Introduction to the History of Computing
Lecture 34, CSE1301 Computer Programming, 2003
Notes and references
Sundials, Stonehenge
Abacus
http://www.ee.ryerson.ca:8080/~elf/abacus/history.html
Astrolabe
http://www.hps.cam.ac.uk/starry/isaslabe.html
Da Vinci’s Mechanical Calculator
http://www.maxmon.com/1500ad.htm
Da Vinci was a genius: painter, musician, sculptor, architect, engineer, and
so on. However, his contributions to mechanical calculation remained hidden
until the rediscovery of two of his notebooks in 1967.
These notebooks, which date from sometime around the 1500s, contained
drawings of a mechanical calculator, and working models of da Vinci's device
have since been constructed.
Napier’s Bones
http://www.maxmon.com/1600ad.htm
In the early 1600s, a Scottish mathematician called John Napier invented a
tool called Napier's Bones, which were multiplication tables inscribed on strips
of wood or bone.
Napier, who was the Laird of Merchiston, also invented logarithms, which greatly
assisted in arithmetic calculations.
Slide Rules
http://www.hpmuseum.org/sliderul.htm
http://www.oughtred.org/
http://www.maxmon.com/1600ad.htm
In 1621, an English mathematician and clergyman called William Oughtred
used Napier's logarithms as the basis for the slide rule (Oughtred invented
both the standard rectilinear slide rule and the less commonly used circular
slide rule). However, although the slide rule was an exceptionally effective tool
that remained in common use for over three hundred years, like the abacus it
also does not qualify as a mechanical calculator
In 1614, John Napier discovered the logarithm which made it possible to perform
multiplications and divisions by addition and subtraction. (ie: a*b =
10^(log(a)+log(b)) and a/b = 10^(log(a)-log(b)).)
This was a great time saver but there was still quite a lot of work required. The
mathematician had to look up two logs, add them together and then look for the
number whose log was the sum. Edmund Gunter soon reduced the effort by drawing a
number line in which the positions of numbers were proportional to their logs.
The scale started at one because the log of one is zero. Two numbers could be
multiplied by measuring the distance from the beginning of the scale to one factor
with a pair of dividers, then moving them to start at the other factor and reading the
number at the combined distance.
Picture of a 2 foot Gunter scale (~110K) The yellow spots are brass inserts to
provide wear resistance at commonly used points.
Closeup on the Gunter scale (~72K)
Soon afterwards, William Oughtred simplified things further by taking two Gunter's
lines and sliding them relative to each other thus eliminating the dividers.
In the years that followed, other people refined Oughtred's design into a sliding bar
held in place between two other bars. Circular slide rules and cylindrical/spiral slide
rules also appeared quickly. The cursor appeared on the earliest circular models but
appeared much later on straight versions. By the late 17th century, the slide rule was a
common instrument with many variations. It remained the tool of choice for many for
the next three hundred years.
Pascal’s Arithmetic Engine
http://www.maxmon.com/1640ad.htm
In 1640, Pascal started developing a
device to help his father add sums of
money. The first operating model, the
Arithmetic Machine, was introduced in
1642, and Pascal created fifty more
devices over the next ten years. (In
1658, Pascal created a scandal when,
under the pseudonym of Amos
Dettonville, he challenged other
mathematicians to a contest and then
awarded the prize to himself!)
a
However, Pascal's device could only add and subtract, while multiplication
and division operations were implemented by performing a series of
additions or subtractions. In fact the Arithmetic Machine could really only
add, because subtractions were performed using complement techniques, in
which the number to be subtracted is first converted into its complement,
which is then added to the first number. Interestingly enough, modern
computers employ similar complement techniques.
Leibnez’s step reckoner
http://www.maxmon.com/1670ad.htm
Leibniz developed Pascal's ideas and, in 1671, introduced the Step
Reckoner, a device which, as well as performing additions and subtractions,
could multiply, divide, and evaluate square roots by series of stepped
additions.
Leibniz also strongly advocated the use of the binary number system, which
is fundamental to the operation of modern computers.
Jacquard’s punched card
http://history.acusd.edu/gen/recording/jacquard1.html
exhibit caption: "Joseph Marie Jacquard's inspiration of 1804 revolutionized patterned
textile waving. For the first time, fabrics with big, fancy designs could be woven
automatically by one man working without assistants. Jacquard never obtained a
patent for this device. His 1801 patent, issued for an improved drawloom, is often
mistaken for the punched-card controlled device that bears his name. Working in
Lyon, France, Jacquard had created his machine by combining two earlier French
inventors' ideas: he applied Jean Falcon's chain of punched cards to the cylinder
mechanism of Jacques Vaucanson. Then he mounted his device on top of a treadleoperated loom. This was the earliest use of punched cards programmed to contral a
manufacturing process. Although he created his mechanism to aid the local silk
industry, it was soon applied to cotton, wool, and linen weaving. It appeared in the
United States about 1825 or 1826. William Horstmann, the owner of a Philadelphia
firm, may have introduced it here for weaving coach laces. Erastus Bigelow was
issued the first patent for a Jacquard power loom in 1842. He used the loom for
ingrain carpet weaving."
Babbage’s Analytical Engine
http://www.cbi.umn.edu/
http://www.fourmilab.ch/babbage/
http://www.ex.ac.uk/BABBAGE/
http://ei.cs.vt.edu/~history/Babbage.html
http://hoc.co.umist.ac.uk/storylines/compdev/earlymechanical/analytengine.html
Difference Engine
http://hoc.co.umist.ac.uk/storylines/compdev/earlymechanical/diffengine.html
Although the Difference Engine was very important in the development of
computation, the Analytical Engine was revolutionary. It was the first example
of a machine being directed by an external program. This arose from the idea
that the contents of the result wheel could be fed back in to the difference
wheels, thereby allowing the automatic calculation of tables whose contents
had no elementary analytical solution.
As he thought this problem over, he began to grasp the concept of the
mechanical registers all being identical, autonomous units. Rather than just
adding their quantities to their neighbours, they could be thought of as stores
for numbers. These numbers could even be simply passed from register to
register without any arithmetic done on the values. His letter of May 1835 to
Mr. Quetelet shows the impact of the revelation occurring to him, in which he
says he had...
"...for six months been engaged in making the drawings of a new calculating
engine of far greater power than the first. I am myself astonished at the power
I have been enabled to give this machine; a year ago I should not have believed
this result possible."
The design of this machine was to remain an academic exercise, Babbage
apparently satisfying himself with the design and redesign of the machine until
his death. Despite this, it is apparent from the design that he is designing it
with construction in mind, as many components were clearly designed to be
produced without undue difficulty.
A birds eye view of a design near to the final version is shown below. This
shows the number stores similar to the Difference Engine, along with the
numerous detailed control axles involved. The various components can be split
down into the store, the mill and he control barrel, which correspond to the
memory, the arithmetic unit and the program control unit respectively. The
number stores can be expanded, and in Babbage's literature he refers to systems
with 100 40 digit numbers and ones with 1000 50 digit numbers. The mill
consists of three main registers, two to contain operands, and one for
housekeeping jobs related to multiplication etc. It also contains 9 table axes for
intermediate results in multiplication and division.
The control barrels had the routines for the various operations on it in such a
way that the studs pushed on different sets of control rods to engage or
disengage the levers and gear trains that were necessary to implement different
instruction sets. The control barrel had the additional capacity of controlling its
own action to execute different operations. Each step on the barrel therefore
was similar to an instruction of today, with the address of the next instruction
coded in the current instruction.
Another facility was a counter register, which was intended to count the
number of iterations of a particular operation, (the number of times it had been
performed). This relates directly to the loop counters frequently used in today's
programming languages.
A notable advance was also made in dealing with propagating carries, which
originally required an additional operation. This was done with a novel
mechanical system whereby the carry digit bypasses all the numbers set to 9, to
arrive straight at the first number it can be added to. This anticipating carriage
allowed carries to be propagated regardless of the distance they have to cover.
Analogies of this method were used in some early electrical accounting
machines too.
As if this wasn't enough, it also used punched cards to input it's programs, an
idea Babbage took from the automatic Jacquard loom, which loaded its patterns
from punched cards. They could not only include basic instructions but also
conditional and non-conditional branches and loops. This meant the machine
was easily capable of carrying out any calculations Babbage could ever require
of it. Babbage also conceived the potential for multiple card readers for
program, data and function values. These are all concepts that were repeatedly
used in the field for well over 100 years.
Babbage's Lithograph of the Analytical Engine
The final machine was capable of additions in about 1 second, and
multiplications would take approximately 1 minute. Even 100 years later, as
will be seen, the mechanical Harvard Mark I would take 0.3 of a second for an
addition.
The final machine would take up a space of 15 by 6 by 10 to 20 feet, depending
on the number of numbers it incorporated. The tolerance of the components
would
have to be within 1 / 500 of
an inch, which although
possible at that time, would
be very expensive.
The Analytical Engine
However, in 1906 the actual
construction was completed
by his son, Major Henry
Babbage, with help from a
local engineering firm. The
first program was to
calculate and print the first
25 multiples of pi to 29
decimal places, to
demonstrate that it worked.
This machine is now housed
along with several other
Babbage machines in the
Science museum in London,
a photo of which can be seen
here. The basic design was
copied to a large degree in
the later Harvard Mark 1
machine, which was itself
almost exactly duplicated
electronically in the ENIAC.
Ada Augusta Lovelace (nee Byron)
"Sketch of the Analytical Engine" by L. F. Menabrea, translated and with
extensive commentary by Ada Augusta, Countess of Lovelace. This 1842
document is the definitive exposition of the Analytical Engine, which
described many aspects of computer architecture and programming more than
a hundred years before they were "discovered" in the twentieth century. If you
have ever doubted, even for a nanosecond, that Lady Ada was, indeed, the
First Hacker, perusal of this document will demonstrate her primacy beyond a
shadow of a doubt.
http://www.ex.ac.uk/BABBAGE/ada.html
In 1833 Ada met Babbage and was fascinated with both him and his Engines.
Later Ada became a competent student of mathematics, which was most
unusual for a woman at the time. She translated a paper on Babbage's Engines
by General Menabrea, later to be prime minister of the newly united Italy.
Under Babbage's careful supervision Ada added extensive notes (c.f. Science
and Reform, Selected Works of Charles Babbage, by Anthony Hyman) which
constitute the best contemporary description of the Engines, and the best
account we have of Babbage's views on the general powers of the Engines.
Beautiful, charming, temperamental, an aristocratic hostess, mathematicians of
the time thought her a magnificent addition to their number.
It is often suggested that Ada was the world's first programmer. This is
nonsense: Babbage was, if programmer is the right term. After Babbage came
a mathematical assistant of his, Babbage's eldest son, Herschel, and possibly
Babbage's two younger sons. Ada was probably the fourth, fifth or six person
to write the programmes. Moreover all she did was rework some calculations
Babbage had carried out years earlier. Ada's calculations were student
exercises. Ada Lovelace figures in the history of the Calculating Engines as
Babbage's interpretress, his `fairy lady'. As such her achievement was
remarkable.
http://historia.et.tudelft.nl/wggesch/geschiedenis/computer/
Herman Hollerith
http://www.maxmon.com/punch1.htm
The first practical use of punched cards for data processing is credited to
the American inventor Herman Hollerith, who decided to use Jacquard's
punched cards to represent the data gathered for the American census of
1890, and to read and collate this data using an automatic machine.
a
Many references state that Hollerith
originally made his punched cards the
same size as the dollar bills of that era,
because he realized that it would be
convenient and economical to buy
existing office furniture, such as desks
and cabinets, that already contained
receptacles to accommodate stacks of
bills. Other sources consider this to be a
popular fiction. Whatever the case, we do
know that these cards were eventually
standardized at 7 and 3/8 inches by 3
and 1/4 inches, and Hollerith's many
patents permitted his company (which
became International Business Machines
(IBM) in 1924) to hold an effective
monopoly on punched cards for many
years.
Herman Hollerith
Copyright (c) 1997. Maxfield & Montrose Interactive Inc
a
Hollerith, who was no one's fool, had quickly realized that the real money
was not to be made in the tabulating machines themselves, but rather in the
tens or hundreds of thousands of cards that were used to store data.
Although other companies came up with innovative ways to bypass
Hollerith's patents, they failed to capitalize on their advances, thereby giving
IBM a chance to regain the high ground.
a
For example, Hollerith's early
This set the standard until 1924-
cards were punched with round
holes, because his prototype
machine employed cards with
holes created using a tram
conductor's ticket punch.
1925, when the Remington Rand
Corporation evolved a technique for
doubling the amount of information
that could be stored on each card.
But they failed to exploit this
advantage to its fullest extent, and,
in 1929-1931, IBM responded by
using rectangular holes, which
allowed them to pack 80 columns of
data onto each card. Although other
formats appeared sporadically
(including some from IBM), the 80
column card shown above
overwhelmingly dominated the
punched card market from around
the 1950s onward.
Hollerith continued to use round
holes in his production machines,
which effectively limited the
amount of data that could be
stored on each card. By the early
1900s, Hollerith's cards
supported 45 columns, where
each column could be used to
represent a single character or
data value.
a
The figure to the left shows one of
IBM 80-column punched card format
the early 80 column IBM cards (not
to scale). Each card contains 12
rows of 80 columns, and each
column is typically used to
represent a single piece of data
such as a character. The top row is
called the "12" or "Y" row; the
second row from the top is called
the "11" or "X" row; and the
remaining rows are called the "0" to
"9" rows (indicated by the numbers
printed on the cards).
a
This figure (which took one heck of a long time to draw let me tell you)
illustrates one of the early, simpler coding schemes, in which each character
could be represented using no more than three holes. (Note that we haven't
shown all of the different characters that could be represented). Over the
course of time, more sophisticated coding schemes were employed to allow
these cards to represent different character sets such as ASCII and
EBCDIC; the rows and columns stayed the same, but different combinations
of holes were used.
a
One advantage of punched
Although punched cards are
cards over paper tapes was that
the textual equivalent of the
patterns of holes could be printed
along the top of the card (one
character above each column).
Another advantage was that it
was easy to replace any cards
containing errors. However, the
major disadvantage of working
off-line (with both punched cards
and paper tapes) was that the
turn-around time to actually
locate and correct any errors was
horrendous.
rarely used now, we endure their
legacies to this day. For example,
the first computer monitors were
constructed so as to display 80
characters across the screen. This
number was chosen on the basis
that you certainly wouldn't want to
display fewer characters than were
on an IBM punched card, and there
didn't appear to be any obvious
advantage to being able to display
more characters than were on a
card (see also John Vincent
Atanasoff's burnt offerings).
a
MIT Differential Analyzer
http://web.mit.edu/mindell/www/analyzer.htm
http://www.coe.uh.edu/courses/cuin7317/students/museum/bbrown.html
Atanasoff-Berry Computer
http://www.ieee.org/organizations/history_center/milestones_photos/atanasoff.ht
ml
John Vincent Atanasoff conceived basic design principles for the first electronic-digital
computer in the winter of 1937 and, assisted by his graduate student, Clifford E. Berry,
constructed a prototype here in October 1939. It used binary numbers, direct logic for
calculation, and a regenerative memory. It embodied concepts that would be central to the
future development of computers.
"It was at an evening of bourbon and 100 mph car rides," Atanasoff said, "when the concept
came, for an electronically operated machine, that would use base-two (binary) numbers
instead of the traditional base-10 numbers, condensers for memory, and a regenerative
process to preclude loss of memory from electrical failure.”
Atanasoff wrote most of the concepts of the first modern computer on the back of a cocktail
napkin.
Then, in late 1939, John V. Atanasoff teamed up with Clifford E. Berry to build a prototype.
They created the first computing machine to use electricity, vacuum tubes, binary numbers
and capacitors. The capacitors were in a rotating drum that held the electrical charge for the
memory. Berry, with his background in electronics and mechanical construction skills, was
the ideal partner for Atanasoff. The prototype won the team a grant of $850 to build a fullscale model. They spent the next two years further improving the Atanasoff-Berry Computer
(aka ABC). The final product was the size of a desk, weighed 700 pounds, had over 300
vacuum tubes, and contained a mile of wire. It could calculate about one operation every 15
seconds, today a computer can calculate 150 billion operations in 15 seconds. Too large to
go anywhere, it remained in the basement of the physics department. The war effort
prevented Atanasoff from finishing the patent process and doing any further work on the
computer. When they needed storage space in the physics building, they dismantled the
Atanasoff-Berry Computer.
Alan Turing
http://www.turing.org.uk/turing/
Biography: Alan Turing: the enigma, by Alan Hodges
http://ei.cs.vt.edu/~history/Turing.html
Konrad Zuse
http://irb.cs.tu-berlin.de/~zuse/Konrad_Zuse/en/Rechner_Z1.html
Computer Generations
history.acusd.edu/gen/recording/ computer1.html
Moore’s Law
http://www.intel.com/research/silicon/mooreslaw.htm
Gordon Moore made his famous observation in 1965, just four
years after the first planar integrated circuit was discovered.
The press called it "Moore's Law" and the name has stuck. In
his original paper, Moore observed an exponential growth in
the number of transistors per integrated circuit and predicted
that this trend would continue. Through Intel's relentless
technology advances, Moore's Law, the doubling of transistors
every couple of years, has been maintained, and still holds true
today. Intel expects that it will continue at least through the end
of this decade. The mission of Intel's technology development
team is to continue to break down barriers to Moore's Law.
4004
8008
8080
8086
286
386™ processor
486™ DX processor
Pentium®
processor
Pentium II
processor
Pentium III
processor
Pentium 4
processor
Year of introduction
1971
1972
1974
1978
1982
1985
1989
Transistors
2,250
2,500
5,000
29,000
120,000
275,000
1,180,000
1993
3,100,000
1997
7,500,000
1999
24,000,000
2000
42,000,000
Gordon Moore made his famous observation in 1965, just four
years after the first planar integrated circuit was discovered.
The press called it "Moore's Law" and the name has stuck. In
his original paper, Moore observed an exponential growth in
the number of transistors per integrated circuit and predicted
that this trend would continue. Through Intel's relentless
technology advances, Moore's Law, the doubling of transistors
every couple of years, has been maintained, and still holds true
today. Intel expects that it will continue at least through the end
of this decade. The mission of Intel's technology development
team is to continue to break down barriers to Moore's Law.
The History of the Computer
The earliest computing instrument is the 'abacus', which was first used 2,000
years ago. It is a simple wooden rach holding parallel wires on which beads are
strung. These beads can be moved along the wire helping the user to calculate
ordinary arithmetic operations.
In 1642 Blaise Pascal built the first "digital calculating machine". It could add
numbers that were entered into the machine using dials. Pascal initially built it
to help his father, who was a tax collector. Gottfried Wilhelm von Liebniz in
1671 invented a computer that could add and multiply. Multiplication was done
by successive adding and shifting. This computer was built in 1694, and used a
special "stepped gear" mechanism (which is still in use) for introducing the
addend digits. Although the prototypes built by Leibniz and Pascal were not
widely used, they remained curiosities until more than a century later, when
Tomas of Colmar (Charles Xavier Thomas) developed the first commercially
successful mechanica calculater in 1820. This calculator was capable of adding,
subtracting, multiplying and deviding. By the 1890 the caclulator had developed
into an apparatus that could accumulate results, store them and print them.
Charles Babbage realized (1812) that many long computations, especially those
needed to prepare mathematical tables, consisted of routine operations that were
regularly repeated; from this he surmised that it ought to be possible to do these
operations automatically. He began to design an automatic mechanical
calculating machine, which he called a "difference engine," and by 1822 he had
built a small working model for demonstration. With financial help from the
British government, Babbage started construction of a full-scale difference
engine in 1823. It was intended to be steam-powered; fully automatic, even to the
printing of the resulting tables; and commanded by a fixed instruction program.
Charles Babbage (1792-1871)
(National Portrait Gallery, London)
The difference engine, although of limited flexibility and applicability, was
conceptually a great advance. Babbage continued work on it for 10 years, but in
1833 he lost interest because he had a "better idea" --the construction of what
today would be described as a general-purpose, fully program-controlled,
automatic mechanical digital computer. Babbage called his machine an
"analytical engine"; the characteristics aimed at by this design show true
prescience, although this could not be fully appreciated until more than a
century later. The plans for the analytical engine specified a parallel decimal
computer operating on numbers (words) of 50 decimal digits and provided with
a storage capacity (memory) of 1,000 such numbers. Built-in operations were to
include everything that a modern general-purpose computer would need, even
the all-important "conditional control transfer" capability, which would allow
instructions to be executed in any order, not just in numerical sequence. The
analytical engine was to use a punched card (similar to that used on a Jacquard
loom), which was to be read into the machine from any of several reading
stations. The machine was designed to operate automatically, by steam power,
and it would require only one attendant.
Babbage's computers were never completed. Various reasons are advanced for
his failure, most frequently the lack of precision machining techniques at the
time. Another conjecture is that Babbage was working on the solution of a
problem that few people in 1840 urgently needed to solve.
Babbage's Difference Engine (1833)
(The Bettmann Archive)
After Babbage there was a temporary loss of interest in automatic digital
computers. Between 1850 and 1900 great advances were made in mathematical
physics, and it came to be understood that most observable dynamic phenomena
can be characterized by differenctial equations, so that ready means for their
solution and for the solution of other problems of calculus would be helpful.
Moreover, from a practical standpoint, the availability of steam power caused
manufacturing, transportation, and commerce to thrive and led to a period of
great engineering achievement. The designing of railroads and the construction
of steamships, textile mills, and bridges required differential calculus to
determine such quantities as centers of gravity, centers of buoyancy, moments of
inertia, and stress distributions; even the evaluation of the power output of a
steam engine required practical mathematical integration. A strong need thus
developed for a machine that could rapidly perform many repetitive
calculations.
A step toward automated computation was the introduction of punched cards,
which were first successfully used in connection with computing in 1890 by
Herman Hollerith and James Powers, working for the U.S. Census Bureau. They
developed devices that could automatically read the information that had been
punched into cards, without human intermediation. Reading errors were
consequently greatly reduced, work flow was increased, and, more important,
stacks of punched cards could be used as an accessible memory store of almost
unlimited capacity; furthermore, different problems could be stored on different
batches of cards and worked on as needed.
Herman Hollerith (1860-1929)
(The Bettmann Archive)
These advantages were noted by commercial interests and soon led to the
development of improved punch-card business-machine systems by International
Business Machines (IBM), Remington-Rand, Burroughs, and other corporations.
These systems used electromechanical devices, in which electrical power
provided mechanical motion--such as for turning the wheels of an adding
machine. Such systems soon included features to feed in automatically a specified
number of cards from a "read-in" station; perform such operations as addition,
multiplication, and sorting; and feed out cards punched with results. By modern
standards the punched-card machines were slow, typically processing from 50 to
250 cards per minute, with each card holding up to 80 decimal numbers. At the
time, however, punched cards were an enormous step forward.
By the late 1930s punched-card machine techniques had become well established
and reliable, and several research groups strove to build automatic digital
computers. One promising machine, constructed of standard electromechanical
parts, was built by an IBM team led by Howard Hathaway Aiken. Aiken's
machine, called the Harvard Mark I, handled 23-decimal-place numbers (words)
and could perform all four arithmetic operations. Moreover, it had special builtin programs, or subroutines, to handle logarithms and trigonometric functions.
The Mark I was originally controlled from prepunched paper tape without
provision for reversal, so that automatic "transfer of control" instructions could
not be programmed. Output was by card punch and electric typewriter.
Although the Mark I used IBM rotating counter wheels as key components in
addition to electromagnetic relays, the machine was classified as a relay
computer. It was slow, requiring 3 to 5 seconds for a multiplication, but it was
fully automatic and could complete long computations. Mark I was the first of a
series of computers designed and built under Aiken's direction.
Electronic Digital Computers
The outbreak of World War II produced a desperate need for computing
capability, especially for the military. New weapons systems were produced for
which trajectory tables and other essential data were lacking. In 1942, J. Presper
Eckert, John W. Mauchly, and their associates at the Moore School of Electrical
Engineering of the University of Pennsylvania decided to build a high-speed
electronic computer to do the job. This machine became known as ENIAC, for
Electronic Numerical Integrator and Computer (or Calculator).The size of its
numerical word was 10 decimal digits, and it could multiply two such numbers
at the rate of 300 products per second, by finding the value of each product from
a multiplication table stored in its memory. Although difficult to operate, ENIAC
was still many times faster than the previous generation of relay computers.
ENIAC, the first high-speed electronic computer.
(The Bettmann Archive)
ENIAC used 18,000 standard vacuum tubes, occupied 167.3 sq m (1,800 sq ft) of
floor space, and consumed about 180,000 watts of electrical power. It had
punched-card input and output and arithmetically had 1 multiplier, 1 dividersquare rooter, and 20 adders employing decimal "ring counters," which served
as adders and also as quick-access (0.0002 seconds) read-write register storage.
The executable instructions composing a program were embodied in the separate
units of ENIAC, which were plugged together to form a route through the
machine for the flow of computations. These connections had to be redone for
each different problem, together with presetting function tables and switches.
This "wire-your-own" instruction technique was inconvenient, and only with
some license could ENIAC be considered programmable; it was, however,
efficient in handling the particular programs for which it had been designed.
ENIAC is generally acknowledged to be the first successful high-speed electronic
digital computer (EDC) and was productively used from 1946 to 1955. A
controversy developed in 1971, however, over the patentability of ENIAC's basic
digital concepts, the claim being made that another U.S. physicist, John v.
Atanasoff, had already used the same ideas in a simpler vacuum-tube device he
built in the 1930s at Iowa State College. In 1973 the court found in favor of the
company using the Atanasoff claim.
Intrigued by the success of ENIAC, the mathematician John von Neumann
undertook (1945) a theoretical study of computation that demonstrated that a
computer could have a very simple, fixed physical structure and yet be able to
execute any kind of computation effectively by means of proper programmed
control without the need for any changes in hardware. Von Neumann
contributed a new understanding of how practical fast computers should be
organized and built; these ideas, often referred to as the stored-program
technique, became fundamental for future generations of high-speed digital
computers.
John von Neumann (1903-57)
(The Bettmann Archive)
The stored-program technique involves many features of computer design and
function besides the one named; in combination, these features make very-highspeed operation feasible. Details cannot be given here, but a glimpse may be
provided by considering what 1,000 arithmetic operations per second implies. If
each instruction in a job program were used only once in consecutive order, no
human programmer could generate enough instructions to keep the computer
busy. Arrangements must be made, therefore, for parts of the job program
called subroutines to be used repeatedly in a manner that depends on how the
computation progresses. Also, it would clearly be helpful if instructions could be
altered as needed during a computation to make them behave differently. Von
Neumann met these two needs by providing a special type of machine instruction
called conditional control transfer--which permitted the program sequence to be
interrupted and reinitiated at any point--and by storing all instruction programs
together with data in the same memory unit, so that, when desired, instructions
could be arithmetically modified in the same way as data.
As a result of these techniques and several others, computing and programming
became faster, more flexible, and more efficient, with the instructions in
subroutines performing far more computational work. Frequently used
subroutines did not have to be reprogrammed for each new problem but could
be kept intact in "libraries" and read into memory when needed. Thus, much of
a given program could be assembled from the subroutine library. The allpurpose computer memory became the assembly place in which parts of a long
computation were stored, worked on piecewise, and assembled to form the final
results. The computer control served as an errand runner for the overall process.
As soon as the advantages of these techniques became clear, the techniques
became standard practice.
The first generation of modern programmed electronic computers to take
advantage of these improvements appeared in 1947. This group included
computers using random access memory (RAM), which is a memory designed to
give almost constant access to any particular piece of information. These
machines had punched-card or punched-tape input and output devices and
RAMs of 1,000-word capacity with an access time of 0.5 microseconds (0.5 x 10
to the power of minus 6 seconds); some of them could perform multiplications in
2 to 4 microseconds. Physically, they were much more compact than ENIAC:
some were about the size of a grand piano and required 2,500 small electron
tubes, far fewer than required by the earlier machines. The first-generation
stored-program computers required considerable maintenance, attained perhaps
70 percent to 80 percent reliable operation, and were used for 8 to 12 years.
Typically, they were programmed directly in machine language, although by the
mid-1950s progress had been made in several aspects of advanced programming.
This group of machines included EDVAC and UNIVAC (see UNIVAC), the first
commercially available computers.
UNIVAC computer, 1955
(The Bettmann Archive)
Early in the 1950s two important engineering discoveries changed the image of
the electronic-computer field, from one of fast but often unreliable hardware to
an image of relatively high reliability and even greater capability. These
discoveries were the magnetic-core memory and the transistor-circuit element.
These new technical discoveries rapidly found their way into new models of
digital computers; RAM capacities increased from 8,000 to 64,000 words in
commercially available machines by the early 1960s, with access times of 2 or 3
msec. These machines were very expensive to purchase or to rent and were
especially expensive to operate because of the cost of expanding programming.
Such computers were typically found in large computer centers--operated by
industry, government, and private laboratories--staffed with many programmers
and support personnel. This situation led to modes of operation enabling the
sharing of the high capability available; one such mode is batch processing, in
which problems are prepared and then held ready for computation on a
relatively inexpensive storage medium, such as magnetic drums, magnetic-disk
packs, or magnetic tapes. When the computer finishes with a problem, it
typically "dumps" the whole problem--program and results--on one of these
peripheral storage units and takes in a new problem. Another mode of use for
fast, powerful machines is called TIME-SHARING. In time-sharing the
computer processes many waiting jobs in such rapid succession that each job
progresses as quickly as if the other jobs did not exist, thus keeping each
customer satisfied. Such operating modes require elaborate "executive"
programs to attend to the administration of the various tasks.
In the 1960s efforts to design and develop the fastest possible computers with the
greatest capacity reached a turning point with the completion of the LARC
machine for Livermore Radiation Laboratories of the University of California by
the Sperry-Rand Corporation, and the Stretch computer by IBM. The LARC
had a core memory of 98,000 words and multiplied in 10 msec. Stretch was
provided with several ranks of memory having slower access for the ranks of
greater capacity, the fastest access time being less than 1 msec and the total
capacity in the vicinity of 100 million words.
During this period the major computer manufacturers began to offer a range of
computer capabilities and costs, as well as various peripheral equipment--such
input means as consoles and card feeders; such output means as page printers,
cathode-ray-tube displays, and graphing devices; and optional magnetic-tape
and magnetic-disk file storage. These found wide use in business for such
applications as accounting, payroll, inventory control, ordering supplies, and
billing. Central processing units (CPUs) for such purposes did not need to be
very fast arithmetically and were primarily used to access large amounts of
records on file, keeping these up to date. By far the greatest number of computer
systems were delivered for the more modest applications, such as in hospitals for
keeping track of patient records, medications, and treatments given. They are
also used in automated library systems, such as MEDLARS, the National
Medical Library retrieval system, and in the Chemical Abstracts system, where
computer records now on file cover nearly all known chemical compounds.
The trend during the 1970s was, to some extent, away from extremely powerful,
centralized computational centers and toward a broader range of applications
for less-costly computer systems. Most continuous-process manufacturing, such
as petroleum refining and electrical-power distribution systems, now use
computers of relatively modest capability for controlling and regulating their
activities. In the 1960s the programming of applications problems was an
obstacle to the self-sufficiency of moderate-sized on-site computer installations,
but great advances in applications programming languages are removing these
obstacles. Applications languages are now available for controlling a great range
of manufacturing processes, for computer operation of machine tools, and for
many other tasks.
Moreover, a new revolution in computer hardware came about, involving
miniaturization of computer-logic circuitry and of component manufacture by
what are called large-scale integration, or LSI, techniques. In the 1950s it was
realized that "scaling down" the size of electronic digital computer circuits and
parts would increase speed and efficiency and thereby improve performance--if
only manufacturing methods were available to do this. About 1960 photoprinting
of conductive circuit boards to eliminate wiring became highly developed. Then
it became possible to build resistors and capacitors into the circuitry by
photographic means (printed circuit boards). In the 1970s vacuum deposition of
transistors became common, and entire assemblies, such as adders, shifting
registers, and counters, became available on tiny "chips." In the 1980s very
large-scale integration (VLSI), in which hundreds of thousands of transistors are
placed on a single chip, became increasingly common. Many companies, some
new to the computer field, introduced in the 1970s the programmable
minicomputer supplied with software packages. The size-reduction trend
continued with the introduction of personal computers, which are
programmable machines small enough and inexpensive enough to be purchased
and used by individuals. Many companies, such as Apple Computer and Radio
Shack, introduced very successful personal computers in the 1970s. Augmented
in part by a fad in computer, or video, games, development of these small
computers expanded rapidly.
In the 1980s the enormous success of the personal computer and resultant
advances in microprocessor technology initiated a process of attrition among
giants of the computer industry. That is, as a result of advances continually being
made in the manufacture of chips, rapidly increasing amounts of computing
power could be purchased for the same basic costs. Microprocessors equipped
with ROM, or read-only memory (which stores constantly used, unchanging
programs), now were also performing an increasing number of process-control,
testing, monitoring, and diagnosing functions, as in automobile ignition systems,
automobile-engine diagnosis, and production-line inspection tasks. By the early
1990s these changes were forcing the computer industry as a whole to make
striking adjustments. Long-established and more recent giants of the field--most
notably, such companies as IBM, Digital Equipment Corporation, and Italy's
Olivetti--were reducing their work staffs, shutting down factories, and dropping
subsidiaries. At the same time, producers of personal computers continued to
proliferate and specialty companies were emerging in increasing numbers, each
company devoting itself to some special area of manufacture, distribution, or
customer service. These trends will probably continue for the foreseeable future.
Computers continue to dwindle to increasingly convenient sizes for use in offices,
schools, and homes. Programming productivity has not increased as rapidly, and
as a result software has become the major cost of many systems. New
programming techniques such as object-oriented programming, however, have
been developed to help alleviate this problem. The computer field as a whole
continues to experience tremendous growth. As computer and
telecommunications technologies continue to integrate, computer networking,
computer mail, and electronic publishing are just a few of the applications that
have matured in recent years.
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