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The abacus, the slide ruleand arguably the astrolabe and theAntikythera mechanism (which dates from about

150-100 BC) are examples of automated calculation machines.

Some people did not want a machine that would do the same thing over and over again. For example, a musicbox is a machine that plays the same music over and over again. Some people wanted to be able to tell their

machine to do different things. For example, they wanted to tell the music box to play different music everytime. They wanted to be able to program the music box- to order the music box to play different music. This

part of computer history is called the "history of programmable machines" which is a fancy phrase for "Thehistory of machines that I can order to do different things if I know how to speak their language."

One of the first examples of this was built by Hero of Alexandria (c. 1070 AD). He built a mechanical theate

which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums. These

ropes and drums were the language of the machine- they told what the machine did and when. Some peopleargue that this is the first programmable machine.[1]

Most historians agree that the "castle clock", anastronomical clockinvented byAl-Jazari in 1206, is first know

programmableanalog computer.

[2]

It showed the zodiac, the solarand lunar orbits, a crescent moon-shapedpointertravelling across a gateway causing automatic doors to open every hour,[3][4] and five robotic musicians

who play music when struck by levers operated by acamshaft attached to awater wheel. The length ofday an

night could be re-programmed every day in order to account for the changing lengths of day and night

throughout the year.[2]

At the end of the Middle Ages, people in Europe though math andengineeringwere more important. In 1623,

Wilhelm Schickard made a mechanical calculator. Other Europeans made more calculators after him. They

were not modern computers because they could not be programmed.

In 1801, Joseph Marie Jacquard usedpunched paper cards to tell his textile loom how to weave complicated

patterns. The Jacquard loom's use of punched cards to define woven patterns is an early form ofprogrammability.

Modern computers were made when someone (Charles Babbage) had a bright idea. He wanted to make a

machine that could do all the boring parts of math, (like the automated calculators) and could be told to do thedifferent ways (like the programmable machines.) Charles Babbage was the first to make a design of a fully

programmable mechanical computer. He called it the "TheAnalytical Engine".[5] Because Babbage did not hav

enough money and always changed his design when he had a better idea, he never built his Analytical Engine.

Large-scale automatic data processing of punched cards was performed for the U.S. Census in 1890bytabulating machinesdesigned by Herman Hollerith and manufactured by the Computing Tabulating Recording

Corporation, which later became IBM. By the end of the 19th century a number of technologies that would latprove useful in the realization of practical computers had begun to appear: thepunched card, Boolean algebra,the vacuum tube(thermionic valve) and the teleprinter.

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

sophisticated analog computers, which used a direct mechanical orelectrical model of the problem as a basis f

computation. However, these were not programmable and generally lacked the versatility and accuracy ofmodern digital computers.
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Computing devices became more powerful and flexible during the 1930s and 1940s. The features that are seen

as defining a modern-day computer were added during this time. The use of digital electronics (largely invente

by Claude Shannon in 1937) and more flexible programmability were very important steps. It is difficult todefine one point along this road as "the first digital electronic computer"(Shannon 1940). Notable achievemen

include:

EDSAC was one of the first computers to implement the stored program (von Neumann) architecture.

Konrad Zuse's electromechanical "Z machines". TheZ3 (1941) was the first working machine featurin

binary arithmetic, including floating point arithmetic and a measure of programmability. In 1998 the Z

was proved to be Turing complete, therefore being the world's first operational computer.

The non-programmable AtanasoffBerry Computer(1941) which used vacuum tube basedcomputatiobinary numbers, and regenerative capacitor memory.

The secret British Colossus computers (1943)[6], which had limited programmability but demonstrated

that a device using thousands of tubes could be reasonably reliable and electronically reprogrammableIt was used forbreaking German wartime codes.

The Harvard Mark I (1944), a large-scale electromechanical computer with limited programmability.

The U.S. Army's Ballistics Research LaboratoryENIAC (1946), which used decimal arithmetic and issometimes called the first general purpose electronic computer (sinceKonrad Zuse's Z3 of 1941 used

electromagnets instead ofelectronics). Initially, however, ENIAC had an inflexible architecture which

essentially required rewiring to change its programming.

Several developers of ENIAC saw its problems. They invented a more flexible and elegant design, which isknown as "stored program architecture" orvon Neumann architecture. This design was first formally describe

by John von Neumannin the paperFirst Draft of a Report on the EDVAC, distributed in 1945. A number of

projects to develop computers based on the stored-program architecture started around this time, the first ofthese was completed inGreat Britain. The first to be demonstrated working was the Manchester Small-Scale

Experimental Machine (SSEM or "Baby"), while the EDSAC, completed a year after SSEM, was the first

practical implementation of the stored program design. Shortly thereafter, the machine originally described by

von Neumann's paperEDVACwas completed but did not see full-time use for an additional two years.
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.wikipedia.org/wiki/John_von_Neumannhttp://simple.wikipedia.org/w/index.php?title=First_Draft_of_a_Report_on_the_EDVAC&action=edit&redlink=1http://simple.wikipedia.org/wiki/Great_Britainhttp://simple.wikipedia.org/w/index.php?title=Manchester_Small-Scale_Experimental_Machine&action=edit&redlink=1http://simple.wikipedia.org/w/index.php?title=Manchester_Small-Scale_Experimental_Machine&action=edit&redlink=1http://simple.wikipedia.org/w/index.php?title=EDSAC&action=edit&redlink=1http://simple.wikipedia.org/w/index.php?title=EDVAC&action=edit&redlink=1


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Nearly all modern computers implement the stored-program architecture in some form. It has become the main

conceptwhich defines a modern computer. Most of the technologies used to build computers have changed

since the 1940s, but many current computers still use the von-Neumann architecture.

Microprocessors are miniaturized devices that often implement stored program CPUs.

Computers that used vacuum tubes as their electronic elements were in use throughout the 1950s. Vacuum tubelectronics were largely replaced in the 1960s by transistor-based electronics, which are smaller, faster and

cheaper to produce. They also need less power and are more reliable than vacuum tubes. In the 1970s,

technologies were based on integrated circuits.Microprocessors, such as the Intel 4004, further decreased sizeand cost. They also made computers faster and more reliable. By the 1980s, computers became small and chea

enough to replace simple mechanical controls in domestic appliances such as washing machines. The 1980s al

saw home computersand the now ubiquitouspersonal computer. With the evolution of the Internet, personal

computers are becoming as common as thetelevisionand the telephone in the household.

In 2005 Nokia started to call its top-line smartphones of the N-series "multimedia computers" and after the

launch of the Apple iPhonein 2007, many are now starting to add the smartphone category among "real"

computers. In 2008, if the category of smartphones are included in the numbers of computers in the world, thebiggest computer maker by units sold, is no longer Hewlett-Packard, but rather Nokia.[needsproving]

[change] Kinds of computers

A "desktop computer" is a small machine which is usually accompanied by a screen (which is not part of the

computer) and used at a household. "Laptop computers" are portable computers that are commonly used forwork or personal media purposes. Both laptops and desktops are considered personal computers. "Mainframes

are large computers used for managing businesses or hosting servers. "Embedded computers" are computer

systems that cannot be programmed by the user because they are preprogrammed for a specific task and are

buried within the equipment they serve. For example, in mobile phones,automatic teller machines, microwaveovens, CD playersand cars.

[change] How computers work

Computers store data and the instructions telling them what to do with the data as numbers, because computer

can do things with numbers very quickly. These data are stored asbinarysymbols(1s and 0s). A 1 or a 0symbol stored by a computer is called abit, which comes from the words binary digit. Computers can use man

bits together to represent instructions and the data that these instructions use. A list of these instructions is

called aprogram and stored on the computer's hard disk. Computers use memory called "RAM" as a space to
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carry out the instructions and store data while it is doing these instructions. When the computer wants to store

the results of the instructions for later, it uses the hard disk.

An operating systemtells the computer how to understand what jobs it has to do, how to do these jobs, and hoto tell people the results. It tells the electronics inside the computer, or "hardware", how to work to get the

results it needs. This lets most computers have the sameoperating system, or list of orders to tell it how to talkto the user, while each computer can have its own computer programs or list of jobs to do what its user needs.

Having different programs and operating systems makes it easy to learn how to use computers for new things.When a user needs to use a computer for something different, the user can learn how to use a new program.

[change] Computers and the Internet

One of the most important jobs that computers do for people is helping with communication. Communication

how people share information. Computers have helped people move forward in science,medicine,business, anlearning, because they let experts from anywhere in the world work with each other and share information.

They also let otherpeople communicate with each other, do their jobs almost anywhere, learn about almost

anything, or share their opinions with each other. The Internet is the thing that letspeople communicatebetween their computers.

[change] The main hardware in a computer

Computers come in different forms, but most of them have a common architecture.

All computers have a CPU

All computers have some kind ofdata buswhich lets them get inputs or output things to the

environment.

All computers have some form of memory. These are usually chips (integrated circuits) which can holdinformation. Many computers have some kind of sensors, which lets them get input from their environment.

Many computers have some kind of display device, which lets them show output. They may also have

other peripheral devices connected.

A computer has several main parts. When comparing a computer to a human body, the CPUis like a brain. Itdoes most of the 'thinking' and tells the rest of the computer how to work. The CPU is on the Motherboard,

which is like the skeleton. It provides the basis for where the other parts go, and carries the nerves that connec

them to each other and the CPU. The motherboard is connected to a power supply, which provides electricity tthe entire computer. The various drives (CDdrive, floppy drive, and on many newer computers, USB drive) a

like eyes, ears, and fingers, and allow the computer to read different types of storage, in the same way that ahuman can read different types of books. The hard drive is like a human's memory, and keeps track of all thedata stored on the computer. Most computers have a sound cardor another method of making sound, which is

like vocal cords, or a voice box. Connected to the sound card arespeakers, which are like a mouth, and are

where the sound comes out. Computers might also have agraphics card, which helps the computer to createvisual effects, such as 3D environments, or more realistic colors, and more powerful graphics cards can make

more realistic or more advanced images, in the same way a well trained artist can.
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a computer is a machine that changes information when it

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