History of computing





Overview

This narrative presents the major developments in the history of computing
and tries to put them into perspective. For a detailed timeline of events,
see computing timeline.

Earliest Devices

Humanity has used devices to aid in computation for millennia; an example is
the abacus—a Chinese invention. The first machines that could arrive
at the answer to an arithmetical question more or less autonomously started
to appear in the 1600s, limited to addition and subtraction at first, but
later also able to perform multiplications. These devices used techniques
such as cogs and gears first developed for clocks. The difference engines of
the 1800s could carry out a long sequence of such calculations in order to
construct mathematical tables, but were not widely used.

The defining feature of a "universal computer" is programmability, which
allows the computer to emulate any other calculating machine by changing a
stored sequence of instructions. In 1801, Joseph-Marie Jacquard developed a
loom in which the pattern being woven was controlled by punched cards. The
series of cards could be changed without changing the mechanical design of
the loom. This was a landmark point in programmability.

In 1835 Charles Babbage described his analytical engine. It was the plan of
a general-purpose programmable computer, employing punch cards for input and
a steam engine for power. While the plans were probably correct, disputes
with the artisan who built parts, and the end of government funding, made it
impossible to build. Ada Lovelace, Lord Byron's daughter, translated and
added notes to the "Sketch of the Analytical Engine" by L. F. Menabrea. She
has become closely associated with Babbage. Some claim she is the world's
first computer programmer, however this claim and the value of her other
contributions are disputed by many. The Difference Engine II has been built
and is operational at the London Science Museum; it works as Babbage
designed it and has disproven the theory that Babbage was incapable of
manufacturing parts of the required precision.

In 1890 the United States Census Bureau used punch cards and sorting
machines designed by Herman Hollerith to handle the flood of data from the
decennial census mandated by the Constitution. Hollerith's company
eventually became the core of IBM.

In the twentieth century, electricity was first used for calculating and
sorting machines. Earlier mechanical calculators, cash registers, accounting
machines, and so on were redesigned to use electric motors. Before World War
II, mechanical and electrical analog computers were the 'state of the art',
and many thought they were the future of computing. Analog computers use
continuously varying amounts of physical quantities, such as voltages or
currents, or the rotational speed of shafts, to represent the quantities
being processed. An ingenious example of such a machine was the Water
integrator built in 1936. Unlike modern digital computers, analog computers
are not very flexible, and need to be reconfigured (i.e., reprogrammed)
manually to switch them from working on one problem to another. Analog
computers had an advantage over early digital computers in that they could
be used to solve complex problems while the earliest attempts at digital
computers were quite limited. But as digital computers have become faster
and used larger memory (e.g., RAM or internal store), they have almost
entirely displaced analog computers.

First Generation of Computers

The era of modern computing began with a flurry of development before and
during World War II, as electronic circuits, vacuum tubes, capacitors, and
relays replaced mechanical equivalents and digital calculations replaced
analog calculations. The computers designed and constructed then have been
called 'first generation' computers. First generation computers were usually
built by hand using circuits containing relays or vacuum valves (tubes), and
often used punched cards or punched paper tape for input and as the main
(non-volatile) storage medium. Temporary, or working storage, was provided
by acoustic delay lines (which use the propagation time of sound in a medium
such as wire to store data) or by Williams tubes (which use the ability of a
television picture tube to store and retrieve data). By 1954, magnetic core
memory was rapidly displacing most other forms of temporary storage, and
dominated the field through the mid-1970s. A example of a practical WWII era
machine was the Target Data Computer employed in American submarines, that
allowed the operator to input a few pieces of data, such as the sub's speed
and heading, and some observed variables about a target vessel. The TDC
would then calculate and display the exact aiming point for firing
torpedoes. The TDC was a part of what led to total American dominance in
submarine warfare in the Pacific.

This era saw numerous electromechanical calculating devices of various
capabilities which had a limited impact on later designs. In 1938 Konrad
Zuse started construction of the first Z-series, electromechanical
calculators featuring memory and limited programmability. Zuse was
(inadequately) supported by the German Wehrmacht which used his
proto-computers for the production of guided missiles. The Z-series
pioneered many advances, such as the use of binary arithmetic and floating
point numbers. In 1940, the Complex Number Calculator, a calculator for
complex arithmetic based on relays, was completed. It was the first machine
ever used remotely over a phone line. In 1938 John Vincent Atanasoff and
Clifford E. Berry of Iowa State University developed the Atanasoff Berry
Computer (ABC), a special purpose computer for solving systems of linear
equations, and which employed capacitors fixed in a mechanically rotating
drum, for memory.

During World War II, the British made significant efforts at Bletchley Park
to break German military communications. The main German cypher system (the
Enigma in several variants) was attacked with the help of purpose built
'Bombes' which helped find possible Enigma keys after other techniques had
narrowed down the possibilities. The Germans also developed a series of
cypher systems (called Fish cyphers by the British) which were quite
different than the Enigma. As part of an attack against these cyphers,
Professor Max Newman and his colleagues (including Alan Turing) designed
Colossus.

Colossus was the first programmable (to some extent) electronic computer.
Since solid state electronics had yet to be invented, it used vacuum tubes,
had a paper-tape input and allowed some programmability. It was built and
used to decrypt German wartime cyphers. Ten second-generation Colossus
machines were built (there were at least two variants), but details of their
existence, design, and use were kept secret well into the 1970s. Winston
Churchill is said to have personally issued an order for their destruction
into pieces no larger than a man's hand. Due to this secrecy Colossus was
not included in many histories of computing. There is an active project to
build a copy of one of the Colossus machines.

Turing's pre-War work was a major influence on the design of the modern
computer, and after the War he went on to design, build and program some of
the earliest computers at the National Physical Laboratory and at the
University of Manchester. His 1936 paper in Mind included a description of
what is now called the Turing machine, a purely theoretical device invented
to formalize the notion of algorithm execution. Modern computers are
Turing-complete (i.e., equivalent algorithm execution capability to a
universal Turing machine), except for their finite memory. Turing
completeness is a threshold capability separating general-purpose computers
from their special-purpose predecessors. It is as good a criterion as any
for defining "the first computer", but unfortunately even with this
restriction there is no simple answer as to which computer was the first.
Babbage's Analytical Engine was the first design of a Turing-complete
machine, Zuse's Z3 was the first Turing-complete working machine (but this
was unknown to Zuse and was proved only in 1998 after his death), and the
electronic ENIAC was the first working Turing-complete computer designed and
used as such. The ABC machine was not programmable, though a complete
computer in the modern sense in most other respects. George Steibitz and
colleagues at Bell Labs in NY City produced several relay based 'computers'
in the late '30s and early '40s, but were concerned mostly with problems of
telephone system control, not computing. Their efforts were a clear
antecedent for another electromechanical American machine, however.

The Harvard Mark I (officially, the Automatic Sequence Controlled
Calculator) was a general purpose electro-mechanical computer built with IBM
financing and with assistance from some IBM personnel under the direction of
Harvard mathematician Howard Aiken. Its design was influenced by the
Analytical Engine. It used storage wheels and rotary switches in addition to
electromagnetic relays, was programmable by punched paper tape, and
contained several calculators working in parallel. Later models contained
several paper tape readers and the machine could switch between readers
based on a condition. Nevertheless, this does not quite make the machine
Turing-complete. Development began in 1939 at IBM's Endicott laboratories;
the Mark I was moved to Harvard University to begin operation in May 1944.

The US-built ENIAC (Electronic Numerical Integrator and Computer), the first
large-scale general-purpose electronic computer, publicly validated the use
of electronics for large-scale computing. This was crucial for the
development of modern computing, initially because of the enormous speed
advantage, but ultimately because of the potential for miniaturization.
Built under the direction of John Mauchly and J. Presper Eckert, it was
1,000 times faster than its contemporaries.

Its development and construction lasted from 1941 to full operation at the
end of 1945. When its design was proposed, many researchers believed that
the thousands of delicate valves (ie, vacuum tubes) would burn out often
enough that the ENIAC would be so frequently down for repairs as to be
useless. It was, however, capable of 5,000 simple calculations a second for
hours at a time between valve failures. It was programmable, not only by
rewiring as originally designed, but later also with fixed wiring executing
stored programs set in function table memory using a scheme named after John
von Neumann.

By the time the ENIAC was successfully operational, the plans for the EDVAC
were already in place. Insights from experience with ENIAC led to the EDVAC
design, which had unrivalled influence in the initial stage of the computer
revolution. The design team was led by von Neumann.

The essentials of the EDVAC design have come to be known as the von Neumann
architecture: programs are stored in the same memory 'space' as the data.
Unlike the ENIAC, which used parallel processing, it used a single
processing unit. This design was simpler and was the first to be implemented
in each succeeding wave of miniaturization, and increased reliability. The
EDVAC design can be seen as the "Eve" from which nearly all current
computers derive their architecture.

The first working von Neumann machine was the Manchester "Baby", built at
the University of Manchester in 1948; it was followed in 1949 by the
Manchester Mark I computer which functioned as a complete system using the
Williams tube for memory. This University machine became the prototype for
the Ferranti Mark I, the world's first commercially available computer
(although some point out that LEO I was the computer that was used for the
world's first regular routine office computer job in November 1951). The
first model was delivered to the University in February, 1951 and at least
nine others were sold between 1951 and 1957.

Later in 1951, the UNIVAC I (Universal Automatic Computer), delivered to the
U.S. Census Bureau, was the first commercial computer to attract U.S. public
attention. Although manufactured by Remington Rand, the machine often was
mistakenly referred to as the "IBM UNIVAC". Remington Rand eventually sold
46 machines at more than $1 million each. UNIVAC was the first 'mass
produced' computer; all predecessors had been 'one-off' units. It used 5,200
vacuum tubes and consumed 125 kW of power. It used a mercury delay line
capable of storing 1,000 72-bit words for memory. Unlike earlier machines it
did not use a punch card system but a metal tape input.

Second Generation

The next major step in the history of computing was the invention of the
transistor in 1947. This replaced the fragile and power hungry valves with a
much smaller and more reliable component. Transistorised computers are
normally referred to as 'Second Generation' and dominated the late 1950s and
early 1960s. Despite using transistors and printed circuits these computers
were still large and primarily used by universities, governments, and large
corporations. For example the IBM 650 of 1954 weighed over 900 kg, the
attached power supply weighed around 1350 kg and both were held in separate
cabinets of roughly 1.5 meters by 0.9 meters by 1.8 meters. It cost $500,000
or could be leased for $3,500 a month.

In 1955, Maurice Wilkes invented microprogramming, now almost universally
used in the implementation of CPU designs. The CPU instruction set is
defined by a type of programming.

In 1956, IBM sold its first magnetic disk system, RAMAC (Random Access
Method of Accounting and Control). It used 50 24-inch metal disks, with 100
tracks per side. It could store 5 megabytes of data and cost $10,000 per
megabyte.

The first high-level general purpose programming language, FORTRAN, was also
being developed at IBM around this time.

In 1959 IBM shipped the transistor-based IBM 1401 mainframe, which used
punch cards. It proved a popular general purpose computer and 12,000 were
shipped, making it the most successful machine in computer history. It used
a magnetic core memory of 4000 characters (later expanded to 16,000 bytes).
Many aspects of its design were based on the desire to replace punched card
machines which were in wide use from the 1920s through the early 70s.

In 1960 IBM shipped the transistor-based IBM 1620 mainframe, which also used
punch cards. It proved a popular scientific computer and about 2,000 were
shipped. It used a magnetic core memory of up to 60,000 decimal digits.

In 1964 IBM announced the S/360 series, which was the first family of
computers that could run the same software at different combinations of
speed, capacity and price. It also pioneered the commercial use of
microprograms, and an extended instruction set designed for processing many
types of data, not just arithmetic. In addition, it unified IBM's product
line, which prior to that time had included both a "commercial" product line
and a separate "scientific" line. The software provided with System/360 also
included major advances, including commercially available multi-programming,
new programming languages, and independence of programs from input/output
devices. Over 14,000 System/360 systems were shipped by 1968.

Also in 1964, DEC launched the PDP-8 much smaller machine intended for use
by technical staff in laboratories and for research.

Third Generation and Beyond

The explosion in the use of computers began with 'Third Generation'
computers. These relied on Jack St. Claire Kilby's invention of the
integrated circuit (or microchip), which later led to Robert Noyce's
invention of the microprocessor.