDP-11 simulator and the UNIX version 5, 6 and 7 system binaries! Other emulators and OSes are also available.

Doug Jones's PDP-8 Index a comprehensive-looking set of links and information about one of the most popular minis ever.

This Old SGI is an encyclopedic site of tips and techniques for keeping an old Silicon Graphics 4D-class box running.

Ákos Varga has a well-designed site up dedicated to the PDP-11. Especially interesting is that Varga, a Hungarian, writes knowledgeably about the clone work being done behind the now-fallen Iron Curtain. Varga also has a collection of other Digital equipment -- minis, micros and terminals, mainly -- beautifully showcased in the DECadence section of his site.

Mainframes and Other Large Machines

The ENIAC 50th Anniversary Page has lots of links to programs that the University of Pennsylvania put on in 1996. Of particular interest are the ENIAC-on-a-Chip project and the ENIAC Simulator (neither project is fully completed).

While you're waiting for the ENIAC simulator, try EdsacPC, a faithful emulation of the EDSAC for Windows 95/NT machines. (An older Macintosh version is also available, but it reportedly doesn't work on many PowerMacs.)

The Survey of High Performance Computing Systems has all sorts of interesting information on the computer industry's version of monster trucks.

Fee Computer Services has a nice site dedicated mainly to IBM mainframes of the 1960's and 1970's.



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