world of computers

8/8/2019 World of Computers

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Presented By:-

Varsha. Sukhramani

Shabeen. Samnani


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Introduction

History of Computing

How Where Computers Introduces

Abacus Computers

Charles Babbage

Harvard Mark I

ENIAC Computers

Super Computers

Development of Computers

How Computers Work


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Acomputer is a machine which manipulates data according to a list of

instructions.

The first devices that resemble modern computers date to mid-20th

century(around 1940-1941). Early electronic computers were the size of a large

room, consuming as much power as several hundred modern personal

computers. Today, simple computers may be made small enough to fit into a

wrist watch and be powered from a watch battery. However, the most

common form of computer in use today is by far the embedded computer.

Embedded computers are small, simple devices that are often used to control

other devices.

Any computer with a certain minimum capability is, in principal, capable

of performing the same tasks that any other computer can perform.


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It is difficult to identify any one device as the earliest computer, partly because the

term "computer" has been subject to varying interpretations over time.Originally, the

term "computer" referred to a person who performed numerical calculations (a human

computer), often with the aid of a mechanical calculating device.. In 1801, Joseph

Marie Jacquard made an improvement to the textile loom that used a series of punchedpaper cards as a template to allow his loom to weave intricate patterns automatically.

In 1837, Charles Babbage was the first to conceptualize and design a fully

programmable mechanical computer that he called "TheAnalytical Engine".During the

first half of the 20th century, many scientific computing needs were met by increasingly

sophisticated analog computers, which used a direct mechanical or electrical model of

the problem as a basis for computation. However, these were not programmable and

generally lacked the versatility and accuracy of modern digital computers.Asuccession

of steadily more powerful and flexible computing devices were constructed in the 1930s

and 1940s, gradually adding the key features that are seen in modern computers


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The first to be demonstrated working was the Manchester Small-Scale Experimental Machine

(SSEM) ,while the technologies used in computers have changed dramatically since the first

electronic general-purpose computers of the 1940s.Vacuum tube-based computers were in use

throughout the 1950s, but were largely replaced in the 1960s, which were smaller, faster,

cheaper, used less power and were more reliable. By the 1970s, the adoption of integrated

circuit technology and the subsequent creation of microprocessors such as theIntel 4004 whichwere, speed, cost and reliability. The early and mid-1980s saw machines with a modest number

of vector processors working in parallel become the standard. Typical numbers of processors

were in the range of four to sixteen. By the 1980s, computers had become sufficiently small and

cheap to replace simple mechanical controls in domestic appliances such as washing machines.

Around the same time, computers became widely accessible for personal use by individuals in theform of home computers and the now ubiquitous personal computer. In the later 1980s and

1990s, attention turned from vector processors to massive parallel processing systems with

thousands of "ordinary" CPUs, some being off the shelf units and others being custom designs.

In conjunction with the widespread growth of theInternet since the 1990s, personal computers

are becoming as common as the television and the telephone and almost all modern electronicdevices contain a computer of some kind.


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The modern Abacus

The old Abacus

TheAbacus was an early aid for mathematical computations. Its only value is

that it aids the memory of the human performing the calculations. Askilled

abacus operator can work on addition and subtraction problems at the speedof a person equipped with a hand calculator (multiplication and division are

slower). The oldest survivingAbacus was used in 300bc, by the Babylonians.

TheAbacus is still an use today, principally in far east. AmodernAbacus

consists of rings that slide over rods but the older one dates from the time

when pebbles were used for counting. The modernAbacus is just therepresentation of the human fingers: the lower rings on each rod represent the

5 fingers and the 2 upper rings represent the 2 hands.


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Small section of the type of mechanism employed in Babbage's Difference Engine

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. This machine would be able to compute tables of numbers, such aslogarithm tables. He obtained government funding for this project due to the

importance of numeric tables in ocean navigation.It was Babbage who made an important intellectual leap regarding the punched

cards. Babbage realized that punched paper could be employed as a storage

mechanism, holding computed numbers for future reference. Babbage called thetwo main parts of hisAnalytic 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).


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The Harvard Mark I: an electro-mechanical computer

One early success was the Harvard MarkIcomputer which was built as a partnership

between Harvard andIBM in 1944. This was the first programmable digital computer

made in the U.S. But it was not a purely electronic computer. Instead the MarkIwas

constructed out of switches, relays, rotating shafts, and clutches.

One of the primary programmers for the MarkIwas a woman, Grace Hopper. Hopperfound the first computer "bug. 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.

The MarkIoperated on numbers that were 23 digits wide. It could add or subtract

two of these numbers in three-tenths of a second, multiply them in four seconds, and

divide them in ten seconds. Forty-five years later computers could perform an addition

in a billionth of a second!. This kind of speed is obviously impossible for a machine

which must move a rotating shaft and that is why electronic computers killed off their

mechanical predecessors.


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"Electronic Numerical Integrator and Calculator"

The title of forefather of today's all-electronic digital computers is usually

awarded to ENIAC, which stood for Electronic NumericalIntegrator and

Calculator. ENIAC was built at the University of Pennsylvania between 1943and 1945 by two professors, John Mauchly and the 24 year old J. Presper

Eckert, . Like the MarkI, ENIAC employed paper card readers obtained from

IBM.

To perform this computation on ENIAC you had to rearrange a large number ofpatch cords and then locate three particular knobs on that vast wall of knobs

and set them to 3, 1, and 4.

One of the most obvious problems was that the design would require 18,000

vacuum tubes to all work simultaneously


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The Cray-2 was the world's fastest computer from 1985 to 1989.

Asupercomputer is a computer that is considered, or was considered at the time of

its introduction, to be at the frontline in terms of processing capacity, particularly

speed of calculation.

Supercomputers introduced in the 1960s were designed primarily by Seymour Cray

at Control Data Corporation (CDC), and led the market into the 1970s until Crayleft to form his own company, Cray Research. He then took over the supercomputer

market with his new designs, holding the top spot in supercomputing for five years

(19851990).

The term supercomputer itself is rather fluid, and today's supercomputer tends to

become tomorrow's normal computer. In the 1970s most supercomputers were

dedicated to running a vector processor, Today, parallel designs are based on "off the

shelf" server-class microprocessors, such as the PowerPC, Itanium, or x86-64, and

most modern supercomputers are now highly-tuned computer clusters using

commodity processors combined with custom interconnects.


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As time progressed, people found they were using adding machines and slide rules toperform more and more extremely tedious calculations. Aiken, developed the MarkI

in 1944 to ease this calculating burden. During World WarII, researchers made

more advances to ease the burden of performing calculations. In 1946, they

developed the ENIA

C, Electronic NumericalIntegrator and Calculator. Thecomputer had 18,000 vacuum tubes which were used to perform calculations at a

rate of 5,000 additions per second.. In the next few years, a number of other "first

generation" computers were built. All of these early computers used vacuum tubes to

perform their calculations. In 1945, John von Neumann wrote a paper describing

how a binary program could be electronically stored in a computer .In 1947, theEDVAC, Electronic Discrete VariableAutomatic Computer, was built by Eckert

and Mauchley. In 1951, Eckert and Mauchley built the UNIVAC for use at the

Census Bureau. The UNIVAC used magnetic tape to store input/output rather

than the punch tape. In 1953, IBM continued to develop and expand its computer

line and within the next decade. Digital Equipped Computer


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Vanguard Motion AnalyzrSmall

In 1947, Bell Laboratories invented the transistor. This creation sparked the

production of a wave of "second generation" computers. By using transistors

in place of vacuum tubes, manufacturers could produce more reliable

computers. Using transistors was also less expensive than building acomputer with vacuum tubes. The combination of smaller size, better

reliability, and lower cost made these second generation computers very

popular with buyers. For scientists and engineers, large powerful computers

were built which were good at performing calculations. For banks andinsurance companies, computers which were smaller , faster and those which

were good at sorting and printing were built. Computer companies found

that it was expensive to produce two different lines of computers, so they set

to work to develop a computer which could perform both calculations and

data processing equally well.


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Vectral General Computer

In 1958, the first integrated circuit was made. This invention has led to the

widespread use of computers today. Scientists found a way to reduce the size

of transistors so they could place hundreds of them on a small silicon chip,

about a quarter of an inch on each side. This enabled computermanufacturers to build smaller computers. In 1956, FORTRAN, the first

programming language, was developed. The introduction of programming

languages enabled this third generation of computers to contain something

called an operating system.. Another aspect of new computing to the thirdgeneration machines was the presence of multiprogramming. It enabled the

computer to run a number of jobs simultaneously. The companies whomanufactured the third generation computers tried to create computers which

could successfully perform both calculations and sorts.


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Then, in 1971 Intel created the first microprocessor. The microprocessor was a

large-scale integrated circuit which contained thousands of transistors. In 1976,

Steve Jobs and Steve Wozniak built the firstApple computer in a garage in

California. Then, in 1981,IBM introduced its first personal computer. Thepersonal computer was such a revolutionary concept and was expected to have

such an impact on society that in 1982. Within a matter of years, computers

spread from the work place into the home. Personal computers have changed a

great deal since the early eighties. The hardware has definitely changed, the

computers are faster now, have more memory, The increased processing speed andmemory in computers has led to an increase in the quality of computer graphics.

The introduction of the integrated circuit and its development into the very-large

scale integrated circuit started a technological revolution which caused computers

to invade almost every aspect of our society.


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Control Unit

Memory

Input/output (I/O)

Arithmetic/Logic Unit (ALU)


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The control unit directs the various components of a computer. It reads and interprets

instructions in the program. Control systems in advanced computers may change theorder of some instructions so as to improve performance. Akey component common to

all CPUs is the program counter. The control system's function is as follows. Some of

these steps may be performed concurrently or in a different order depending on the type

of CPU:-

Read the code for the next instruction from the cell indicated by the program counter.Decode the numerical code for the instruction into a set of commands or signals for

each of the other systems.

Increment the program counter so it points to the next instruction.

Read whatever data the instruction requires from cells in memory. The location of

this required data is typically stored within the instruction code.Provide the necessary data to anALU or register.

If the instruction requires anALU or specialized hardware to complete, instruct the

hardware to perform the requested operation.

Write the result from theALU back to a memory location or to a register or perhaps

an output device.


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Magnetic Core Memory

Magnetic core memory was popular main memory for computers through the 1960suntil it was completely replaced by semiconductor memory.

Acomputer's memory can be viewed as a list of cells into which numbers can be placed

or read. The information stored in memory may represent practically anything. Letters,

numbers, even computer instructions. In almost all modern computers, each memory cell

is set up to store binary numbers in groups of eight bits (called a byte). Each byte is ableto represent 256 different numbers. Acomputer can store any kind of information in

memory as long as it can be somehow represented in numerical form. Computer main

memory comes in two principal varieties: random access memory or RAM and read-only

memory or ROM. ROM is pre-loaded with data and software that never changes. The

contents of RAM is erased when the power to the computer is turned off while ROM

retains its data indefinitely Software that is stored in ROM is often called firmware

because it is notionally more like hardware than software. Flash memory blurs the

distinction between ROM and RAM by retaining data when turned off but being

rewritable like RA

M.In more sophisticated computers there may be one or more R

AMcache memories which are slower than registers but faster than main memory.


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Common I/O Devices Used With Computers

Hard disks are CommonI/O devices used with computers.I/O is the means by

which a computer receives information from the outside world and sends results

back. Devices that provide input or output to the computer are called

peripherals. On a typical personal computer, peripherals include input deviceslike the keyboard and mouse, and output devices such as the display and printer.

Hard disk drives, floppy disk drives and optical disc drives serve as both input

and output devices. Computer networking is another form ofI/O.Often, I/O

devices are complex computers in their own right with their own CPU andmemory. Agraphics processing unit might contain fifty or more tiny computers

that perform the calculations necessary to display 3D graphics. Modern desktop

computers contain many smaller computers that assist the main CPU in

performingI/O.


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TheALU is capable of performing two classes of operations: arithmetic and

logic.The set of arithmetic operations that a particularALU supports may be

limited to adding and subtracting or might include multiplying or dividing.A

nycomputer can be programmed to perform any arithmetic operationalthough it

will take more time to do so if itsALU does not directly support the operation..

Logic operations involve Boolean logic: AND, OR, XOR and NOT. These can be

useful both for creating complicated conditional statements and processing

boolean logic.Superscalar computers contain multipleALUs so that they canprocess several instructions at the same time. Graphics processors and computers

with SIMD and MIMD features often provideALUs that can perform

arithmetic on vectors and matrices.


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