HISTORY OF COMPUTER

           
       History Of Computing

A computer might be described with deceptive
simplicity as “an apparatus that performs routine
calculations automatically.” Such a definition would
owe its deceptiveness to a naive and narrow view
of calculation as a strictly mathematical process. In
fact, calculation underlies many activities that are
not normally thought of as mathematical. Walking
across a room, for instance, requires many
complex, albeit subconscious, calculations.
Computers, too, have proved capable of solving a
vast array of problems, from balancing a checkbook
to even—in the form of guidance systems for robots
—walking across a room.
FRI 20:00 LIVERPOOL TO WIN 1.15
SAT12:30 WEST HAM TO WIN 10.7
SAT15:00 B'MOUTH TO WIN 1.98
SAT15:00 BURNLEY TO WIN 2.67
SAT15:00 C PALACE TO WIN 3.05
YOUR 100₦
ACCA PAYS 115₦
BET NOW
Before the true power of computing could be
realized, therefore, the naive view of calculation had
to be overcome. The inventors who laboured to
bring the computer into the world had to learn that
the thing they were inventing was not just a number
cruncher, not merely a calculator. For example, they
had to learn that it was not necessary to invent a
new computer for every new calculation and that a
computer could be designed to solve numerous
problems, even problems not yet imagined when
the computer was built. They also had to learn how
to tell such a general problem-solving computer
what problem to solve. In other words, they had to
invent programming.
They had to solv

 the heady problems of
developing such a device, of implementing the
design, of actually building the thing. The history of
the solving of these problems is the history of the
computer. That history is covered in this section,
and links are provided to entries on many of the
individuals and companies mentioned. In addition,
see the articles computer science and
supercomputer.
Early history
Computer precursors
The abacus
The earliest known calculating device is probably
the abacus . It dates back at least to 1100 BCE and
is still in use today, particularly in Asia. Now, as
then, it typically consists of a rectangular frame with
thin parallel rods strung with beads. Long before
any systematic positional notation was adopted for
the writing of numbers, the abacus assigned
different units, or weights, to each rod. This scheme
allowed a wide range of numbers to be represented
by just a few beads and, together with the invention
of zero in India, may have inspired the invention of
the Hindu-Arabic number system. In any case,
abacus beads can be readily manipulated to
perform the common arithmetical operations—
addition, subtraction, multiplication, and division—
that are useful for commercial transactions and in
bookkeeping.
The abacus is a digital device; that is, it represents
values discretely. A bead is either in one predefined
position or another, representing unambiguously,
say, one or zero.

Analog calculators: from Napier’s logarithms to the
slide rule
Calculating devices took a different turn when John
Napier, a Scottish mathematician, published his
discovery of logarithms in 1614. As any person can
attest, adding two 10-digit numbers is much
simpler than multiplying them together, and the
transformation of a multiplication problem into an
addition problem is exactly what logarithms enable.
This simplification is possible because of the
following logarithmic property: the logarithm of the
product of two numbers is equal to the sum of the
logarithms of the numbers. By 1624, tables with 14
significant digits were available for the logarithms of
numbers from 1 to 20,000, and scientists quickly
adopted the new labour-saving tool for tedious
astronomical calculations.
Most significant for the development of computing,
the transformation of multiplication into addition
greatly simplified the possibility of mechanization.
Analog calculating devices based on Napier’s
logarithms—representing digital values with
analogous physical lengths—soon appeared. In
1620 Edmund Gunter , the English mathematician
who coined the terms cosine and cotangent, built a
device for performing navigational calculations: the
Gunter scale, or, as navigators simply called it, the
gunter. About 1632 an English clergyman and
mathematician named William Oughtred built the
first slide rule , drawing on Napier’s ideas. That first
slide rule was circular, but Oughtred also built the
first rectangular one in 1633. The analog devices of
Gunter and Oughtred had various advantages and
disadvantages compared with digital devices such
as the abacus. What is important is that the
consequences of these design decisions were being
tested in the real world.




Digital calculators: from the Calculating Clock to
the Arithmometer
In 1623 the German astronomer and mathematician
Wilhelm Schickard built the first calculator . He
described it in a letter to his friend the astronomer
Johannes Kepler, and in 1624 he wrote again to
explain that a machine he had commissioned to be
built for Kepler was, apparently along with the
prototype, destroyed in a fire. He called it a
Calculating Clock, which modern engineers have
been able to reproduce from details in his letters.
Even general knowledge of the clock had been
temporarily lost when Schickard and his entire
family perished during the Thirty Years’ War.
The Calculating ClockA reproduction of Wilhelm
Schickard's Calculating Clock. The device could add
and subtract six-digit numbers (with a bell for
seven-digit overflows) through six interlocking
gears, each of which turned one-tenth of a rotation
for each full rotation of the gear to its right. Thus,
10 rotations of any gear would produce a “carry” of
one digit on the following gear and change the
corresponding display.
The Computer Museum of America
But Schickard may not have been the true inventor
of the calculator. A century earlier, Leonardo da
Vinci sketched plans for a calculator that were
sufficiently complete and correct for modern
engineers to build a calculator on their basis.
The first calculator or adding machine to be
produced in any quantity and actually used was the
Pascaline, or Arithmetic Machine, designed and
built by the French mathematician-philosopher
Blaise Pascal between 1642 and 1644. It could only
do addition and subtraction, with numbers being
entered by manipulating its dials. Pascal invented
the machine for his father, a tax collector, so it was
the first business machine too (if one does not
count the abacus). He built 50 of them over the
next 10 years.

The Arithmetic MachineThe Arithmetic Machine, or
Pascaline, a French monetary (nondecimal)
calculator designed by Blaise Pascal c. 1642.
Numbers could be added by turning the wheels
(located along the bottom of the machine)
clockwise and subtracted by turning the wheels
counterclockwise. Each digit in the answer was
displayed in a separate window, visible at the top
of the photograph.
Courtesy of the Computer Museum History Center
In 1671 the German mathematician-philosopher
Gottfried Wilhelm von Leibniz designed a
calculating machine called the Step Reckoner . (It
was first built in 1673.) The Step Reckoner
expanded on Pascal’s ideas and did multiplication
by repeated addition and shifting.
The Step ReckonerA reproduction of Gottfried
Wilhelm von Leibniz's Step Reckoner, from the
original located in the Trinks Brunsviga Museum at
Hannover, Germany. Turning the crank (left) rotated
several drums, each of which turned a gear
connected to a digital counter.
IBM Archives
Leibniz was a strong advocate of the binary number
system. Binary numbers are ideal for machines
because they require only two digits, which can
easily be represented by the on and off states of a
switch. When computers became electronic, the
binary system was particularly appropriate because
an electrical circuit is either on or off. This meant
that on could represent true, off could represent
false, and the flow of current would directly
represent the flow of logic.
Leibniz was prescient in seeing the appropriateness
of the binary system in calculating machines, but
his machine did not use it. Instead, the Step
Reckoner represented numbers in decimal form, as
positions on 10-position dials. Even decimal
representation was not a given: in 1668 Samuel
Morland invented an adding machine specialized for
British money—a decidedly nondecimal system.