FLOPPY DISKETTES, HARD DISK

The floppy diskette is the most common and popular type of auxiliary storage. It provides computer system especially microcomputer system with the ability to read or retrieve information randomly. Diskettes are as real as paper files. Anything you can do with a paper file can be done with a disk file. This includes copying it. changing it, adding to it and changing its name. Floppy disks are flexible, made of oxide coated mylar and stored in a paper or plastic envelopes. The entire envelope is inserted in the disk unit, thus effectively protecting the contents of the disk surfaces. The disk surfaces are rotated inside the prtective covering. The disk head contacts the track positions through a solt in the covering. Recording is magnetic in conectric circles called tracks. These circles or track are divided into sectors. Each individual sector holds 512 bytes of data. Floppy or diskettes are available in three different sizes, the large size 8" diameter can hold information of the order of 360 kilohytes in the magnetic medium. The computer access the magnetic medium through the read/write opening. The index hole is used by the computer to properly align the diskette. Minifloppy diskette or 5.25" diameter floppy can hold information upto 1.2 megabytes while mircrofloppy diskette are of 3.5" diameter, and has capacity upto 1.44 megabytes. These drives and the diskettes used in them are referred to as "single sided/single density" or SS/SD, "single sided/double density" or SS/DD and also double sided/double density or DS/DD types. Generally microfloppy and minifloppy and assigned drive A and drive B respectively while the fixed hard disk drive is made the drive C. Various diskette deive configurations are used in addition to compact disk drive. They are housed in the system unit.

HARD DISK

Many computers contain a special type of disk called a fixed disk or hard disk. It is a high speed, large capacity disk and is referred as a mass storage magnetic medium that provides computer systems with the ability to read or retrieve informations sequentially or reandomly. The phsical characteristics of all magnetic recording material. Hard disks are faster and capable of storing much more information ranging in gigabytes. A typical hard disk unit consists or 6 circular disks fixed to a central shaft. Both surfaces of each plate are used to contain data except for the tep and bottom plaets. A set of disk plates can have 10 surfaces. For each recording surface there is a read/wirte head assembly. Each head can be positioned at any desired track/band on each surface. All the heads move together, therefore, the same recording band is selected on each recording surface at the same time. Thus for any single head movement the computer can access 10 bands of information.
LASER HOLOGRAPHIC STORAGE

COMPACT DISK AND DISC RECORDABLE

COMPACT DISK

CD Rom stand for Compact disc read only memory. These discs are cecoming popular now a days especially for use with microcomputers. The name implies to its application. Once inserted into the CD Rom driver, the text, video images and so on can be read into Ram for processing or display. However the data on the disc are fixed and cannot be altered this is in contrast to read/write capability of magnetic discs. CD Roms have tremendus storage capacity. The capacity of a single CD Rom is upto 680 Mbytes wquvalent to over 600 normal size books each of 500 pages or about 470 DS/HD diskettes. Magnetic disks store data in concentric tracks each of which is divided into sectors. The sectors on the inside tracks hold the same amount of information as those on the outside tracks. Although this wastes magnetic disk space, it optimized the speed at which data can be written and retrieved because a magnetic disk spins at a constant speed. In contras, CD Roms store data in a single track that spirals from the centre to the outside edge. The ultra thin track spirals around the disk thoudands of times. Data are recorded on the Roms reflective surface in the form of pits and lands. The pits or depressions are tiny reflective bumps that have been burned in with a laser beam. The pits are flat areas separating the pits. A land reflects the laser light into the sensor and a pit scatters the light. A spot that reflects the laser beam into the sensor is interpreted as a 1, and the absence of a reflection is interpreted as a 0. Together they record read only binary information that can be interpreted by the computer as text, audio, images and so on. Once the data have been recorded, a protective coating is applied to the reflective surface. The speed at which a given CD Rom spins depends upon the phsical location of the data being read. The data passes over the moveable laser detector at the same rate, no matter where the data are read. Therefore the CD Rom must spin more quickly when accessing data near the centre. Even though with the changing speed of the disk, reading data from an optical medium is a relatively simple matter, writing data is a different matter. The fact that you cannot write data to a CD Rom does not mean that this storage medium is not useful. Infact many applications rely on huge volumes of data that that rarely changes. For example, dictionaries, encyclopedias, medical, legal and other professional referance libraries, software packages, music and video all require termendous amount of data that you would not normally want to alter.

COMPACT DISC RECORDABLE

For large quantities, CD Rom disks can be produced by manufacturers with expensive duplication equipment. Nearly all the PCs have CR Rom drives. This rapid and universal acceptance of CD Rom has given rise to an exciting new technology CD R, compact disk recordable. A CD R disk is functionally equvalent to a pre recorded CD Rom. A locally developed CD R will paly in any CD Rom drive.

PRINTERS WORK WITH COMPUTER

DOT MATRIX PRINTERS

In dot matrix printer, each letter is formed with a series of dots. Standard characters are produced by a pin printer or 24 pin printer. A normal dot matrix printer has speeds varying form 50 to 600 characters per seconds. The carriage width of a printer also varies ranging from 80 columns to 132 columns. Thus standard width printer print 80 characters per line while the wide carriage printer prints 132 characters per line.

DAISY WHEEL PRINTERS

This printer uses a print mechanism in the form of a series of petals arranged on a petal wheel. A character is contained at the end of each petal. The wheel rotates to bring the desired character into position. An image formed when a hammer strike the desired character. Daisy wheels are available in several formats (bold letter, italics etc.). A daisy wheel printer is slower than a dot matrix machine because of the time required to turn the print wheel. However it produces high quality print.

LINE PRINTERS

Line Printers are used with minicomputers and mainframe computers. They print at very fast speed. Line printers print one complete line at a time and at speeds greater than 1000 lines per minute. Line printers may be further divided into drum printers and band or chain printers.

NON IMPACT PRINTERS

New methods are being used in the computer printer technology in order to attain better quality and higher speed. A number of non impact printer have been developed which produce a printed image without striking the paper. Non impact printer are much faster has impact printers and produce much less noise and print high quality characters. Some of the non impact type of printers are:

• Electrostatic Printers
• Electro Thermal Printers
• Ink jet Printers and
• Laser Printers

ELECTROSTATIC PRINTERS

Electrostatic printer are high speed line printers. On scanning by electric field, a charged image is formed on paper. This paper is passed through an inkfog. The ink adhered at charged spots, which is fixed on passing through the heated rollers, producing the final printed sheet.

ELECTRO THERMAL PRINTERS

Thermal printers are inexpensive, small and require low voltage or battery power to operate. Their drawbacks are that these are slow and can only print on a special heat sensitive waxy paper. The image formed on the waxy paper is burned by the printer. Moreover this burned in image fades with time on prolonged exposure to sunlight. Thermal printers were popular a few years ago and are still available because of their protable nature and low cost.

INK JET PRINTERS

Work in the same way as dot matrix printers except that ink jet printer have fine spray nozsles instead of tiny pins used in dot matrix print head. Nozzles spray a stream of ink onto the paper. Because the ink is put directly on the paper, therefore, these printers require ink in a reservoirs instead of ribbon. Since no mechanical movement is involved, hence these printers are much quieter and have speed of about 200 characters per second. Ink jet printers are also available which have more than one ink reservoir, each with a different colour. The colours can be chosen through software to allow the printer to print in a rainbow colour. Thus a full colour graphinc image from a computer screen can be obtained very quietly on paper.

LASER PRINTER

Laser printers are the fastes machines in the printer industry. These printers use laser and electrophotographic technology to achieve printing speeds greater than 20,000 lines per minutes. In laser printing, a software creates a bitmapped image of the page in the computer. This image is processed and transferred to the printer which activates a laser beam to secan image on positively charged photoconductive surface of a rotating drum. The spots written by the laser take up a negative electric charge. A positive charged toner material is attracted by the negatively charged area of the drum written by the laser beam. This develops an image on the drum. As the paper passes between the drum and a positively charged wire called the corona wire, the image is transferred on the paper. The paper then passed between two rollers where the dots of the toner forming the image get fused onto the paper under the combined effect of heat and pressure. The printed result from a laser printer is impressive and better than letter quality. An advantage of laser printers over daisy wheel printers is their ability to produce graphic. Depending upon the software graphic and text can be merged on one page. As far as noise is concerned, laser printers are quieter and much faster.

DOT MATRIX, DAISY WHEEL, LINE PRINTERS

WHICH FUNCTIONS OUTPUT DEVICES

OUTPUT DEVICES

Peripheral devices used to get information or result from a computer are called output devices. A number of output devices are available for use in computer systems and vaious cominations of them are found in common use. These include display units, printers. floppy drivers, hard disks and other display devices.

VIDEO MONITORS

The video display unit or video monitor is the most popular microcomputer output divice, primarily because it is fast, quiet and cheaper than a printing device. A video monitor consists of a cathode ray tube (CRT) which is a TV like secreen. The monitor is made specifically to display information and is very similar to a home TV except that it does not include the electronic circuits for receiving TV signals. A computer can communicate with the user through a video monitor by presenting the result/information in visual form. There are two types of monitors black and white or monochrome monitors and coloured monitors. Mononchrome monitors come in two varieties depending upon the shade of display, green and amber. There are basically two kinds of colour monitors composite and RGB. A composite monitor works the same way as colour TV set. An RGB monitor has three electron guns, a green gun and a blue gun. The image is sharper and more refined on an RGB than a composite monitor. Visual display devices fall mainly in two categories. Alphanumeric display units, which can display only text, others called graphic display devices. Visual display units also come in low resolutions medium resolution or high resolution graphic mode and can display graphics such as maps, charts, graphs, engineering drawings, animation figures and other types of pictorial information as well as alphabets and numerals.

PRINTERS

The printers are one of most useful output devices for use with a computer. Printers are used extremely mechanical peripherals to produce permanent output from the computer. These are classified into two main categories depending upon the type of print mechanism.

• Impact Printers
• Non Impact Printers

INPACT PRINTERS

Impact printers work like typewriters. These are further classififed into three types based on their spped of printing and number of characters perline. There are

• Dost Matrix Printers
• Daisy Wheel Printers
• Line Printers

continue...VIDEO MONITOR, PRINTERS

MICROPHONES AN VOICE RECOGNITION

MICROPHONES AN VOICE RECOGNITION

Everone's computer's fantasy is to be able to dictate a command to the computer through a microphone and have the computer execute the command on the screen. For this type of sound input, a digitized recording is required. All you need to make such a recording are a microphne and a sound card that translate theelectrical signal from the microphoe into a digitized from that the computer can sotre and process. Sound cards can also translate digitized sounds back into analog signals that can then be sent to the speakers. There is also a demand for translating spoken words into text much as there is a demand for translating handwriting into text. Translating voice to text is a capability known as voice recognition. With it you can speak to the computer rather than having to type and you can control the computer with simple commands such as "shut down" or "print". Voice recognition faces problems that includes the large number of words required for a commercially feasible system (5,000 to 10,000 words), individual differences in speech patterns between different conditions, background noise and determining when one word stops and another begins. For example it would be extermely difficult for a computer to understan the difference between "two" and "too", "check" and "cheque" because of the similarity in the way they are spoken. There are four basic steps involved in speech recognition:

1. Say the word when you speak into a microphone, each sound is braken down into its vareous frequency.
2. Digitize the word the sounds in each frequency are digitized so they can be manipulated.
3. Match the word the digitized version fo the word is matched against similarly formed templated in the system's electronic dictionary.
4. Display each words or paerform the command when a match is found, the word is displayed on a V.D.T or the appropriate command is performed. If no match is found, the speaker is asked to repeat the word.

A spech recognition system contains a software, a generic vacabulary database, and a high quality microphone with noise concelling capabilities. The cocabulary may be only a few hundred words to enable navigation around windows (exist, copy, drag mouse and so on) and spread sheet. Once you have installed the software, you would need to train the system to recognize your unique speech pattern. To train the system, we simply talk to it for at least 20 minutes. The system uses artificial intelligence techniques to learn our speech pattern and update the vocabulary database accordingly. The challenge for voice recognition software is to reduce a sound's meaning correctly from its context and to distinguish meaningful sound from background noise.

VOICE RECOGNITION

 

HOW CAN WORK THESE IMPORTANT FUNCTIONS

TRACKBALL

The user controls the cursor on the screen by rolling a plastic ball with the fingertip or wrist. To execute commands with a trackball, one or more buttons are pressed, much as is done with a mouse. To move the cursor around the screen you roll the ball with your thumb or finger. Because you dont't move the whole device, a trackball requires less space than a mouse, so trackball is a solution when space is limited and is popular among users of laptop computers. Trackball may vary in size, but most are approximately the size of a standard desk calculator and may be amounted on either side of the keyboard. For handicapped people who may have difficulty pressing keys on a stadard keyboard or using a mouse, the trackball may be the answer since it is not necessary to move the entire arm to use it.

ELECTRIC LIGHT PEN

It consists of a photo cell placed in a small tube which can sense a position on displau tube when the end of the pen is held against the screen. In specially designed display seceen, data can be entered with a light pen as shown. When this electric light pen is brought near the screen, the light emitted is sensed by the photo cell. The electrical response is communicated to the computer to determine the part of the displayed item which is exciting the photo. A spot appears on the display screen at the location determined by the position of the pen. A computer programme compares the dot position generated by the device with computer generated data.. In this way new data can be entered or existing data can be modified figure below shows the use of a light pen in conjunction with a graphic display terminal to enter information into the computer. There are many other input devices like video digitizer, voice recognizer, magnetic ink character reader (MICR), optical character reader (OCR), remote terminal used for E mail, graphic table, etc. which can be linked with the computer. This is the most exciting part of using a personal computer.

DIGITAL CAMERA

Digital cameras operate on the same basic principles as a basic camera, but are more suitable for desktop publishing. The primary difference between a basic camera and a digital camera is that they use different media capturing images. The traditional camera uses film, while the digital camera uses a charged coupled device (CCD). Once captured, images can be uploaded to a PC and used in countless applications.

TRACKBALL, ELECTRIC LIGHT, DIGITAL CAMERA

MOUS, JOY STICK, SCANNERS

TYPES OF KEYBOARD

There are two basic styles of keyboard commonly found eith micro computers. PC/XT style keyboards and AT style. The PC/XT style keyboard was first one developed by IBM. Later AT style was developed with a slightly different keyboard having 101 keys. Different manufacturers have developed diferent keyboards with slight alternation with keys ranging from 84 to 108 using different style.

MOUSE

A mouse is an input device. Unlike the keyboard where the information is typed, mouse is a pointing device and is used to select various option. A mouse consists of a small hand held unit with one, two or three buttons and a small ball at the bottom on which it can roll. As the mouse is moved across the desk on a mouse pad, it guides a small locator symbol (often an arrow, a cross hairs or a cursor) which moves across the screen. A mouse can also be used to draw pictures on the screen and edit text.

JOY STICK

Joystick is an input device, a small box with moving stick and buttons. It is generally found with micro computer and is used primarily for games, educational sofware and computer aided design (CAD) system. You manipulate the handle of the joystick to position the cursor and click on a button to send impulses to the computer. The joystick does not interfere with your view of the screen nor does it require the movement of an object like a mouse. A joystick is fun to use because of the speed with which it moves the cursor on the screen.

 SCANNERS

Image scanners convert any image into electronic from by shining light onto the image and sensing the intensity of the reflection at every point. Colour scanners use filters to separat the components of colour into the primary additive colours red, green and blue at each point. Red, green and blue and known as primary additive colours because they can by combined to create any other colour. The image scanner is useful because it translates printed imagtes into an electronic format that can be sotred in computer's memory. The soted image can be transferred into a paint programme or directly into a word processor. A flatbed scanner easily scan documents books or periodicals. Flatbed scanners have higher quality reproduction and can scan a page in a single pass. Scanners difers in resolution: the more dot a scanned image contained, the sharper it is. An inexpansive scanner produces images at about 300 dots per inch or 600 dpi. The more expensive scanners produce images at a higher resolution.

PC/XT, (CAD)

SOME DIFFERENT KIND PORTS

PORTS

A system board with its processor and memory unit can work only when linked to input/output storage and communication devices to receive data and communicate results of processing. Peripheral devices such as a keyboard, mouse, monitor and a printer come with a cable and a multiple connector. To link a device to the PC, you plug its connector into a receptacle called a port in much the same way you plug a lamp cord into an electrical outlet. A port is one of the entry lines coming into the computer. A port provides a direct link to the microcomputer's common electrical bus. Most computer have several types of ports, each with different capabilities and uses. External peripheral devices outside the processor unit can be linked to the processor via cable through either a serial port or a parallel port. The system board is normally designed with at least one of each plus a dedicated keyboard port. Some have a dedicated port for the mouse. When a port is not available, you will need to install a circuit board that includes the port you need.

SERIAL PORTS

A  serical port provides a connection for transmitting data one bit at a time. A serial port connects your computer to a device such as a modem, which requires two way data transmission, or to a device such as a mouse, which requires only one way data transmission, or to a device such as a mouse, which requires only one way data transmission. To connect a peripheral device to your computer through a serial port, both the device and your computer must have a serial port.

MOUSE PORTS

A mouse port is a special serial port that connects a mouse to a computer. The mouse port can be built into the main board or mounted on an expansion card. Many computers include a mouse port in addition to standard serial ports.

INPUT/OUTPUT DEVICES

To communicate with a computer, there must be convenient ways of transferring the data and instructions into the computer and getting the results out in an acceptable form. This is accomplished by the input/output devices or I/O devices. Input devices receive information from the outside, convert it from a form that is easily understandable by the user into a form that is acceptable for the computer. Output devices retrieve information from the computer memory. These input/output devices are similar to our senses, our limbs and our ability to speak to our brain.

PORTS, SERIAL PORTS

BUSES, DATA BUS, ADDRESS BUS & CONTROL BUS

BUSES

In big cities mass transit systems move large number of people from one place to their destinations. In the same way computer has a system that move large amount of bits in the form of electrical pulses from a specified source to a specified destination. In computer, the term bus refers that paths between the components of a comuter. In a computer the bus stops are the control unit, the arithmetic and logic unit, internal memory (RAM, ROM and other types of internal memory), and the device controllers that control the operation of the periperal devices. The bus is the common path way through which the processor send/receives data and commands to/from primaty and secondary storage and all input/output peripheral devices. The capacity of a computer bus depends on the number of data lines it contains. A bus iwth 8 lines can transport 8 bits at a time whereas a bus with 16 lines can transport 16 bits at a time. There are two main buses in a computer, the data bus and the address bus. The one that you hear the most about is the data bus, so when people just say 'the bus', they usually mean the data bus.

DATA BUS

The data bus is an electrical path that connects the central processing unit (CPU) memory, and  the other hardware devices on the motherboard. Actually, the bus is a group of parallel wires. The number of wirs in the bus affects, the speed at which data can travel between components, just as the number of lanes on a highway affects how long it takes people to get to their destinations. Because each wire can ransfer one bit at a time, an eight-wire bus can move eight bits at a time. A 16-bit bus can transfer two bytes and a 32-bit bus can transfer four bytes at a time. Buses are designed to match the capabilities of the devices attached to them. So when CPUs could send and receive only one bytes of data a time. As microcomputer technology improved, chips where built that could send and receive more data at once, and bus designes allowed a winder path through which the data could flow.

ADDRESS BUS

Second bus that is found in every microcomputer is the address bus. the address bus is a set to wires similar to the data bus, it connects only the CPU and memory, and all it carries are memory address. The reason that the address bus is important is that number of lines in it determines the maximum number of memory addresses. For example, one byte of data is enough to 300 represent different values. If the address bus could carry only eight bit at a time, the CPU could address only 300 bytes of memory.  Most of the early PC had 20 bit address buses, so the CPU could address only 20 bytes or 1 MB of data. Today, most CPUs have 32 bit address buses that can address 4 GB (over 4 billion bytes) of memory.

CONTROL BUS

From the internal memory unit, the instructions are transferred to the control unit, which directs the activities of all other units. The control unit sends out control commands to all the components of the system through the bus called the control bus. The control unit directs the transfer of data to the ALU from the internal memory unit for the actual processing within the ALU. Under the control of control unit, a two transfer of data results and the instructions occur between the intrernal memory and the secondary storage.

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RANDOM ACCESS MEMORY

RANDOM ACCESS MEMORY

RAM is a memory in which each element of information has its own address (location) and from which any element can be retrieved easily and quickly by using that address. It is a temporary memory of a computer used to store the data and instructions of the user when the computer is on. It is also called as Read-And-Write Memory (RAM) since the computer can store (write) data at any selected location (address) and at any subsequent time, retrive (read) the data. The contents arelost when the power to the computer is shut off. Thus RAM is active only when computer is one and is also referred as a volatile memory because the data stored in it disappears whenever the computer is switched off. However he RAM has the advantage of much better access time, higher transfer rate and simple interfacing. Generally RAM is meausred in K bytes or M bytes. Large RAM size provides larger amount of information which a computer can hold for processing and hence increases the processing speed. Random access memory plays an integral part in the internal operating of a processor. These three random access memory as well as read only memory, the control unit and arithmetic and logic unit work together.

READ ONLY MEMORY

The other type of memory contained in the computers is the read only Memory (ROM). This is a permanent memory of the computer designed by the manufacturers of the the computers. This is used to store the instructions required to control the basic input-output operations of the computer when it is first tured on. It is a semiconductor chip programmes stored in ROM are called firmware. ROM is a nonvolatile i.e. the contents of this type of memory are not lost when the computer is turned off.

SECONDARY MEMORY

Secondary storage or secondary memory also referred as backing storage is used to supplement the capacity of main storage. This memory stored a bulk of information. It is also called auxiliary storage or mass storage. The information stored in this memory is used by the CPU by first bringing it to main memory. Examples of secondary memory are magnetic disks, magnetic tape and mass cartridage systems. Secondary storage is two types: Sequential and Direct access.

SEQUENTIAL ACCESS

Access through sequential acces storage is non-addressable that is an operator cannot refer directly to the contents of a particular storage location such as that used with meagnetic tape. This involves examining sequentially all recorded data. This form of storage necessitates tape searching by starting at the beginning of the tqpe and continuing to search through all records until the desired information area is found.

DIRECT ACCESS STORAGE

Direct access storage is addressable that is a given item can be selected from anywhere in storage by simply specifying the address where it is located Direct access devices such as magnetic disks provide immediate access to individul records and do not require reading from the beginning of a file to find a particular record.

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KEY BOARD, MONITOR, CPU

KEY BOARD

The keyboard is one of the most useful input device. It provides a convenient way to feed data instructions into a computer. A computer keyboard is similar to an electric typewriter keyboard with slight modification having additional keys for specific functions. It can be easily plugged with computer. Its main function is to enable the user to communicate with the computer.

MONITOR

The monitor is the name commonly used for the visual display unit. It is the most useful output device through which a computer communicates with the user. A video monitor has a TV like screen, which displays both alphanumeric characters and graphics. It has rapidly become one of the most popular methods of displaying data/information.

C.P.U

The Control Unit is the most important part of the C.P.U as it controls and coordincates the activities of all other computer units. It performs this function by issuing necessary commands to various components of the computer. It also controls the input/output devices as well as the backing storage devices. Another aspect of the control function of the CPU is governed by the programme. A programme is a set of instructions in a sequence, which tells the computer what to do. The programme, written to solve a specific problem, instructs the computer system to perform mathematical calculations, input data, store data, display results on a visual device and so on. The flow of instructions, data and results is governed by the Control Unit, which sets the various logic gates, feeds the numerical data and provides the clock pulsees (heart beat of the computer) that regulates the speed of all the operations. Instructions received from input unit are stored in one part of the memory, while data is stored in another part. The Control Unit generates signals in accordance with the programme, the control signal or the control input provides a desired sequence of arithmetic operation and retrieves the numerical data from the memory.

COMPUER STORAGE

Computer storage also referred, as computer memory is actually an electronic file in which instructions and data are placed until needed. Computer storage is divided into two classes:

• Main storage or Main memory
• Secondary storage or Secondary memory

The major reason for the distinction between main and auxiliary storage is the cost in relation to performance and capacity. Main memory provides very fast performance or it is directly accessible by the CPU but is much more costly per unit of capacity than the auxiliary storage devices. Auxiliary storage provides maximum capacity for large data files.



MAIN MEMORY

Main memory is the computer's primary storage. It is an extension of the Central Processing Unit (CPU) and is directly accessible to it. Its function is controlled by the Control Unit, which sends READ or WRITE signal for the appropriate memory location. Main memory accepts data and instructions from the input unit, exchanges data with and supplies instructions to other parts of the Central Processing Unit (CPU). The memory unit also stores those instructions and data that are currently being used by the CPU or those instructions and data awaiting immediate execution. Its capacity must be sufficient to retain both the usable amount of data and instructins needed for processing it. Some operations require more instructins or data than can be held in main memory at one time. In such cases, main memory is supplemented with secondary storage. The capacity of a storage device is expressed as number of bits, characters or bytes. One byte is a group of eight bits that forms one character. A bit is a binary number used in digital computers, which stands for binary digit. One bit contains the minimum information and is a basic unit that has value 0 or 1. Thus if the memory of a computer is 32000 bytes, it means that it can store 32000 characters. Semiconductor storage (integrated circuits) and magnetic cores are the most widely used forms of main storage. Besides reduced size and increased speed, semiconductor storage offers the advantage of non-destructive read. There are vaious storage types available, which included RAM,ROM,PROM,EPROM, and EAROM. The most common kind of semiconductor storage is RAM (Random Access Memory) and ROM (Read only Memory).

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INTRODUCTION TO COMPUTER

INTRODUCTION TO COMPUTER

The computeris the most useful and versatile modern tool yet developed. It has changed the information needs of most people not only the people of advanced countries but even the people of third world countries, Computer has influenced the international trad, pattern of employment, industrial productivity, home life, entertainment, space exploration, health care, and education.

HISTORY AND DEVELOPMENT OF COMPUTER

The Computer has evolved naturally through centuries from early countin devices like the abacus. But today, instead of manipulating beads on a wire, we rely on electronic impulses to accomplish the same goals. As a result of technological innovations during the last fifty years computer has emerged as a most fast and powerful tool for scientists, engineers, doctors, architects, accountants, teacher, students to enhance their creativity and productivity in daily work. Rapid developments in electronic technology as made it feasible to

use computers for applications that would have been uneconomical only a few years ago.

Computers are capable of performing all kinds of tasks that sometimes seem magical in nature. In order to perform the simples job, computers need instructions from the users. Programming in the process of giving instructions to the computers so that the machine well execute the desired tasks. Programming is a way communicate with computers. A computer is an electronic computational device that has its own internal memory. It trads data when instructed, processes it and produces results accurately at a very high speed. A

computer along with a number of periperal units is collectively known as computer system. The work carried out by a computer system is often known as Electronic Data Processing (EDP) which means the use of electronic machine to drive result by means of arithmetic and logic operations from the data entered it. A computer system has two major divisions known as computer hardware and software.

COMPUTER HARDWARE

The hardware part of a computer system consist of physical components installed in a main computer box and all associated equipments interconnected in an organized way. Main unit which consist of a processing and control console in addition to disk drives is called the system unit. The devices such as keyboard, mouse, optical character Readr, MICR monitor, printer, etc. are linked with the system unit. These devices

send and retrieve information from the system unit. A computer system in general consists of three major units: (1)System unit (2) Input units and (3) Output units.

COMPUTER SOFTWARE

The techniques or methods which consist of the computer programs procedures and the paper work necessary to get the hardware to work is known as computer software. Computer software is the know how techniques in the form of a set of instructions that tells the computer what to do. It includes an operating system, which develops a link between the user and the computer system. It helps the user to communicate with the computer. Computer Software can further be divided into system software and application software predesigned programs are now available not only in printed form but also recorded on vaious types of magnetic surfaces or even on plug in modules or chips. These are called as firmware.

SYSTEM SOFTWARE

A set of programme required to implement certain functions in the computin system designed to control the operation of a computer system defines the system software. These programms are essential for a computer to function. Without these programms no interation is possible with computers. The system software is a general programme that helps the user in writing his/her application programme and makes the operation of the computer more effective and efficient. Usually this software is provided by the manufacturer.

APPLICATION SOFTWARE

Application software is the procedure written by the user to solve particular or to achieve specific results. Ready packages containing application software are also available easily for various purposes. These have specific applications for the users who are not familiar with any programming language or do not have the time to writen their own programme. These ready programms could be used to achieve specified objective more easily and quickly. Some of the application software categories are Word Processes, Spread Sheets, Database Management System, Drafting packages, and communication packages etc.

KEY BOARD, MONITOR, CPU