Index• Computer• Evolution of computer• Computer generations• Characteristics of computer• Uses of computer• Classification of computer• Computer organization
ComputerThe word “computer” comes from the word “compute”, which means, “to calculate”. Hence,people usually consider a computer to be a calculating device that can perform arithmeticoperations at high speed.A computer is a programmable machine designed to perform arithmetic and logical operationsautomatically and sequentially on the input given by the user and gives the desired output afterprocessing. However, more than 80% of work done by computers today is of non-mathematicalor non-numerical nature.More accurately, we can define a computer as a device that operates upon data. Data can beanything. It comes in various shapes and sizes depending upon the type of computer application.A computer can store, process and retrieve data as and when required. The fact that thecomputer processes data is so fundamental that many people have started calling it a dataprocessor.There are various ways in which computer can be defined but on the basis of its power the mostgeneralized and popular definition is -“A computer is an electronic device which processes or manipulates the data strictly accordingto the instructions given and produces meaningful result efficiently, effectively and reliably.”“Computer can be defined as any machine, which can accept data, in prescribed form, processthe data and supply the result of processing in a specified format as information or as signals tocontrol automatically some further machine or process.” - Dictionary of Computers – Penguin
Evolution of computersLike civilizations, computers have also evolved over a period of time. Some of the importantstages of computer evolution are listed below: Abacus is considered the earliest calculating device invented around 600 B.C., it is a rack of beads used to add or subtract by positioning the beads correctly. In 1642, Blaise Pascal invented first mechanical adding machine. The innovation and invention continued according to the needs of people. In 1822, a Professor of Cambridge University, Charles Babbage Known as father of computer, invented “Difference Engine” which can produce reliable tables, as at that time mathematical and statistical tables were prepared by the clerks which consumed lot of precious time and was also very much prone to errors. In 1942, he designed new machine “Analytical Engine” which was planned to be fully automatic and capable of performing all basic arithmetic calculations. Somehow this machine was not produced. But his idea gave most basic fundamentals of computer design. In 1937, Haward Aiken of Harvard University, in collaboration with IBM developed “Mark I” the punch card operated machine which could perform all the arithmetic calculations. In 1943, ENIAC (Electronic Numerical Integrator and Calculator) was developed by a design team headed by Professor Prosper Eckert and John Mauchly of Moore College of Engineering, University of Pennsylvania. ENIAC was very complex to be programmed but it was capable of performing calculations more than 200 times of Mark I. In 1946, Professor Jon Von Neumann developed EDAVC (Electronic Discrete Variable Automatic Computer). This computer stored the data and instructions in sequence, in memory in the binary form (0 & 1). For this reason, modern computers are known as digital computers.
UNIVAC (Universal Automatic Computer) was first digital computer installed in Census Bureau in 1951. By this time evolution was carried out at different places, but IBM (International Business Machine) came out first and produced machines for business. Computer GenerationsGeneration Years Switching Storage Switching MTBF Software Application Device Device TimeFirst 1949- Vacuum Tubes Acoustic delay 0.1 – 1 30 Machine Mostly scientific. 1955 lines, mille minutes and Later simple magnetic second to 1 Hr assembly business systems. drum. 1 languages. Kbytes Simple memory monitors.Second 1956- Transistors Magnetic core 1 – 10 About High level Extensive business 1965 main memory, micro 10 Hrs languages, applications. tapes and disk second FORTRAN, Engineering design peripheral COBOL, optimization memory. 100 Algol, scientific research. Kb main Batch memory. Operating SystemThird 1966- Integrated High speed 0.1 – 1 About FORTRAN Database 1975 Circuits(IC) magnetic micro 100 Hrs 4, COBOL management cores. Large second 68, PL/I system. Online disks (100 Timeshared systems. MB) 1MB Operating main memory. SystemFourth- I 1975- Large Scale Semiconducto 10 – 100 About FORTRAN PersonalPhase 1984 Integrated r memory. nano 1000 &&, Pascal, computers. Circuits Winches disk. second Hrs ADA, Distributed Microprocessors 10 MB main COBOL 74, systems. Integrated memory. Concurrent CAD/CAM real
1000MB Pascal time control. disks. Graphic oriented system.Fourth – II 1985- Very Large Semiconducto 1 – 10 About C, C++. SimulationPhase Present Scale Integrated r memory. 1 nano 10000 JAVA, visualization, Circuits. Over 3 GB main second Hrs PROLOG, Parallel computing, million memory. 100 FP Virtual reality, transistor per GB disk. Multimedia. chip *MTBF - Mean time between failures of processor.
Characteristics of ComputerSpeedComputers work at an incredible speed. A powerful computer is capable of performing about 3-4 million simple instructions per second.Accuracy
In addition to being fast, computers are also accurate. Errors that may occur can almost alwaysbe attributed to human error (inaccurate data, poorly designed system or faulty instructions /programs written by the programmer)DiligenceUnlike human beings, computers are highly consistent. They do not suffer from human traits ofboredom and tiredness resulting in lack of concentration. Computers, therefore, are better thanhuman beings in performing voluminous and repetitive jobs.VersatilityIt means the capacity to perform completely different type of work. You may use your computerto prepare payroll slips. Next moment you may use it for inventory management or to prepareelectric bills.StorageThe Computer has an in-built memory where it can store a large amount of data. You can alsostore data in secondary storage devices such as pen drive, DVD, CD, etc. which can be keptoutside your computer and can be carried to other computers.No IQComputer is a dumb machine and it cannot do any work without instruction from the user. Itperforms the instructions at tremendous speed and with accuracy. It is you to decide what youwant to do and in what sequence. So a computer cannot take its own decision as you can.No FeelingIt does not have feelings or emotion, taste, knowledge and experience. Thus it does not get tiredeven after long hours of work. It does not distinguish between users.Uses of ComputerEducation:Getting the right kind of information is a major challenge as is getting information to makesense. College students spend an average of 5-6 hours a week on the internet. Research shows
that computers can significantly enhance performance in learning. Students exposed to theinternet say they think the web has helped them improve the quality of their academic researchand of their written work. One revolution in education is the advent of distance learning. Thisoffers a variety of internet and video-based online courses.Health and Medicine:Computer technology is radically changing the tools of medicine. All medical information cannow be digitized. Software is now able to computer the risk of a disease. Mental healthresearchers are using computers to screen troubled teenagers in need of psychotherapy. Apatient paralyzed by a stroke has received an implant that allows communication between hisbrain and a computer; as a result, he can move a cursor across a screen by brainpower andconvey simple messages.Science:Scientists have long been users of computer. A new adventure among scientists is the idea of a“collaboration”, an internet based collaborative laboratory, in which researchers all over theworld can work easily together even at a distance. An example is space physics where spacephysicists are allowed to band together to measure the earth’s ionosphere from instruments onfour parts of the world.Business:Business clearly sees the interest as a way to enhance productivity and competitiveness. Someareas of business that are undergoing rapid changes are sales and marketing, retailing, banking,stock trading, etc. Sales representatives not only need to be better educated and moreknowledgeable about their customer’s businesses, but also must be comfortable with computertechnology. The internet has become a popular marketing tool. The world of cybercash hascome to banking – not only smart cards but internet banking, electronic deposit, bill paying,online stock and bond trading, etc.Recreation and Entertainment:Our entertainment and pleasure-time have also been affected by computerization. For example:
i) In movies, computer generated graphics give freedom to designers so that special effects andeven imaginary characters can play a part in making movies, videos, and commercials.ii) In sports, computers compile statistics, sell tickets, create training programs and diets forathletes, and suggest game plan strategies based on the competitor’s past performance.iii) In restaurants, almost every one has eaten food where the clerk enters an order by indicatingchoices on a rather unusual looking cash register; the device directly enters the actual data into acomputer, and calculates the cost and then prints a receipt.Government:Various departments of the Government use computer for their planning, control and lawenforcement activities. To name a few – Traffic, Tourism, Information & Broadcasting,Education, Aviation and many others.Defense:There are many uses computers in Defense such as:1) Controlling UAV or unmanned air-crafts an example is Predator. If you have cable I wouldrecommend watching the shows “Future Weapons" and “Modern Marvels". The show futureweapon gives an entire hour to the predator.2) They are also used on Intercontinental Ballistic Missiles (ICBMs) that uses GPS andComputers to help the missile get to the target.3) Computers are used to track incoming missiles and help slew weapons systems onto theincoming target to destroy them.4) Computers are used in helping the military find out where all their assets are (SituationalAwareness) and in Communications/Battle Management Systems.5) Computers are used in the logistic and ordering functions of getting equipments to andaround the battlefield.
6) Computers are used in tanks and planes and ships to target enemy forces, help run theplatform and more recently to help diagnose any problems with the platforms.7) Computers help design and test new systems.Sports:In todays technologically growing society, computers are being used in nearly every activity.Recording InformationOfficial statistics keepers and some scouts use computers to record statistics, take notes and chatonline while attending and working at a sports event.Analyzing MovementsThe best athletes pay close attention to detail. Computers can slow recorded video and allowpeople to study their specific movements to try to improve their tendencies and repair poorhabits.WritersMany sportswriters attend several sporting events a week, and they take their computers withthem to write during the game or shortly after while their thoughts are fresh in their mind.ScoreboardWhile some scoreboards are manually updated, most professional sports venues have verymodern scoreboards that are programmed to update statistics and information immediately afterthe information is entered into the computer.Safety and SecurityComputers have aided in the design of safety equipment in sports such as football helmets toshoes to mouth guards. Computer becomes an integral part for security. Many security systemshave been developed and used through computers.
• Analog ComputersAnalog Computer is a computing device that works on continuous range of values. The resultsgiven by the analog computers will only be approximate since they deal with quantities thatvary continuously. It generally deals with physical variables such as voltage, pressure,temperature, speed, etc.• Digital ComputerA computer that performs calculations and logical operations with quantities represented asdigits, usually in the binary number system i.e. 1 and 0.• Hybrid Computer (Analog + Digital)A combination of computers those are capable of inputting and outputting in both digital andanalog signals. A hybrid computer system setup offers a cost effective method of performingcomplex simulations.On the basis of Purpose• General Purpose ComputersThe general purpose computers are designed to solve a large variety of applications through theuse of stored program/instructions in its internal storage. However, this versatility is achieved atthe expense of speed and efficiency of the computer. Most digital computers are generalpurpose computers.• Special Purpose ComputersThese are built to solve a specific problem. In these machines, the computer program forsolving the problem is built right into the computer. Their operations are specific and areusually made for a single customer. Some examples are: automatic teller machine (ATM) for 24hours banking, industrial process system, etc.On the basis of Size and Capacity• Super Computers
Large scientific and research laboratories as well as the government organizations have extraordinary demand for processing data which required tremendous processing speed, memory andother services which may not be provided with any other category to meet their needs.Therefore very large computers used are called Super Computers. These computers areextremely expensive and the speed is measured in billions of instructions per seconds.Supercomputers are mainly being used for whether forecasting, biomedical research, remotesensing, aircraft design and other areas of science and technology. Examples of supercomputersare CRAY YMP, CRAY2, NEC SX-3, CRAY XMP and PARAM from India.• Main Frame ComputersThe most expensive, largest and the most quickest or speedy computer are called mainframecomputers. These computers are used in large companies, factories, organizations etc. themainframe computers are the most expensive computers; they cost more than 20 million rupees.In these computers 150 users are able to work on one C.P.U. The mainframes are able toprocess 1 to 8 bits at a time. They have several hundreds of megabytes of primary storage andoperate at a speed measured in nano second.
• Mini ComputersMini computers are smaller than mainframes, both in size and other facilities such as speed,storage capacity and other services. They are versatile that they can be fitted where ever they areneeded. Their speeds are rated between one and fifty million instructions per second (MIPS).They have primary storage in hundred to three hundred megabytes range with direct accessstorage device.• Micro ComputersThese are the smallest range of computers. They were introduced in the early 70’s having less
storing space and processing speed. Micro computers of today are equivalent to the minicomputers of yesterday in terms of performing and processing. They are also called “computerof a chip” because its entire circuitry is contained in one tiny chip. The micro computers have awide range of applications including uses as portable computer that can be plugged into anywall. It includes:Desktop Computer: a personal or micro-mini computer sufficient to fit on a desk.Laptop Computer: a portable computer complete with an integrated screen and keyboard. It isgenerally smaller in size than a desktop computer and larger than a notebook computer.Palmtop Computer/Digital Diary /Notebook /PDAs: A hand-sized computer. Palmtops haveno keyboard but the screen serves both as an input and output device.
Computer Organization Basic Computer OrganizationInput UnitThe first step in any processing activity is providing data and the instructions for processing thedata. Since computer cannot understand human language, therefore this communication has tobe done in a language which computer can understand. The unit that perform this task ofcommunicating data and instructions to the computer is referred to as Input Unit. This data is ina coded form (human understandable form), on an input medium and is read and translated byan input device into a form which is understandable by computer i.e. binary form.
Some of the input devices are as follows:• The MouseMouse is an input device that is used with personal computer. Earlier it rolls on a small ball butnow uses optical technology and has two or three buttons on the top. When you roll the mouseacross a flat surface the screen censors the mouse in the direction of mouse movement. Thecursor moves very fast with mouse giving you more freedom to work in any direction. It iseasier and faster to move through a mouse.• The KeyboardThis is the standard input device attached to all computers. The layout of keyboard is just likethe traditional typewriter of the type QWERTY. It also contains some extra command keys andfunction keys. It contains a total of 101 to 104 keys. You have to press correct combination ofkeys to input data. The computer can recognize the electrical signals corresponding to thecorrect key combination and processing is done accordingly.• Tracker Balls
Track ball is similar to the upside - down design of the mouse. The user moves the ball directly,while the device itself remains stationary. The user spins the ball in various directions to effectthe screen movements.• ScannersScanners are used to enter information directly in to the computers memory. This device workslike a Xerox machine. The scanner converts any type of printed or written information includingphotographs into digital pulses, which can be manipulated by the computer.• Touch PadsA touch pad is a laptop / palmtop device and responds to pressure. Conjunction with a specialpen they can be used by graphic artists wishing to create original, digital artwork.• Light Pens
It is a pen shaped device used to select objects on a display screen. It is quite like the mouse (inits functionality) but uses a light pen to move the pointer and select any object on the screen bypointing to the object.• JoysticksMany games require a joystick to play the game. Any different types, but it may be worthinvesting in a good quality one that is strong to withstand the rough treatment it will get fromthe kids while they are playing the games and one that can respond to movement in three axisdirections.• MicrophonesThis micro phone is used to convert human speech into electric signals. The signal pattern isthen transmitted to a computer when it’s compared to a dictionary of patterns that have beenpreviously placed in a storage unit of computer. When a close match is found, the word isrecognized.
• Web CamsSmall digital movie camera (a web cam) is mounted on the PC monitor to allow two waycommunication involving not just text communication, but sound and video as well.• Digital CamerasIt converts graphics directly into digital form. It looks like an ordinary camera, but no film isused therein, instead a CCD (changed coupled Divide) Electronic chip in used. When light falls,on the chip though the lens, it converts light waves into electrical waves.• Bar Code ReaderThis device reads bar codes and coverts them into electric pulses to be processed by a computer.A bar code is nothing but data coded in form of light and dark bars.
Output UnitThe data and instruction fed into the system through input unit go to memory of the computer.The data is processed according to the instructions given and result is again stored in memory ofthe computer in the form of binary digits 0 and 1. These results have to be communicated to theoutside world in human acceptable form. This function of communicating (through conversion)the result of processing to the human being for decision making is performed by Output Unit.Here are some most common output devices given below:• Visual Display UnitThe most popular input/output device is the Visual Display Unit (VDU). It is also called themonitor. A Keyboard is used to input data and Monitor is used to display the input data and toreceive massages from the computer. A monitor has its own box which is separated from themain computer system and is connected to the computer by cable. In some systems it is compactwith the system unit. It can be color or monochrome.• PrinterIt is an important output device which can be used to get a printed copy of the processed text orresult on paper. There are different types of printers that are designed for different types of
applications. Depending on their speed and approach of printing, printers are classified asimpact and non-impact printers. Impact printers use the familiar typewriter approach ofhammering a typeface against the paper and inked ribbon. Dot-matrix printers are of this type.Non-impact printers do not hit or impact a ribbon to print. They use electro-static chemicals andink-jet technologies. Laser printers and Ink-jet printers are of this type. This type of printers canproduce color printing and elaborate graphics.• PlotterPlotters are used to print graphical output on paper. It interprets computer commands and makesline drawings on paper using multicolored automated pens. It is capable of producing graphs,drawings, charts, maps etc.• Audio Output: SpeakersThe Audio output is the ability of the computer to output sound. Two components are needed:Sound card – Plays contents of digitized recordings, Speakers – Attached to sound card.• Projector
An output device that takes the display of a computer screen and project a large version of itonto a flat surface. Projectors are often used in meetings and presentations to help make sureeveryone in the room can view the presentation.Storage UnitData and instructions entered into a computer system through input units have to be storedinside the computer before actual processing starts. Similarly, results produced by the computerafter processing have to be kept somewhere inside the computer system before being passed onto an output unit. Moreover, a computer must also preserve intermediate results for ongoingprocessing. Storage unit of a computer system caters to all these need. It provides space forstoring data and instructions, intermediate results, and the results for output.Storage unit of all computers is comprised of the following two types of storage:Primary StoragePrimary storage, also known as main storage or memory, is used to hold pieces of programinstruction and data, intermediate result of processing, and recently produced result of thosejobs on which computer is currently working. These pieces of information are representedelectronically in the main memory chip’s circuitry and while it remains in the main memory,CPU can access it directly at a very fast speed. It is volatile in nature i.e. as soon as thecomputer is switched off or reset, the information hold by it is erased. Primary storage normallyhas limited storage capacity and is very expensive. In modern computers it is made up ofsemiconductors.It is of two types:• Random Access Memory (RAM)
Random Access Memory (RAM) is the best known form of computer memory. The Read andwrite (R/W) memory of a computer is called RAM. The RAM is a volatile memory; it meansinformation written to it can be accessed as long as power is on. As soon as the power is off, itcan not be accessed. RAM holds data and processing instructions temporarily until the CPUneeds it. RAM is considered “random access” because you can access any memory cell directlyif you know the row and column that intersect at that cell. RAM is made in electronic chipsmade of so called semiconductor material, just like processors and many other types of chips.• Read Only Memory (ROM)One major type of memory that is used in PCs is called read - only memory or ROM for short.ROM is a type of memory that normally can only be read, as opposed to RAM which can beboth read and written. There are two main reasons that read-only memory is used for certainfunctions within the PC:Permanence: The values stored in ROM are always there, whether the power is on or not. AROM can be removed from the PC, stored for an indefinite period of time, and then replaced,and the data it contains will still be there. For this reason, it is called non-volatile storage.Security: The fact that ROM cannot easily be modified provides a measure of security againstaccidental (or malicious) changes to its contents.Secondary StorageSecondary Storage of a computer is also known as auxiliary storage, is used to take care of thelimitations of primary storage. That is, it supplements the limited storage capacity and volatile
characteristic of primary storage. This is much cheaper than the primary storage and can retaininformation even when the computer switches off or resets. Secondary storage holds theprogram instructions, data and information of those jobs on which the computer system is notcurrently working but needs to hold them for processing later.The different types of secondary storage devices are currently in use are as follows:Arithmetic and Logic Unit
This unit performs the arithmetic and logical operations on the data and instructions supplied bythe input devices, under the command from the control unit. The basic arithmetic operationsperformed are addition, subtraction, multiplication and division, which are built into the controlunit. In addition to arithmetic operations computer can perform logical operations as well e.g.comparing two or more numbers or letters, making decision according to the defined criteria,etc. this is a place where data is manipulated and the result are communicated to memory.Control UnitThis is the most important unit in a computer system. It supervises the entire operation of acomputer system; it acts as a traffic policeman, which controls the traffic of data and electronicsignals between various units and components of computer. It instructs the input device when tostart and stop the input to memory, it transfer the input information from memory to arithmeticand logic unit, it selects the proper operations to be carried out, it directs the memory unit whento start and stop the transfer of information to output unit, etc. therefore the function of controlunit in a computer is to maintain order and direct the flow of operations in a proper manner. Itacts like central nervous system for various units of a computer.Central Processing UnitControl Unit, Arithmetic Logic Unit of a computer system are together known as CentralProcessing Unit (CPU). The CPU is the brain of a computer system. In human body, the braintakes all major decisions and other part of the body function as directed by the brain. Similarly,in a computer system, all major calculations and comparisons takes place inside the CPU andthe CPU is responsible for activating and controlling the operations of other units of thecomputer system.
BibliographyBooks of Reference:• Sinha P.K., Sinha Priti, “Computer Fundamentals”, BPB Publications, New Delhi, Fourth Edition ( revised and reprinted), 2010.• Saini A.K., Kumar Pradeep, “Computer Applications in Management”, Anmol Publications Pvt. Ltd., New Delhi, 2009.Websites of Reference:• http://www. ecomputernotes.com• http://www.kkhsou.in• http://en.wikipedia.org• http://www.google.co.in/imghp?hl=en&tab=wi