INTRODUCTION Acomputeris a general-purpose device that can beprogrammedto carry out a set ofarithmeticorlogicaloperations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.Conventionally, a computer consists of at least one processing element, typically acentral processing unit(CPU), and some form ofmemory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.Mechanicalanalog computersstarted appearing in the first century and were later used in the medieval era for astronomical calculations. InWorld War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming. During this time the first electronicdigitalcomputers were developed. Originally they were the size of a large room, consuming as much power as several hundred modernpersonal computers(PCs).[1]Modern computers based onintegrated circuitsare millions to billions of times more capable than the early machines, and occupy a fraction of the space.[2]Computers are small enough to fit intomobile devices, andmobile computerscan be powered by smallbatteries. Personal computers in their various forms areiconsof theInformation Ageand are what most people consider as computers. However, theembedded computersfound in many devices fromMP3 playerstofighter aircraftand from electronic toys toindustrial robotsare the most numerous.
BIRTH OF A COMPUTERBefore the 1920s,computers(sometimescomputors) were human clerks that performed computations. They were usually under the lead of a physicist. Many thousands of computers were employed in commerce, government, and research establishments. Most of these computers were women.[citation needed]Some performed astronomical calculations for calendars, others ballistic tables for the military.After the 1920s, the expressioncomputing machinereferred to any machine that performed the work of a human computer, especially those in accordance with effective methods of theChurch-Turing thesis. The thesis states that a mathematical method is effective if it could be set out as a list of instructions able to be followed by a human clerk with paper and pencil, for as long as necessary, and without ingenuity or insight .[citation needed]Machines that computed with continuous values became known as theanalogkind. They used machinery that represented continuous numeric quantities, like the angle of a shaft rotation or difference in electrical potential .[citation needed]Digital machinery, in contrast to analog, were able to render a state of a numeric value and store each individual digit. Digital machinery used difference engines or relays before the invention of faster memory devices .[citation needed]The phrasecomputing machinegradually gave away, after the late 1940s, to justcomputeras the onset of electronic digital machinery became common. These computers were able to perform the calculations that were performed by the previous human clerks .[citation needed]Since the values stored by digital machines were not bound to physical properties like analog devices, a logical computer, based on digital equipment, was able to do anything that could be described "purely mechanical." The theoreticalTuring Machine, created byAlan Turing, is a hypothetical device theorized in order to study the properties of such hardware.[citation needed] HISTORY OF COMPUTERThehistory of computer sciencebegan long before the modern discipline ofcomputer sciencethat emerged in the 20th century, and was hinted at in the centuries prior.[dubiousdiscuss][citation needed]The progression, from mechanical inventions andmathematicaltheories towardsmodern computer concepts and machines, led to a major academic field and the basis of a massive worldwide industry.[1]The earliest known tool for use in computation was theabacus, developed in the period between 27002300 BCE inSumer. The Sumerians' abacus consisted of a table of successive columns which delimited the successive orders of magnitude of theirsexagesimalnumber system.[2]:11Its original style of usage was by lines drawn in sand with pebbles .[citation needed]Abaci of a more modern design are still used as calculation tools today.[3]TheAntikythera mechanismis believed to be the earliest known mechanical analog computer.[4]It was designed to calculate astronomical positions. It was discovered in 1901 in theAntikytherawreck off theGreekisland of Antikythera, between Kythera and Crete, and has been dated to c. 100 BCE. Technological artifacts of similar complexity did not reappear until the 14th century, when mechanicalastronomical clocksappeared inEurope.[5]WhenJohn Napierdiscovered logarithms for computational purposes in the early 17th century,[citation needed]there followed a period of considerable progress by inventors and scientists in making calculating tools. In 1623Wilhelm Schickarddesigned a calculating machine, but abandoned the project, when the prototype he had started building was destroyed by a fire in 1624 .[citation needed]Around 1640,Blaise Pascal, a leading French mathematician, constructed a mechanical adding device based on a design described byGreekmathematicianHero of Alexandria.[6]Then in 1672Gottfried Wilhelm Leibnitzinvented theStepped Reckonerwhich he completed in 1694.[7]In 1837Charles Babbagefirst described hisAnalytical Enginewhich is accepted as the first design for a modern computer. The analytical engine had expandable memory, an arithmetic unit, and logic processing capabilities able to interpret a programming language with loops and conditional branching. Although never built, the design has been studied extensively and is understood to beTuring equivalent. The analytical engine would have had a memory capacity of less than 1 kilobyte of memory and a clock speed of less than 10 Hertz .[citation needed]Considerable advancement in mathematics and electronics theory was required before the first modern computers could be designed.[citation needed]HomeEducation
The Evolution of the Computer1. First Generation (1939-1954) - vacuum tube 1937 - John V. Atanasoff designed the first digital electronic computer 1939 - Atanasoff and Clifford Berry demonstrate in Nov. the ABC prototype 1941 - Konrad Zuse in Germany developed in secret the Z3 1943 - In Britain, the Colossus was designed in secret at Bletchley Park to decode German messages 1944 - Howard Aiken developed the Harvard Mark I mechanical computer for the Navy 1945 - John W. Mauchly and J. Presper Eckert built ENIAC at U of PA for the U.S. Army 1946 - Mauchly and Eckert start Electronic Control Co., received grant from National Bureau of Standards to build a ENIAC-type computer with magnetic tape input/output, renamed UNIVAC in 1947 but run out of money, formed in Dec. 1947 the new company Eckert-Mauchly Computer Corporation (EMCC). 1948 - Howard Aiken developed the Harvard Mark III electronic computer with 5000 tubes 1948 - U of Manchester in Britain developed the SSEM Baby electronic computer with CRT memory 1949 - Mauchly and Eckert in March successfully tested the BINAC stored-program computer for Northrop Aircraft, with mercury delay line memory and a primitive magentic tape drive; Remington Rand bought EMCC Feb. 1950 and provided funds to finish UNIVAC 1950- Commander William C. Norris led Engineering Research Associates to develop the Atlas, based on the secret code-breaking computers used by the Navy in WWII; the Atlas was 38 feet long, 20 feet wide, and used 2700 vacuum tubes 1951 - S. A. Lebedev developed the MESM computer in Russia 1951 - Remington Rand successfully tested UNIVAC March 30, 1951, and announced to the public its sale to the Census Bureau June 14, 1951, the first commercial computer to feature a magnetic tape storage system, the eight UNISERVO tape drives that stood separate from the CPU and control console on the other side of a garage-size room. Each tape drive was six feet high and three feet wide, used 1/2-inch metal tape of nickel-plated bronze 1200 feet long, recorded data on eight channels at 100 inches per second with a transfer rate of 7,200 characters per second. The complete UNIVAC system weighed 29,000 pounds, included 5200 vacuum tubes, and an offline typewriter-printer UNIPRINTER with an attached metal tape drive. Later, a punched card-to-tape machine was added to read IBM 80-column and Remington Rand 90-column cards. 1952 - Remington Rand bought the ERA in Dec. 1951 and combined the UNIVAC product line in 1952: the ERA 1101 computer became the UNIVAC 1101. The UNIVAC I was used in November to calculate the presidential election returns and successfully predict the winner, although it was not trusted by the TV networks who refused to use the prediction. 1954 - TheSAGEaircraft-warning system was the largest vacuum tube computer system ever built. It began in 1954 at MIT's Lincoln Lab with funding from the Air Force. The first of 23 Direction Centers went online in Nov. 1956, and the last in 1962. Each Center had two 55,000-tube computers built by IBM, MIT, AND Bell Labs. The 275-ton computers known as "Clyde" were based on Jay Forrester's Whirlwind I and had magnetic core memory, magentic drum and magnetic tape storage. The Centers were connected by an early network, and pioneered development of the modem and graphics display.
2.Second Generation Computers (1954 -1959) - transistor
1950 - National Bureau of Standards (NBS) introduced its Standards Eastern Automatic Computer (SEAC) with 10,000 newly developed germanium diodes in its logic circuits, and the first magnetic disk drive designed by Jacob Rabinow 1953 -Tom Watson, Jr.,led IBM to introduce the model 604 computer, its first with transistors, that became the basis of the model 608 of 1957, the first solid-state computer for the commercial market. Transistors were expensive at first, cost $8 vs. $.75 for a vacuum tube. But Watson was impressed with the newtransistor radiosand gave them to his engineers to study. IBM also developed the 650 Magnetic Drum Calculator, the first by IBM to use magnetic drum memory rather punched cards, and began shipment of the 701 scientific "Defense Calculator" that was the first of the Model 700 line that dominated main frame computers for the next decade 1955 - IBM introduced the 702 business computer; Watson on the cover ofTimemagazine March 28 1956 - Bendix G-15A small business computer sold for only $45,000, designed by Harry Huskey of NBS 1959 - General Electric Corporation delivered its Electronic Recording Machine Accounting (ERMA) computing system to the Bank of America in California; based on a design by SRI, the ERMA system employed Magnetic Ink Character Recognition (MICR) as the means to capture data from the checks and introduced automation in banking that continued with ATM machines in 1974
3. Third Generation Computers (1959 -1971) - IC 1959 - Jack Kilby of Texas Instruments patented the first integrated circuit in Feb. 1959; Kilby had made his first germanium IC in Oct. 1958; Robert Noyce at Fairchild used planar process to make connections of components within a silicon IC in early 1959; the first commercial product using IC was the hearing aid in Dec. 1963; General Instrument made LSI chip (100+ components) for Hammond organs 1968 1964 - IBM produced SABRE, the first airline reservation tracking system for American Airlines; IBM announced the System/360 all-purpose computer, using 8-bit character word length (a "byte") that was pioneered in the 7030 of April 1961 that grew out of the AF contract of Oct. 1958 following Sputnik to develop transistor computers for BMEWS 1968 - DEC introduced the first "mini-computer", the PDP-8, named after the mini-skirt; DEC was founded in 1957 by Kenneth H. Olsen who came for the SAGE project at MIT and began sales of the PDP-1 in 1960 1969 - Development began on ARPAnet, funded by the DOD 1971 - Intel produced large scale integrated (LSI) circuits that were used in the digital delay line, the first digital audio device
4. Fourth Generation (1971-Present) - microprocessor 1971 - Gilbert Hyatt at Micro Computer Co. patented the microprocessor; Ted Hoff at Intel in February introduced the 4-bit 4004, a VSLI of 2300 components, for the Japanese company Busicom to create a single chip for a calculator; IBM introduced the first 8-inch "memory disk", as it was called then, or the "floppy disk" later; Hoffmann-La Roche patented the passive LCD display for calculators and watches; in November Intel announced the first microcomputer, the MCS-4; Nolan Bushnell designed the first commercial arcade video game "Computer Space" 1972 - Intel made the 8-bit 8008 and 8080 microprocessors; Gary Kildall wrote his Control Program/Microprocessor (CP/M) disk operating system to provide instructions for floppy disk drives to work with the 8080 processor. He offered it to Intel, but was turned down, so he sold it on his own, and soon CP/M was the standard operating system for 8-bit microcomputers; Bushnell created Atari and introduced the successful "Pong" game 1973 - IBM developed the first true sealed hard disk drive, called the "Winchester" after the rifle company, using two 30 Mb platters; Robert Metcalfe at Xerox PARC created Ethernet as the basis for a local area network, and later founded 3COM 1974 - Xerox developed the Alto workstation at PARC, with a monitor, a graphical user interface, a mouse, and an ethernet card for networking 1975 - the Altair personal computer is sold in kit form, and influenced Steve Jobs and Steve Wozniak 1976 - Jobs and Wozniak developed the Apple personal computer; Alan Shugart introduced the 5.25-inch floppy disk 1977 - Nintendo in Japan began to make computer games that stored the data on chips inside a game cartridge that sold for around $40 but only cost a few dollars to manufacture. It introduced its most popular game "Donkey Kong" in 1981, Super Mario Bros in 1985 1978 - Visicalc spreadsheet software was written by Daniel Bricklin and Bob Frankston 1979 - Micropro released Wordstar that set the standard for word processing software 1980 - IBM signed a contract with the Microsoft Co. of Bill Gates and Paul Allen and Steve Ballmer to supply an operating system for IBM's new PC model. Microsoft paid $25,000 to Seattle Computer for the rights to QDOS that became Microsoft DOS, and Microsoft began its climb to become the dominant computer company in the world. 1984 - Apple Computer introduced the Macintosh personal computer January 24. 1987 - Bill Atkinson of Apple Computers created a software program called HyperCard that was bundled free with all Macintosh computers. This program for the first time made hypertext popular and useable to a wide number of 5. Fifth Generation (Present and Beyond) 1991 - World-Wide Web (WWW) was developed by Tim Berners-Lee and released by CERN. 1993 - The first Web browser called Mosaic was created by student Marc Andreesen and programmer Eric Bina at NCSA in the first 3 months of 1993. The beta version 0.5 of X Mosaic for UNIX was released Jan. 23 1993 and was instant success. The PC and Mac versions of Mosaic followed quickly in 1993. Mosaic was the first software to interpret a new IMG tag, and to display graphics along with text. Berners-Lee objected to the IMG tag, considered it frivolous, but image display became one of the most used features of the Web. The Web grew fast because the infrastructure was already in place: the Internet, desktop PC, home modems connected to online services such as AOL and Compuserve 1994 - Netscape Navigator 1.0 was released Dec. 1994, and was given away free, soon gaining 75% of world browser market. 1996 - Microsoft failed to recognized the importance of the Web, but finally released the much imporoved browser Explorer 3.0 in the summer. INPUT DEVICES a) Graphics Tabletsb) Camerasc) Video Capture Hardwared) Trackballse) Barcode readerf) Digital camerag) Gamepadh) Joysticki) Keyboardj) Microphonek) MIDI keyboardl) Mouse (pointing device)m) Scannern) Webcamo) Touchpadsp) Pen Inputq) Microphoner) Electronic WhiteboardOUTPUTDEVICES1. Monitor2. Printers (all types)3. Plotters4. Projector5. LCD Projection Panels6. Computer Output Microfilm (COM)7. Speaker(s)
Input and Output Devices
Before a computer can process your data, you need some method toinputthe data into the machine. The device you use will depend on what form this data takes (be it text, sound, artwork, etc.).Similarly, after the computer has processed your data, you often need to produceoutputof the results. This output could be a display on the computer screen,hardcopyon printed pages, or even the audio playback of music you composed on the computer.The terms input and output are used both as verbs to describe the process of entering or displaying the data, and as nouns referring to the data itself entered into or displayed by the computer.Below we discuss the variety of peripheral devices used for computer input and output.
Input DevicesKeyboard
The computerkeyboardis used to enter text information into the computer, as when you type the contents of a report. The keyboard can also be used to type commands directing the computer to perform certain actions. Commands are typically chosen from an on-screen menu using a mouse, but there are often keyboard shortcuts for giving these same commands.In addition to the keys of the main keyboard (used for typing text), keyboards usually also have a numeric keypad (for entering numerical data efficiently), a bank of editing keys (used in text editing operations), and a row of function keys along the top (to easily invoke certain program functions). Laptop computers, which dont have room for large keyboards, often include a fn key so that other keys can perform double duty (such as having a numeric keypad function embedded within the main keyboard keys).Improper use or positioning of a keyboard can lead to repetitive-stress injuries. Someergonomickeyboards are designed with angled arrangements of keys and with built-in wrist rests that can minimize your risk of RSIs.Most keyboards attach to the PC via a PS/2 connector or USB port (newer). Older Macintosh computers used an ABD connector, but for several years now all Mac keyboards have connected using USB.Pointing DevicesThe graphical user interfaces (GUIs) in use today require some kind of device for positioning the on-screen cursor. Typical pointing devices are: mouse, trackball, touch pad, trackpoint, graphics tablet, joystick, and touch screen.Pointing devices, such as a mouse, connected to the PC via aserial ports(old),PS/2mouse port (newer), orUSBport (newest). Older Macs used ADB to connect their mice, but all recent Macs useUSB(usually to a USB port right on the USB keyboard).MousePCKeyboard (you have one in front of you that you can see for a closer look)
Themousepointing device sits on your work surface and is moved with your hand. In older mice, a ball in the bottom of the mouse rolls on the surface as you move the mouse, and internal rollers sense the ball movement and transmit the information to the computer via the cord of the mouse.The neweroptical mousedoes not use a rolling ball, but instead uses a light and a small optical sensor to detect the motion of the mouse by tracking a tiny image of the desk surface. Optical mice avoid the problem of a dirty mouse ball, which causes regular mice to roll unsmoothly if the mouse ball and internal rollers are not cleaned frequently.Acordlessorwireless mousecommunicates with the computer via radio waves (often usingBlueToothhardware and protocol) so that a cord is not needed (but such mice need internal batteries).A mouse also includes one or more buttons (and possibly a scroll wheel) to allow users to interact with the GUI. The traditional PC mouse has two buttons, while the traditional Macintosh mouse has one button. On either type of computer you can also use mice with three or more buttons and a small scroll wheel (which can also usually be clicked like a button).Touch padTwo-button mouse with scroll wheel
Wireless Macintosh mouse
Most laptop computers today have atouch padpointing device. You move the on-screen cursor by sliding your finger along the surface of the touch pad. The buttons are located below the pad, but most touch pads allow you to perform mouse clicks by tapping on the pad itself.Touch pads have the advantage over mice that they take up much less room to use. They have the advantage over trackballs (which were used on early laptops) that there are no moving parts to get dirty and result in jumpy cursor control.TrackpointTouch pad of a PC laptop
Some sub-notebook computers (such as the IBM ThinkPad), which lack room for even a touch pad, incorporate atrackpoint, a small rubber projection embedded between the keys of the keyboard. The trackpoint acts like a little joystick that can be used to control the position of the on-screen cursor.TrackballTrackpoint
Thetrackballis sort of like an upside-down mouse, with the ball located on top. You use your fingers to roll the trackball, and internal rollers (similar to whats inside a mouse) sense the motion which is transmitted to the computer. Trackballs have the advantage over mice in that the body of the trackball remains stationary on your desk, so you dont need as much room to use the trackball. Early laptop computers often used trackballs (before superior touch pads came along).Trackballs have traditionally had the same problem as mice: dirty rollers can make their cursor control jumpy and unsmooth. But there are modern optical trackballs that dont have this problem because their designs eliminate the rollers.JoysticksTrackball
Joysticks and other game controllers can also be connected to a computer as pointing devices. They are generally used for playing games, and not for controlling the on-screen cursor in productivity software.Touch screenSome computers, especially small hand-held PDAs, have touch sensitive display screens. The user can make choices and press button images on the screen. You often use a stylus, which you hold like a pen, to write on the surface of a small touch screen.Graphics tablet
A graphics tablet consists of an electronic writing area and a special pen that works with it. Graphics tablets allows artists to create graphical images with motions and actions similar to using more traditional drawing tools. The pen of the graphics tablet is pressure sensitive, so pressing harder or softer can result in brush strokes of different width (in an appropriate graphics program).ScannersAscanneris a device that images a printed page or graphic by digitizing it, producing an image made of tiny pixels of different brightness and color values which are represented numerically and sent to the computer. Scanners scan graphics, but they can also scan pages of text which are then run through OCR (Optical Character Recognition) software that identifies the individual letter shapes and creates a text file of the page's contents.MicrophoneAmicrophonecan be attached to a computer to record sound (usually through a sound card input or circuitry built into the motherboard). The sound is digitizedturned into numbers that represent the original analog sound wavesand stored in the computer to later processing and playback.MIDI DevicesMIDI(Musical Instrument Digital Interface) is a system designed to transmit information between electronic musical instruments. A MIDI musical keyboard can be attached to a computer and allow a performer to play music that is captured by the computer system as a sequence of notes with the associated timing (instead of recording digitized sound waves).Graphics tablet.
Output DevicesCRT Monitor
The traditional output device of a personal computer has been theCRT(Cathode Ray Tube) monitor. Just like a television set (an older one, anyway) the CRT monitor contains a large cathode ray tube that uses an electron beam of varying strength to paint a picture onto the color phosphorescent dots on the inside of the screen. CRT monitors are heavy and use more electrical power than flat panel displays, but they are preferred by some graphic artists for their accurate color rendition, and preferred by some gamers for faster response to rapidly changing graphics.Monitorscreen sizeis measured diagonally across the screen, in inches. Not all of the screen area may be usable for image display, so the viewable area is also specified. Theresolutionof the monitor is the maximum number of pixels it can display horizontally and vertically (such as 800 x 600, or 1024 x 768, or 1600 x 1200). Most monitors can display several resolutions below its maximum setting.Pixels(short for picture elements) are the small dots that make of the image displayed on the screen. The spacing of the screens tiny phosphor dots is called thedot pitch(dp), typically .28 or .26 (measured in millimeters). A screen with a smaller dot pitch produces sharper images.Your computer must produce a video signal that a monitor can display. This may be handled by circuitry on the motherboard, but is usually handled by avideo cardin one of the computersexpansion slots; often the slot is a special one dedicated to video use, such as anAGPslot (Accelerated Graphics Port). Video cards are also calledvideo display adapters, andgraphics cards.Many video cards contain separate processors and dedicated video memory for generating complex graphics quickly without burdening the CPU. Theseaccelerated graphics cardsare loved by gamers.Flat Panel MonitorCRT monitor
Aflat panel displayusually uses anLCD(Liquid Crystal Display) screen to display output from the computer. The LCD consists of several thin layers that polarize the light passing through them. The polarization of one layer, containing long thin molecules called liquid crystals, can be controlled electronically at each pixel, blocking varying amounts of the light to make a pixel lighter or darker. Other types of flat panel technology exist (such asplasma displays) but LCDs are most commonly used in computers, especially laptops.Older LCDs had slow response times and low contrast, butactive matrixLCD screens have a transparent thin film transistor (TFT) controlling each pixel, so response, contrast, and viewing angle are much improved.Flat panel displays are much lighter and less bulky than CRT monitors, and they consume much less power. They have been more expensive than CRTs in the past, but the price gap is narrowing. You will see many more flat panels in the future.As with CRTs, the display size of a flat panel is expressed in inches, and the resolution is the number of pixels horizontally and vertically on the display.Ink Jet PrinterFlat panel display (LCD)
For hardcopy (printed) output, you need some kind of printer attached to your computer (or available over a network). The most common type of printer for home systems is the colorink jetprinter. These printers form the image on the page by spraying tiny droplets of ink from the print head. The printer needs several colors of ink (cyan, yellow, magenta, and black) to make color images. Some photo-quality ink jet printers have more colors of ink.Ink jet printers are inexpensive, but the cost of consumables (ink cartridges and special paper) make them costly to operate in the long run for many purposes.Laser PrinterInkjet Printer
Alaser printerproduces good quality images by the same technology that photocopiers use. A drum coated with photosensitive material is charged, then an image is written onto it by a laser (or LEDs) which makes those areas lose the charge. The drum then rolls throughtoner(tiny plastic particles of pigment) that are attracted to the charged areas of the drum. The toner is then deposited onto the paper, and then fused into the paper with heat.Most laser printers are monochrome (one color only, usually black), but more expensive laser printers with multiple color toner cartridges can produce color output.Laser printers are faster than ink jet printers. Their speed is rated inpages per minute(ppm). Laser printers are more expensive than ink jets, but they are cheaper to run in the long term if you just need good quality black & white pages.Other PrintersLaser Printer
Multi-function printers are available that not only operate as a computer printer, but also include the hardware needed to be a scanner, photocopier, and FAX machine as well.Dot matrixprinters use small electromagnetically activated pins in the print head, and an inked ribbon, to produce images by impact. These printers are slow and noisy, and are not commonly used for personal computers anymore (but they can print multi-layer forms, which neither ink jet or laser printers can).Sound Output
Computers also produce sound output, ranging from simple beeps alerting the user, to impressive game sound effects, to concert quality music. The circuitry to produce sound may be included on the motherboard, but high quality audio output from a PC usually requires asound cardin one of the expansion slots, connected to a set of good quality external speakers or headphones.Multimediais a term describing computer output that includes sound, text, graphics, movies, and animation.
CONCLUSION :I hope you have a better understanding of how the computer developed from giant machinery to something that fits in your hand. It took many people and over seventy years for the electronic computer to become what you know today. What once began as a giant calculator can now communicate with people around the world. Talk to your parents and grandparents about their first experience with computers. Many never touched a computer until high school or even college. Today computer technology is in almost everything.
