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This is an IBM System/360.
Acomputer is amachine that useselectronics to input, process, store, and outputdata. Data is information such as numbers, words, and lists. Input of data means to read information from a keyboard, a storage device like ahard drive, or asensor. The computer processes or changes the data by following the instructions insoftware programs. A computer program is a list of instructions the computer has to perform. Programs usually perform mathematical calculations, modify data, or move it around. The data is then saved on a storage device, shown on adisplay, or sent to another computer. Computers can be connected together to form anetwork such as theinternet, allowing the computers to communicate with each other.
Theprocessor of a computer is made fromintegrated circuits (chips) that contains manytransistors. Most computers aredigital, which means that they represent information usingbinarydigits, orbits. Computers come in different shapes and sizes, depending on the brand, model, and purpose. They range from small computers, such as smartphones andlaptops, to large computers, such assupercomputers.
Two things that often define a computer are that it responds to a specificinstruction set in a well-defined manner, and that it can execute a stored list of instructions called aprogram. There are four main actions in a computer:inputting,storing,outputting and processing.
Modern computers can do billions of calculations in a second. Being able to calculate many times per second allows modern computers to multi-task, which means they can do many different tasks at the same time. Computers do many different jobs whereautomation is useful. Some examples are controllingtraffic lights, vehicles, security systems,washing machines and digital televisions.
Computers can be designed to do almost anything with certain information. Computers are used to control large and small machines that, in the past, were controlled by humans. Billions of people have apersonal computer at home or at work. They are used for things such as calculation, listening to music, reading, writing, or playinggames.
Modern computers are electroniccomputer hardware. They do mathematicalarithmetic very quickly, but computers do not really "think." They only follow the instructions in their software programs. Thesoftware uses the hardware when the user gives it instructions and produces useful outputs.
Computer programs are designed or written bycomputer programmers. A few programmers write programs in the computer's own language, calledmachine code. Most programs are written using aprogramming language like:C,Fortran,JavaScript,Lisp, andPascal. These programming languages are more like the language with which one talks and writes every day. Thecompiler converts the user's instructions into binary code (machine code) that the computer will understand and do what is needed.
In 1837,Charles Babbage proposed the first general mechanical computer, the Analytical Engine. The Analytical Engine contained an ArithmeticLogic Unit, basic flow control,punched cards, and integrated memory. It is the first general-purpose computer concept that could be used for many things and not only one particular program. However, this computer was never built while Charles Babbage was alive, because he didn't have enough money. In 1910, Henry Babbage, Charles Babbage's youngest son, was able to finish a part of this machine and do basic calculations.
Before the computer era there were machines that could do the same thing over and over again, like a music box. People began to want to be able to tell their machine to do different things. For example, they wanted to tell the music box to play different music every time. This part of computer history is called the "history of programmable machines", which in simple words means "the history of machines that I can order to do different things if I know how to speak their language."
One of the first examples of programmable machines was built byHero of Alexandria (c. 10–70AD). He built a mechanical theater which performed a play lasting 10minutes 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 people argue that this is the first programmable machine.[1]
Some people disagree on which early computer is programmable. Many say the "castle clock", anastronomical clock invented byAl-Jazari in 1206, is the first knownprogrammableanalog computer.[2][3] The length ofday andnight could be adjusted every day in order to account for the changing lengths of day and night throughout the year.[4] Some count this daily adjustment as computer programming.
At the end of theMiddle Ages, people started thinking math andengineering were more important. In 1623, Wilhelm Schickard made a mechanicalcalculator. Other Europeans made more calculators after him. They were not modern computers because they could only add, subtract, and multiply- you could not change what they did to make them do something like playTetris. Because of this, we say they were not programmable. Now engineers use computers to design and plan.
In 1801,Joseph Marie Jacquard usedpunched paper cards to tell histextile loom what kind of pattern to weave. He could use punch cards to tell the loom what to do, and he could change the punch cards, which means he could program the loom to weave the pattern he wanted. This means the loom was programmable. At the end of the 1800s Herman Hollerith invented the recording of data on a medium that could then be read by a machine, developing punched card data processingtechnology for the 1890 U.S. census. His tabulating machines read and summarized data stored on punched cards and they began use for government and commercial data processing.
Charles Babbage wanted to make a similar machine that could calculate. He called it "The Analytical Engine".[8] Because Babbage did not have enough money and always changed his design when he had a better idea, he never built his Analytical Engine.
As time went on, computers were used more. People get bored easily doing the same thing over and over. Imagine spending your life writing things down on index cards, storing them, and then having to go find them again. TheU.S. Census Bureau in 1890 had hundreds of people doing just that. It was expensive, and reports took a long time. Then an engineer worked out how to make machines do a lot of the work.Herman Hollerith invented a tabulating machine that would automatically add up information that the Census bureau collected. The Computing Tabulating Recording Corporation (which later becameIBM) made his machines. Theyleased the machines instead of selling them. Makers of machines had long helped their users understand and repair them, and CTR's tech support was especially good.
Because of machines like this, new ways of talking to these machines were invented, and new types of machines were invented, and eventually the computer as we know it was born.
In the first half of the20th century,scientists started using computers, mostly because scientists had a lot of math to figure out and wanted to spend more of their time thinking about science questions instead of spending hours adding numbers together. For example, if they had to launch arocket ship, they needed to do a lot of math to make sure the rocket worked right. So they put together computers. Theseanalog computers usedanalog circuits, which made them very hard to program. In the1930s, they inventeddigital computers, and soon made them easier to program. However this is not the case as many consecutive attempts have been made to bring arithmetic logic to l3.Analog computers are mechanical or electronic devices which solve problems.Some are used to control machines as well.
Scientists figured out how to make and use digital computers in the1930s to1940s. Scientists made a lot of digital computers, and as they did, they figured out how to ask them the right sorts of questions to get the most out of them. Here are a few of the computers they built:
EDSAC was one of the first computers that remembered what you told it even after you turned the power off. This is called (von Neumann) architecture.
Konrad Zuse'selectromechanical "Z machines". TheZ3 (1941) was the first working machine that usedbinary arithmetic. Binary arithmetic means using "Yes" and "No." to add numbers together. You could also program it. In1998 the Z3 was proved to beTuring complete. Turing complete means that it is possible to tell this particular computer anything that it is mathematically possible to tell a computer. It is the world's first modern computer.
TheHarvard Mark I (1944), A big computer that you could kind of program.
The U.S. Army's Ballistics Research LaboratoryENIAC (1946), which could add numbers the way people do (using the numbers 0 through 9) and is sometimes called the first general purposeelectronic computer (sinceKonrad Zuse'sZ3 of 1941 usedelectromagnets instead ofelectronics). At first, however, the only way to reprogram ENIAC was by rewiring it.
Several developers of ENIAC saw its problems. They invented a way to for a computer to remember what they had told it, and a way to change what it remembered. This is known as "stored program architecture" orvon Neumann architecture.John von Neumann talked about this design in the paperFirst Draft of a Report on theEDVAC, distributed in 1945. A number of projects to develop computers based on the stored-program architecture started around this time. The first of these was completed inGreat Britain. The first to be demonstrated working was theManchester Small-Scale Experimental Machine (SSEM or "Baby"), while theEDSAC, completed a year after SSEM, was the first really useful computer that used the stored program design. Shortly afterwards, the machine originally described by von Neumann's paper—EDVAC—was completed but was not ready for two years.
Nearly all modern computers use the stored-program architecture. It has become the mainconcept which defines a modern computer. 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 programCPUs.
In the 1950s computers were built out of mostlyvacuum tubes.Transistors replaced vacuum tubes in the 1960s because they were smaller and cheaper. They also need less power and do not break down as much as vacuum tubes. In the 1970s, technologies were based onintegrated circuits.Microprocessors, such as theIntel 4004 made computers smaller, cheaper, faster and more reliable. By the 1980s,microcontrollers became small and cheap enough to replace mechanical controls in things likewashing machines. The 1980s also sawhome computers andpersonal computers. With the evolution of theInternet, personal computers are becoming as common as thetelevision and thetelephone in the household.
In 2005 Nokia started to call some of its mobile phones (the N-series) "multimedia computers" and after the launch of the AppleiPhone in 2007, many are now starting to add thesmartphone category among "real" computers. In 2008, if smartphones are included in the numbers of computers in the world, the biggest computer maker by units sold, was no longer Hewlett-Packard, but ratherNokia.[9]
A "desktop computer" is a small machine that has a screen (which is not part of the computer). Most people keep them on top of a desk, which is why they are called "desktop computers." "Laptop computers" are computers small enough to fit on your lap. This makes them easy to carry around. Both laptops and desktops are called personal computers, because one person at a time uses them for things like playing music, surfing the web, or playing video games.
There are larger computers that can be used by multiple people at the same time. These are called "mainframes," and these computers do all the things that make things like the internet work. You can think of a personal computer like this: the personal computer is like your skin: you can see it, other people can see it, and through your skin you feel wind, water, air, and the rest of the world. A mainframe is more like your internal organs: you never see them, and you barely even think about them, but if they suddenly went missing, you would have some very big problems.
An embedded computer, also called anembedded system is a computer that does one thing and one thing only, and usually does it very well. For example, analarm clock is an embedded computer. It tells the time. Unlike your personal computer, you cannot use your clock to play Tetris. Because of this, we say that embedded computers cannot be programmed because you cannot install more programs on your clock. Somemobile phones,automatic teller machines,microwave ovens,CD players andcars are operated by embedded computers.
All-in-one computers aredesktop computers that have all of the computer's inner mechanisms in the same case as themonitor.Apple has made several popular examples of all-in-one computers, such as theoriginal Macintosh of the mid-1980s and theiMac of the late 1990s and 2000s.
Computers store data and the instructions as numbers, because computers can do things with numbers very quickly. These data are stored asbinarysymbols (1s and 0s). A 1 or a 0 symbol stored by a computer is called abit, which comes from the words binarydigit. Computers can use many bits together to representinstructions and the data that these instructions use. A list of instructions is called aprogram and is stored on the computer'shard disk. Computers work through the program by using acentral processing unit, and they use fast memory calledRAM (also known as Random Access Memory) as a space to store the instructions and data while they are doing this. When the computer wants to store the results of the program for later, it uses thehard disk because things stored on a hard disk can still be remembered after the computer is turned off.
Anoperating system tells the computer how to understand what jobs it has to do, how to do these jobs, and how to tell people the results. Millions of computers may be using the sameoperating system, while each computer can have its ownapplication programs to do what its user needs. Using the sameoperating systems makes it easy to learn how to use computers for new things. A user who needs to use a computer for something different, can learn how to use a new application program. Someoperating systems can have simple command lines or a fully user-friendlyGUI.
One of the most important jobs that computers do for people is helping withcommunication. Communication is how people shareinformation. Computers have helped people move forward inscience,medicine,business, andlearning, because they let experts from anywhere in the world work with each other and share information. They also let other people communicate with each other, do their jobs almost anywhere, learn about almost anything, or share their opinions with each other. TheInternet is the thing that lets people communicate between their computers. The Internet also allows the computer user to play anOnline game.
A computer is now almost always anelectronic device. It usually contains materials that will becomeelectronic waste when discarded. When a new computer is bought in some places, laws require that the cost of itswaste management must also be paid for. This is calledproduct stewardship.
Computers can becomeobsolete quickly, depending on what programs the user runs. Very often, they are thrown away within two or three years, because some newer programs require a more powerful computer. This makes the problem worse, socomputer recycling happens a lot. Many projects try to send working computers todeveloping nations so they can be re-used and will not become waste as quickly, as most people do not need to run new programs. Some computer parts, such ashard drives, can break easily. When these parts end up in thelandfill, they can putpoisonous chemicals likelead into the ground-water. Hard drives can also contain secret information likecredit card numbers. If the hard drive is not erased before being thrown away, anidentity thief can get the information from the hard drive, even if the drive doesn't work, and use it, for example, to steal money from the previous owner's bank account.
All computers have some kind ofdata bus which 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 hold information.
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 otherperipheral devices connected.
A computer has several main parts. When comparing a computer to ahuman body, theCPU is like a brain. It does most of the thinking and tells the rest of the computer how to work. The CPU is on theMotherboard, which is like the skeleton. It provides the basis for where the other parts go, and carries thenerves that connect them to each other and the CPU. The motherboard is connected to a power supply, which provideselectricity to the entire computer. The various drives (CD drive,floppy drive, and on many newer computers,USB flash drive) act like eyes, ears, and fingers, and allow the computer to read different types of storage, in the same way that a human can read different types of books. Thehard drive is like a human's memory, and keeps track of all the data stored on the computer. Most computers have asound card or another method of making sound, which is likevocal 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 create visual effects, such as3D 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.
↑Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East",Scientific American, May 1991, pp. 64-9 (compare Donald Routledge Hill,Mechanical EngineeringArchived 2007-12-25 at theWayback Machine)
↑Phillips, Ana Lena (November–December 2011). "Crowdsourcing gender equity: Ada lovelace day, and its companion website, aims to raise the profile of women in science and technology".American Scientist.99 (6): 463.doi:10.1511/2011.93.463.ISSN0003-0996.
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