BASICS OF COMPUTER

BASICS OF COMPUTER

 

Commonly

Operated

Machine

Particularly

Used   for

Trade

Educational           

  and

Research.

Definition :

                   Computer is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. (Or) It is an electronic device that receives input, stores or processes the input as per user instructions and provides output in desired format.

Input-Process-Output Model  :

                     Computer input is called data and the output obtained after processing it, based on user’s instructions is called information. Raw facts and figures which can be processed using arithmetic and logical operations to obtain information are called data.

Characteristics of Computer  :

To understand why computers are such an important part of our lives, let us look at some of its characteristics −

·  Speed − Typically, a computer can carry out 3-4 million instructions per second.

·     Accuracy − Computers exhibit a very high degree of accuracy. Errors that may occur are usually due to inaccurate data, wrong instructions or bug in chips – all human errors.

·    Reliability − Computers can carry out same type of work repeatedly without throwing up errors due to tiredness or boredom, which are very common among humans.

·    Versatility − Computers can carry out a wide range of work from data entry and ticket booking to complex mathematical calculations and continuous astronomical observations. If you can input the necessary data with correct instructions, computer will do the processing.

·   Storage Capacity − Computers can store a very large amount of data at a fraction of cost of traditional storage of files. Also, data is safe from normal wear and tear associated with paper.

 Advantages of Using Computer :

·        Computers can do the same task repetitively with same accuracy.

·        Computers do not get tired or bored.

·       Computers can take up routine tasks while releasing human resource for more intelligent functions.

Disadvantages of Using Computer :

·    Computers have no intelligence; they follow the instructions blindly without considering the outcome.

·   Regular electric supply is necessary to make computers work, which could prove difficult everywhere especially in developing nations.

Generations of Computer :

          Let us now discuss the development in Computer Technology over the different generations.

 

First Generation

·  The period 1940 to 1956, roughly considered as the First Generation of Computer.

·  The first generation computers were developed by using vacuum tube or thermionic valve machine.

·     The input of this system was based on punched cards and paper tape; however, the output was displayed on printouts.

·     The first generation computers worked on binary-coded concept (i.e., language of 0-1). 

Examples: ENIAC, EDVAC, etc.

 

Second Generation

·   The period 1956 to 1963 is roughly considered as the period of Second Generation of Computers.

· The second generation computers were developed by using transistor technology.

·    In comparison to the first generation, the size of second generation was smaller.

·        In comparison to computers of the first generation, the computing time taken by the computers of the second generation was lesser.

Third Generation

·  The period 1963 to 1971 is roughly considered as the period of Third Generation of computers.

·     The third generation computers were developed by using the Integrated Circuit (IC) technology.

·   In comparison to the computers of the second generation, the size of the computers of the third generation was smaller.

·        In comparison to the computers of the second generation, the computing time taken by the computers of the third generation was lesser.

·    The third generation computer consumed less power and also generated less heat.

·       The maintenance cost of the computers in the third generation was also low.

·     The computer system of the computers of the third generation was easier for commercial use.

 

Fourth Generation

·    The period 1972 to 2010 is roughly considered as the fourth generation of computers.

·   The fourth generation computers were developed by using microprocessor technology.

·      By coming to fourth generation, computer became very small in size, it became portable.

·        The machine of fourth generation started generating very low amount of heat.

·        It is much faster and accuracy became more reliable.

·  The production cost reduced to very low in comparison to the previous generation.

·        It became available for the common people as well.

Fifth Generation

·    The period 2010 to till date and beyond, roughly considered as the period of fifth generation of computers.

·    By the time, the computer generation was being categorized on the basis of hardware only, but the fifth generation technology also included software.

·     The computers of the fifth generation had high capability and large memory capacity.

·    Working with computers of this generation was fast and multiple tasks could be performed simultaneously.

·   Some of the popular advanced technologies of the fifth generation include Artificial intelligence, Quantum computation, Nanotechnology, Parallel processing, etc.

Input devices:

Input devices used in a computer.

·        Keyboard

·        Mouse

·        Light pen

·        Joystick

·        Scanner

·        Digitizer

·        trackball

·        Microphone

·        MCR

·        OCR

·        Bar coder

Keyboard

·    Keyboard is the most common and very popular input device which helps to input data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing additional functions.

·        Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.

	Keys & Description
1	Typing Keys These keys include the letter keys (A-Z) and digit keys (09) which generally give the same layout as that of typewriters.
2	Numeric Keypad It is used to enter the numeric data or cursor movement. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machines and calculators.
3	Function Keys The twelve function keys are present on the keyboard which are arranged in a row at the top of the keyboard. Each function key has a unique meaning and is used for some specific purpose.
4	Control keys These keys provide cursor and screen control. It includes four directional arrow keys. Control keys also include Home, End, Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc).
5	Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.

Mouse

·        Mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU when the mouse buttons are pressed.

·      Generally, it has two buttons called the left and the right button and a wheel is present between the buttons. A mouse can be used to control the position of the cursor on the screen, but it cannot be used to enter text into the computer.

Advantages

• Easy to use          
• Not very expensive
• Moves the cursor faster than the arrow keys of the keyboard.

 

Joystick

·        Joystick is also a pointing device, which is used to move the cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. The joystick can be moved in all four directions.

·      The function of the joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.

 

 

Light Pen

·     Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube.

·   When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU.

Track Ball

·   Track ball is an input device that is mostly used in notebook or laptop  computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved.

·   Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes in various shapes like a ball, a button, or a square.

 

 Scanner

·      Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation.

·   Scanner captures images from the source which are then converted into a digital form that can be stored on the disk. These images can be edited before they are printed.

Digitizer

·  Digitizer is an input device which converts analog information into digital form. Digitizer can convert a signal from the television or camera into a series of numbers that could be stored in a computer. They can be used by the computer to create a picture of whatever the camera had been pointed at.

·     Digitizer is also known as Tablet or Graphics Tablet as it converts graphics and pictorial data into binary inputs. A graphic tablet as digitizer is used for fine works of drawing and image manipulation applications.

 

Microphone

·    Microphone is an input device to input sound that is then stored in a digital form. The microphone is used for various applications such as adding sound to a multimedia presentation or for mixing music.

 Magnetic Ink Card Reader (MICR)

·   MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable.

·  This reading process is called Magnetic Ink Character Recognition (MICR). The main advantages of MICR are that it is fast and less error prone.

 

Optical Character Reader (OCR)

·     OCR is an input device used to read a printed text.

·  OCR scans the text optically, character by character, converts them into a machine readable code, and stores the text on the system memory.

 

Bar Code Readers

·   Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner.

·   Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer that the bar code reader is connected to.

 

 Optical Mark Reader (OMR)

 

·   OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.It is specially used for checking the answer sheets of examinations having multiple choice questions.

Output devices :

Output devices used in a computer.

• Monitors
• Graphic Plotter
• Printer

Monitors

·     Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer.

·      It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.

ü  Cathode-Ray Tube (CRT)

ü  Flat-Panel Display

Cathode-Ray Tube (CRT) Monitor

·     The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution.

·     It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

·      A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

There are some disadvantages of CRT −

ü  Large in Size

ü  High power consumption

Flat-Panel Display Monitor

·   The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists.

·    Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

The flat-panel display is divided into two categories −

ü  Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).

ü  Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).

Printers

Printer is an output device, which is used to print information on paper.

There are two types of printers −

ü  Impact Printers

ü  Non-Impact Printers

Impact Printers

Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.

Characteristics of Impact Printers are the following −

• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image

These printers are of two types −

ü  Character printers

ü  Line printers

Character Printers

Character printers are the printers which print one character at a time.

These are further divided into two types:

• Dot Matrix Printer(DMP)
• Daisy Wheel

Dot Matrix Printer

·       In the market, one of the most popular printers is Dot Matrix Printer.

·   These printers are popular because of their ease of printing and economical price.

·    Each character printed is in the form of pattern of dots and head consists of Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form acharacter which is why it is called Dot Matrix Printer.

Advantages

• Inexpensive
• Widely Used
• Other language characters can be printed

Disadvantages

• Slow Speed
• Poor Quality

Daisy Wheel

·      Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer.

·     These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality.

Advantages

• More reliable than DMP
• Better quality
• Fonts of character can be easily changed

Disadvantages

• Slower than DMP
• Noisy
• More expensive than DMP

Line Printers

Line printers are the printers which print one line at a time.

These are of two types −

ü  Drum Printer

ü  Chain Printer

Drum Printer

·      This printer is like a drum in shape hence it is called drum printer.

·       The surface of the drum is divided into a number of tracks.

·   Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track.

·     Different character sets available in the market are 48 character set, 64 and 96 characters set.

·        One rotation of drum prints one line.

·        Drum printers are fast in speed and can print 300 to 2000 lines per minute.

Advantages

• Very high speed

Disadvantages

• Very expensive
• Characters fonts cannot be changed

Chain Printer

In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.

Advantages

• Character fonts can easily be changed.
• Different languages can be used with the same printer.

Disadvantages

• Noisy

Non-impact Printers

Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

These printers are of two types −

ü  Laser Printers

ü  Inkjet Printers

Characteristics of Non-impact Printers

• Faster than impact printers
• They are not noisy
• High quality
• Supports many fonts and different character size

Laser Printers

·      These are non-impact page printers.

·      They use laser lights to produce the dots needed to form the characters to be printed on a page.

Advantages

• Very high speed
• Very high quality output
• Good graphics quality
• Supports many fonts and different character size

Disadvantages

• Expensive
• Cannot be used to produce multiple copies of a document in a single printing

Inkjet Printers

·   Inkjet printers are non-impact character printers based on a relatively new technology.

·        They print characters by spraying small drops of ink onto paper.

·        Inkjet printers produce high quality output with presentable features.

·    They make less noise because no hammering is done and these have many styles of printing modes available.

·   Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.

Advantages

• High quality printing
• More reliable

Disadvantages

• Expensive as the cost per page is high
• Slow as compared to laser printer

Classifications of digital computer system:             

Computers can be broadly classified by their speed and computing power.

S.No.	Type	Specifications
1	PC (Personal Computer)	It is a single user computer system having moderately powerful microprocessor
2	Workstation	It is also a single user computer system, similar to personal computer however has a more powerful microprocessor.
3	Mini Computer	It is a multi-user computer system, capable of supporting hundreds of users simultaneously.
4	Main Frame	It is a multi-user computer system, capable of supporting hundreds of users simultaneously. Software technology is different from minicomputer.
5	Supercomputer	It is an extremely fast computer, which can execute hundreds of millions of instructions per second.

PC (Personal Computer)

·    A PC can be defined as a small, relatively inexpensive computer designed for an individual user.

·     PCs are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Businesses use personal computers for word processing, accounting, desktop publishing, and for running spreadsheet and database management applications.

·    At home, the most popular use for personal computers is playing games and surfing the Internet.

·   Although personal computers are designed as single-user systems, these systems are normally linked together to form a network. In terms of power, now-a-days high-end models of the Macintosh and PC offer the same computing power and graphics capability as low-end workstations by Sun Microsystems, Hewlett-Packard, and Dell.

Workstation

· Workstation is a computer used for engineering applications (CAD/CAM), desktop publishing, software development, and other such types of applications which require a moderate amount of computing power and relatively high quality graphics capabilities.

·  Workstations generally come with a large, high-resolution graphics screen, large amount of RAM, inbuilt network support, and a graphical user interface.

·    Most workstations also have mass storage device such as a disk drive, but a special type of workstation, called diskless workstation, comes without a disk drive.

·       Common operating systems for workstations are UNIX and Windows NT. Like PC, workstations are also single-user computers like PC but are typically linked together to form a local-area network, although they can also be used as stand-alone systems.

Minicomputer

·        It is a midsize multi-processing system capable of supporting up to 250 users simultaneously.

• Minicomputers (colloquially, minis) are a class of multi-user computers that lie in the middle range of the computing spectrum, in between the smallest computers and the largest single-user systems (microcomputers or personal computers).
• The term super minicomputer or super mini was used to distinguish more powerful minicomputers that approached mainframes in capability.
• Super minis (such as the DEC VAX or Data General Eclipse MV/8000) were usually 32-bit at a time when most minicomputers (such as the PDP-11 or Data General Eclipse or IBM Series/1) were 16-bit.

Mainframe

·   Mainframe is very large in size and is an expensive computer capable of supporting hundreds or even thousands of users simultaneously.

·   Mainframe executes many programs concurrently and supports many simultaneous execution of programs.

Supercomputer

· Supercomputers are one of the fastest computers currently available.

·  Supercomputers are very expensive and are employed for specialized applications that require immense amount of mathematical calculations (number crunching).