History of computers

What are computers?
 The first computers were people!
 That is, electronic computers (and the earlier
mechanical computers) were given this name
because they performed the work that had
previously been assigned to people.
 "Computer" was originally a job title: it was used to
describe those human beings (predominantly
women) whose job it was to perform the repetitive
calculations

Abacus
 The abacus was an early aid
for mathematical
computations.
 Its only value is that it aids the
memory of the human
performing the calculation.
 A skilled abacus operator can
work on addition and
subtraction problems at the
speed of a person equipped
with a hand calculator
(multiplication and division are
slower).

Abacus
 The abacus is often
wrongly attributed to
China.
 In fact, the oldest
surviving abacus was
used in 300 B.C. by
the Babylonians.
 The abacus is still in
use today, principally
in the far east.

John Napier
 In 1617 an eccentric (some say mad) Scotsman
named John Napier invented logarithms
 which are a technology that allows multiplication
to be performed via addition.

Napier’s Bones
 The magic ingredient is
the logarithm of each
operand, which was
originally obtained from a
printed table.
 But Napier also invented
an alternative to tables,
where the logarithm
values were carved on
ivory sticks which are
now called Napier's
Bones.

Slide Rule
 Napier's invention led directly to the slide rule,
first built in England in 1632 and still in use in the
1960's by the NASA engineers of the Mercury,
Gemini, and Apollo programs which landed men
on the moon.

Leonardo da Vinci
 Leonardo da Vinci (1452-1519) made drawings
of gear-driven calculating machines but
apparently never built any.

Calculating Clock
 The first gear-driven
calculating machine to
actually be built was
probably the calculating
clock, so named by its
inventor, the German
professor Wilhelm
Schickard in 1623.
 This device got little
publicity because
Schickard died soon
afterward in the bubonic
plague.

Blaise Pascal
 In 1642 Blaise Pascal, at age 19, invented the Pascaline
as an aid for his father who was a tax collector. Pascal
built 50 of this gear-driven one-function calculator (it
could only add) but couldn't sell many because of their
exorbitant cost and because they really weren't that
accurate (at that time it was not possible to fabricate
gears with the required precision).
 Up until the present age when car dashboards went
digital, the odometer portion of a car's speedometer
used the very same mechanism as the Pascaline to
increment the next wheel after each full revolution of the
prior wheel.

Charle’s Babbage
 By 1822 the English
mathematician Charles
Babbage was
proposing a steam
driven calculating
machine the size of a
room, which he called
the Difference Engine.

Difference Engine
 This machine would be able to compute tables of
numbers, such as logarithm tables.
 He obtained government funding for this project due to
the importance of numeric tables in ocean navigation.
 Construction of Babbage's Difference Engine proved
exceedingly difficult and the project soon became the
most expensive government funded project up to that
point in English history.
 Ten years later the device was still nowhere near
complete, acrimony abounded between all involved, and
funding dried up. The device was never finished.

Babbage-Analytic Engine
 Babbage was not deterred, and by then was on to
his next brainstorm, which he called the Analytic
Engine.
 This device, large as a house and powered by 6
steam engines,
 It was programmable, thanks to the punched card
technology of Jacquard.
 Babbage saw that the pattern of holes in a punch
card could be used to represent an abstract idea
such as a problem statement or the raw data
required for that problem's solution.

Babbage-Analytic Engine
 Babbage realized that punched paper could be
employed as a storage mechanism, holding
computed numbers for future reference.
 Because of the connection to the Jacquard loom,
Babbage called the two main parts of his Analytic
Engine the "Store" and the "Mill", as both terms are
used in the weaving industry.
 The Store was where numbers were held and the
Mill was where they were "woven" into new results.
 In a modern computer these same parts are called
the memory unit and the central processing unit
(CPU).

Babbage – Analytic Engine
 The Analytic Engine also had a key function
that distinguishes computers from
calculators: the conditional statement.
 A conditional statement allows a program to
achieve different results each time it is run.
 Based on the conditional statement, the path
of the program can be determined based
upon a situation that is detected at the very
moment the program is running.

Ada Byron
 Babbage befriended Ada Byron, the daughter of
the famous poet Lord Byron
 Though she was only 19, she was fascinated by
Babbage's ideas
 She began fashioning programs for the Analytic
Engine, although still unbuilt.
 The Analytic Engine remained unbuilt (the British
government refused to get involved with this one)
but Ada earned her spot in history as the first
computer programmer.
 Ada invented the subroutine and was the first to
recognize the importance of looping.

US Census
 The next breakthrough occurred in America. The
U.S. Constitution states that a census should be
taken of all U.S. citizens every 10 years in order to
determine the representation of the states in
Congress.
 While the very first census of 1790 had only required
9 months, by 1880 the U.S. population had grown
so much that the count for the 1880 census took 7.5
years. Automation was clearly needed for the next
census.
 The census bureau offered a prize for an inventor to
help with the 1890 census and this prize was won
by Herman Hollerith,

IBM
 Hollerith built a
company, the
Tabulating Machine
Company which, after a
few buyouts, eventually
became International
Business Machines,
known today as IBM.

US Military
 The U.S. military desired a mechanical calculator
more optimized for scientific computation.
 By World War II the U.S. had battleships that could
lob shells weighing as much as a small car over
distances up to 25 miles.
 Physicists could write the equations that described
how atmospheric drag, wind, gravity, muzzle
velocity, etc. would determine the trajectory of the
shell, but solving such equations was extremely
laborious.

US Military
 Human computers would compute results of these
equations and publish them in ballistic "firing tables"
 During World War II the U.S. military scoured the country
looking for (generally female) math majors to hire for the
job of computing these tables, but not enough humans
could be found to keep up with the need for new tables.
 Sometimes artillery pieces had to be delivered to the
battlefield without the necessary firing tables and this
meant they were close to useless because they couldn't be
aimed properly.
 Faced with this situation, the U.S. military was willing to
invest in even hair-brained schemes to automate this type
of computation.

Mark I
 One early success was the
Harvard Mark I computer
which was built as a
partnership between
Harvard and IBM in 1944.
 This was the first
programmable digital
computer made in the U.S.
 But it was not a purely
electronic computer.
Instead the Mark I was
constructed out of switches,
relays, rotating shafts, and
clutches.

Mark I
 The machine weighed 5
tons, incorporated 500
miles of wire, was 8 feet tall
and 51 feet long, and had a
50 ft rotating shaft running
its length, turned by a 5
horsepower electric motor.
 The Mark I ran non-stop for
15 years, sounding like a
roomful of ladies knitting.

The First Bug
 One of the primary
programmers for the Mark I
was a woman, Grace Hopper.
 Hopper found the first
computer "bug": a dead moth
that had gotten into the Mark I
 The word "bug" had been used
to describe a defect since at
least 1889 but Hopper is
credited with coining the word
"debugging" to describe the
work to eliminate program
faults.

Humor
 On a humorous note, the principal designer
of the Mark I, Howard Aiken of Harvard,
estimated in 1947 that six electronic digital
computers would be sufficient to satisfy the
computing needs of the entire United States.

The Future of Computers?
 IBM had commissioned this study to determine
whether it should bother developing this new
invention into one of its standard products (up until
then computers were one-of-a-kind items built by
special arrangement).
 Aiken's prediction wasn't actually so bad as there
were very few institutions (principally, the
government and military) that could afford the cost
of what was called a computer in 1947.
 He just didn't foresee the micro-electronics
revolution which would allow something like an IBM
Stretch computer of 1959:

First Generation Computers
 The first electronic computer was designed at
Iowa State between 1939-1942
 The Atanasoff-Berry Computer used the
binary system(1’s and 0’s).
 Contained vacuum tubes and stored numbers
for calculations by burning holes in paper

Eniac
 The title of forefather of today's all-electronic digital
computers is usually awarded to ENIAC, which
stood for Electronic Numerical Integrator and
Calculator.
 ENIAC was built at the University of Pennsylvania
between 1943 and 1945 by two professors, John
Mauchly and the 24 year old J. Presper Eckert,
who got funding from the war department after
promising they could build a machine that would
replace all the "computers”
 ENIAC filled a 20 by 40 foot room, weighed 30 tons,
and used more than 18,000 vacuum tubes.

Programming the ENIAC
 To reprogram the ENIAC you had to rearrange the
patch cords that you can observe on the left in the
prior photo, and the settings of 3000 switches that
you can observe on the right.
 To program a modern computer, you type out a
program with statements like:
 Circumference = 3.14 * diameter
 To perform this computation on ENIAC you had to
rearrange a large number of patch cords and then
locate three particular knobs on that vast wall of
knobs and set them to 3, 1, and 4.

Problems with the ENIAC
 The ENIAC used 18,000 vacuum tubes to
hold a charge
 Vacuum tubes were so notoriously unreliable
that even twenty years later many
neighborhood drug stores provided a "tube
tester"

The Stored Program Computer
 In 1945 John von Neumann presented his
idea of a computer that would store computer
instructions in a CPU
 The CPU(Central Processing Unit) consisted
of elements that would control the computer
electronically

The Stored Program Computer
 The EDVAC, EDSAC and UNIVAC were the
first computers to use the stored program
concept
 They used vacuum tubes so they were too
expensive and too large for households to
own and afford

Edvac
 It took days to change
ENIAC's program.
 Eckert and Mauchly's next
teamed up with the
mathematician John von
Neumann to design
EDVAC, which pioneered
the stored program.
 After ENIAC and EDVAC
came other computers with
humorous names such as
ILLIAC, JOHNNIAC, and,
of course, MANIAC

Second Generation Computers
 In 1947, the transistor was invented
 The transistor made computers smaller, less
expensive and increased calculating speeds.
 Second generation computers also saw a new way
data was stored
 Punch cards were replaced with magnetic tapes and
reel to reel machines

Univac
 The UNIVAC computer was
the first commercial (mass
produced) computer.
 In the 50's, UNIVAC (a
contraction of "Universal
Automatic Computer") was
the household word for
"computer" just as
"Kleenex" is for "tissue".
 UNIVAC was also the first
computer to employ
magnetic tape.

Third Generation Computers
 Transistors were replaced
by integrated circuits(IC)
 One IC could replace
hundreds of transistors
 This made computers
even smaller and faster.

Fourth Generation Computers
 In 1970 the Intel Corporation invented the
Microprocessor: an entire CPU on one chip
 This led to microcomputers-computers on a desk

Computer Programming
in the ’70’s
 If you learned computer
programming in the
1970's, you dealt with
what today are called
mainframe computers
 such as the IBM 7090
(shown below), IBM
360, or IBM 370.

Programming Today
 But things changed
fast.
 By the 1990's a
university student
would typically own his
own computer and
have exclusive use of it
in his dorm room.

Microprocessor
 This transformation was a
result of the invention of the
microprocessor.
 A microprocessor (uP) is a
computer that is fabricated
on an integrated circuit (IC).
 Computers had been
around for 20 years before
the first microprocessor was
developed at Intel in 1971.

Microprocessor
 The micro in the name
microprocessor refers
to the physical size.
 Intel didn't invent the
electronic computer,
but they were the first
to succeed in cramming
an entire computer on a
single chip (IC)

Integrated Circuits
 The microelectronics
revolution is what
allowed the amount of
hand-crafted wiring
seen in the prior photo
to be mass-produced
as an integrated
circuit
 It is a small sliver of
silicon the size of your
thumbnail

Integrated Circuits
 Integrated circuits and
microprocessors
allowed computers to
be faster
 This led to a new age
of computers
 The first home-brew
computers is called the
ALTAIR 8800

History of computers

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