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CCC Study Material in English Introduction to Computer


CCC Study Material in English Introduction to Computer:- Course on Computer Concept (CCC) Based on NIELIT (DOEACC) Latest Syllabus, CCC important Study Material in English 2019 Study Guide, CCC Study Material With Model Practice Sets Available this Post, Please Read This Post CCC Study Material Online PDF (Download) Full Course.

Introduction to Computer (DOEACC CCC Study Material)

A computer is an electronic device that manipulates information or data according to the set of instructions called programs. It has the ability to store, retrieve and process data. A computer is used to type documents, send E-mails and browse the Internet. It is also used to handle accounting, database management, presentations, and games and so on. The term ‘computer’ is derived from the Latin word ‘computer’, which means ‘to calculate’.

What is Computer?

A computer is an electronic machine that accepts data
from the user, processes the data by performing
calculations and operations on it and generates the desired
output as a result.

Charles Babbage is called the father of computer’.
Generally, computer is the combination of hardware
and software, which Converts data into information.
Some terms used in computer terminology are
described below:



Data Unprocessed raw facts and figures, like Computer numbers, text on pieces of paper, are known as data.

Processing It is the sequence of actions taken on data to convert it into information.

Information When data is processed, organized, structured or presented in a given context so as to be useful, then it is called information.

Instruction It is a command given to a computer in the computer language by the user.

Program It is a set of instructions given to a computer in order to perform some task.

History of Computer (CCC Study Material)

Computers were preceded by many devices developed by mankind for their computing requirement Flowerier; many centuries elapsed before technology was adequately advanced to develop computers. The key development that took place ll the first computer w develoP are as follows:

Characteristics of Computer (NIELIT CCC Study Material)

Most of the world’s infrastructure  runs on computers and computers have profoundly changed our lives, for the better improvement. Let us discuss some of the characteristics of a computer:

(i) Speed The computer can process data very fast at the rate of millions of instructions per second.

(ii) Accuracy Computer provides a high degree of accuracy. Computer responds to the user as per the input instructions.

(iii) Storage Capacity Computers are capable to store huge amount of data, which depends on the capacity of hard disk.

(iv) Versatility Computers can do different types of work simultaneously. They can perform multiple tasks at a same time.

(v) Plug and Play Computers has the ability to automatically configure a new hardware and software component.

(vi) Diligency Unlike human beings, a computer is free from monotony, tiredness, lack of concentration, etc, and can work for hours without creating any errors.

(vii) Secrecy Leakage of information is reduced by creating login system with password protection e.g. ATM counter, E-mail, etc.

(viii) Reliability Computer are more reliable than human beings. Computers always produce exact results. The possibility of errors occur only if the input is wrong, i.e. the computers never make mistakes of their own accord.

Applications of Computer
Now-a-days computers have been employed in almost all the aspects of professional and personal life. Some of the areas where computers being used are given below:

Application of Computer

Application of Computer

(i) Education

Computers have proved to be excellent teachers. Educational institutes are using computers in many ways like tele-education, virtual classroom, online classes, etc.

(ii) Scientific Research

Scientists have long been users of it. A new adventure among scientists is the idea of a collaboratory (an Internet based collaborative laboratory) in which researchers from all over the world can work easily together even at a distance.
(iii) Business Application

Computers play a vital role in business. To keep records of employees, sold product information and available resource is now easy.
(iv) Recreation and Entertainment

Our entertainment and pleasure time have also been affected by computerization.

(v) Government

Various departments of the government use computer for their planning, control and law enforcement activities.

(vi) Health

Computer plays a very crucial role in this area. Activities like scanning, X-ray, tele-medicine, patient monitoring, patient records, diagnosis, etc. are performed with the help of computers.

(vii) Multimedia

Multimedia is the field concerned with the computer controlled integration of text, graphics, drawings, animation, audio and any other media, where each type of information can be represented, stored, transmitted and processed digitally.

(viii) Banks

Computers can be used in the banks to keep the records of customer’s accounts. Computers enhance customer services like checking account status, transferring money, etc.

Limitations of Computer
No learning power Computers have no learning power. Every time you perform same task, you have to give full instruction to the computers what to do and how to do it. Computers do not remember previous work.

(ii) No Decision Making Computers do not have decision making power like human being. Computers can not take decision without presence of instruction.

(iii) No Self Interference

With the help of computers, you can do almost all the work, but computers do not have interference of its own.

(iv) Interaction is Needed

Every time computers need a interaction. Users interact to computers to perform a task. If there is no interaction, computers can not do anything.

Classification of Computer (CCC STudy Material 2019)

Computers are mainly classified based on their different size and shapes.

classification of computer

classification of computer

Based on Size

On the basis of size, computers are categorized as follows:

Micro Computer

These are the least powerful, yet the most widely used and fastest growing type of computers and are also called portable computers.

Some types of micro computer are given below:

(i) Desktop Computer or Personal Computer (PC) These computers are small and relatively inexpensive computers. These computers are based on the microprocessor technology (Integrated Circuit).

(ii) Notebook These computers (also known as ultra book or laptop) are lightweight and fit into most briefcases. First laptop was developed by Alan Kay. Laptops consume less power than desktops and they include a rechargeable battery.

(iii) Handhelcl Computers or Palmtops These computer are the smallest and are designed to fit into the palm. So, these computers are also known as Palmtop/PDA.

(iv) Tablet Computer These computers have key features of the notebook computer, but it can accept input from a pen instead of the keyboard or mouse.

Mini Computer

These computers are smaller in size and faster than mainframe computers. Initially, the mini-computers were designed to carry out some specific tasks, like engineering and Computer Aided Design (CAD) calculations. They are used as central computer, which is called as server.

Mainframe Computer

These are the computers having large internal memory storage and comprehensive range of software. These computers are bigger in size comparatively to mini computers but smaller than supercomputers. Mainframe computer serves as a backbone for the entire business world. Mainframe computers are IBM-370, IBM-S/390, UNIVAC- 1110.

Super Computer

These are the fastest and the most expensive machines. The speed of supercomputers are measured in FLOPS (Floating Point Operations Per Second).

Supercomputers are used for highly calculation intensive tasks, such as weather forecasting, nuclear research, military agencies and scientific research laboratories. “PARAM was the first supercomputer of India introduced by CDAC in 1991”.

Based on Work

On the basis of work, computers are categorized as follows:

Analog Computer

An analog computer that uses the changeable aspect such as electric, mechanical quantities to solve the problem. These computers carry out arithmetic and logical operations by manipulating and processing of data, e.g. speedometers, seismograph, etc.

Digital Computer

These computers work by calculating the binaiy digits. A digital computer not only performs mathematical problems, but also combines the bytes to produce desired graphics, sounds, e.g. desktop (PC).

Hybrid Computer

These computers are the combination of analog and digital computers. Machines used in hospitals like ECG and DIALYSIS are the commonly used hybrid computer. These computers Contain special equipment to convert analog voltage to digital voltages and vice-versa.

Based on Purpose

On the basis of purpose, computers are categorized as follows:

General Purpose Computer

These computers are used to solve variety of problems by changing the program or instructions, e.g. to make small database calculations, accounting, etc.

Special Purpose Computer

These computers are used to solve a single and dedicated type of problem, e.g. automatic aircraft landing, multimedia computer, etc.

Components of a Computer

A general purpose computer has three main components:

(i) Input/Output Unit

(ii) Central Processing Unit (CPU)

(iii) Memory Unit

Input / Output Unit

Input / Output devices are required for user to communicate with the computer. Input devices bring data INTO the computer system and output devices bring data OUT from a computer system.
These I/O devices are also known as peripheral devices like keyboard, mouse, printer, etc.

Components of a Computer

Components of a Computer


The Central Processing Unit (CPU) is the part of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical and input/output operations of the system.
The CPU is also known as the brain of the computer. The speed of CPU depends upon the type of microprocessor used and it is measured in Mega Hertz (MHz).


The microprocessor is fabricated on a single IC (Integrated circuit). IC is a piece of silicon,
composed by thousands of transistors.

The first chip, Intel 4004, made by Intel in 1971 by scientist Ted Hoff and engineer Frederica Faggin.
Some of the popular microprocessors are i5. i3, Core 2 Dual Intel, Dual Core, Pentium IV, etc.

Two typical components of a CPU are the Arithmetic Logic Unit (ALU) and the Control Unit (CU):

Arithmetic Logic Unit

In computing, an Arithmetic Logic Unit (ALU) is a digital circuit that performs arithmetic and logical Operations. The ALU is a fundamental building block of the central processing unit of a computer.
An ALU loads data from input registers and control unit tells the ALU that which operation is to be performed on that data and then the ALU stores its result into an output register.

Most ALUs can perform the following operations:

(1) Logical operations (AND, NOT, OR, XOR)

(ii) Arithmetic operations (addition, subtraction, multiplication and division).

(iii) Bit-shifting operations (shifting or rotating a word by a specified number of bits to the left or right, with or without sign extension).

(iv) Comparison operations (=, <, <=, >, >=)

Control Unit

The control unit coordinates the input and output devices of a computer system. It fetches the instructions which are given in the form of microp rograms. It directs the operation of the other units by providing timing and control signals.

In general, a control unit is a central part of the machinery that controls its operation and entire processing.

e.g. in the automobile industry, the control unit helps to maintain various functions of a motor vehicle.
The control unit is the circuit that controls the flow of data through the processor and coordinates the activities of the other units within it. Control unit acts like human nerves system, which does not process data but behaves as a central unit for other data manipulating components.


It is the internal part of CPU. These are used to store intermediate results obtained during the execution of  instruction.

Memory Unit

This unit is responsible to store programs or data on a temporary or permanent basis. It has primary memory (main memory) and secondary memory (auxiliary memory). The input data which is to be processed is brought into main memory before processing.

The needed instruction for processing and any kind of intermediate results are also stored in primary memory. Together with these, the final output is also stored in primary memory before transferring it to the output unit. Another kind of memory is referred as secondary memory of a computer system. This unit is used to permanently store data, programs and output. This unit does not deal directly with CPU.

Input Devices

An input device is a hardware device that sends data intO the computer system. These devices are used to input (or enter) data and instructions into the computer system. All instructions are accepted by the CPU through electrical pulses from various kinds of input devices.

Some of the input devices are explained as follows:


It is the most commonly used input device which uses an arrangement of buttons and keys to. Both data and program, can be entered into the computer through the keyboard. It is an essential device for interactive processing because the user can easily issue commands to receive the data response immediately on the computer screen.



Types of Keys on Keyboard

(i) Alphanumeric keys All of the letters and numbers on the keyboard are A-Z and 0-9.

(ii) Punctuation keys Such as comma, period, semicolon, brackets, parenthesis and so on.

(iii) Special keys Such as Control keys, Arrow keys, Caps lock key, Delete key, Alt key, Shift key etc.

(iv) Function keys Keys labeled Fl to F12.

These keys have different meaning depends on running program.

Pointing Devices

A pointing device is used to communicate with the computer by pointing to the locations on the monitor. It can also be used for:

  • sending command signals to the computer.
  • selecting items on the screen.
  • selecting commands from commands menu.
  • drawing graphics, sketches, etc.

Some commonly used pointing device are mouse, trackball, joystick, lightpen, graphics tablet, touch screen and touch pad.

(i) Mouse

The mouse is a pointing device that allows to control the movement of pointer (also known as mouse pointer) on screen. Mouse performs various functions by detecting two-dimensional motion relatively to its supporting surface. A mouse can be of different types like wired, I wireless mouse, optical mouse, mechanical mouse etc. Generally a mouse have two buttons — a right button and left button.



Mouse also include a scroll wheel between the buttons to scroll down the application window and their contents also.

Different types of mouse are:

(a) Mechanical Mouse In this type of mouse, movement of a cursor on the screen is — relative to the movement of the ball available at the bottom of the mouse.

(b) Optical Mouse It uses a Light EmItting Diode(LED) and Photodiodes to detect movement.

(c) Laser Mouse It uses Infrared Laser Diode instead of a normal LED.

(d) Wireless Mouse It communicates with the computer via Radio waves (often using Bluetooth hardware and software) so that a cord is not needed (but such mouse needs internal batteries). A mouse also includes one or more buttons (and possibly a scroll wheel) to allow users to interact with the GUI.


(ii) Joystick

The joystick is also a pointing device like the mouse, which consists of a stick that pivots on a spherical ball on its base. A joystick is similar to a mouse excepts that the moment of cursor on screen stops working as soon as user stop moving the mouse. But with a joystick, the pointer continuous moving in the previously pointing direction. Commonly, joysticks are used for playing computer games like flight simulators but occasionally used for CAD/CAM systems and other applications.



Some joysticks also have a third degree of freedom i.e. the stick can be twisted in clockwise or anti-clockwise direction.

(iii) Light Pen

A light pen is a pointing device shaped like a pen and is connected to a Visual Display Unit

Light Pen

Light Pen

The tip of the light pen contains a light- sensitive element which, when placed against the screen, detects the light from the screen enabling the computer to identify the location of the tip of pen on screen.

(iv) Graphics Tablet

A graphics tablet (or digitizers, digitising tablet, tough tablets or simply tablet) is an input device that consists of an electronic writing area and a special pen that works with it. It allows artists to create hand-made images and graphical images with motion and action, similar to the way a person draws images with pencil and paper.

Graphics Tablet

Graphics Tablet

The pen of the graphics tablet is pressure sensitive, so pressing harder or softer can result in brush strokes of different width.

(vi) Touchpad (Track pad)

When user draws anything on the tablet with the special pen, the drawing appears on the screen.

The tablet and pen can also be used like a mouse to move the cursor and click. Graphics tablet may also be used to capture data or handwritten signatures.

(v) Touch Screen

It is an electronic visual display that can detect the presence and location of a touch within the display area. The term touch screen \Touch scre generally refers to touching the display of the device with a finger or hand. The touch screen sends a signal to the computer. This signal gives the location on the screen, which has been touched. Touch screen is quick and simple to use. Generally, smart phones have a high-resolution capacitive touch screen. There are different types of touch screens available with electronic devices like capacitive touch screen, resistive touch screen and gorilla glass touch screen, etc.

Touch Screen

Touch ScreenTouch screen is pressure sensitive and activated by finger or stylus. Touch screen works as:

  • Touch! Sensor It is a clear glass panel with a touch responsive surface.
  • Controller A small PC card that translates information that PC can understand.
  • Software Driver It allows to work with Existing software.

(vi) Touchpad Trackball

It is a specialised surface that can translate the motion and position of a user’s finger to a relative position on the screen. This is a common feature of laptop computers and also used as a substitute of a computer mouse, where disk space is scarce. The sensors of touchpad only react through fingertip and not a pencil or other object.

Touchpad Trackball

Touchpad Trackball

There are usually two buttons next to the touchpad which works as left and right button of the mouse.

(vii) Trackball

It is designed for computers; generally serves as mouse replace ment. It is primarily used to move the cursor on the screen. The trackball has a ball on its top. Trackball can be rolled with fingers and the internal rollers sense the motion, which is transmitted to the computer. Trackballs are common on CAD workstations and sometimes seen on Computerized special purpose work stations, such as the radar consoles in an air-traffic control room or sonar equipment on a ship or submarine.




It is a device that allows a user to take an image or text – / and convert it into a digital file, allowing the computer to
read or display the scanned Scanner object. Scanners can be used for storing the documents in their original form that can be modified and manipulated later on. It is mainly used to convert a scanned document in a digital format.



Scanners come in a variety of sizes from hand-held models to desktop models as discussed below:

(i) Hand-held Scanners They are very small which can be held in a hand. These are less expensive and less wide. Hence, in order to scan a single page image, multiple passes are required. But their handliness is a major advantage of hand-held scanner.

(ii) Flatbed Scanners They are large and more expensive scanners that creates higher quality images. These scanners have a flat surface on which the printed image to be scanned, is placed. (Similar to the way a page is placed on a photocopier). Flatbed scanners can scan a page in a single pass.

(iii) Drum Scanners They are medium size scanners with a rolling drum. The sheet is fed through the scanners so that the drum rolls over the entire sheet to be scanned (Just as the sheets are fed in a fax machine).


(Magnetic Ink Character Recognition)

It is a character recognition technology which is primarily used by the banking industry to facilitate the processing of cheques. This technology allows the computers to read information (such as account numbers) on printed documents. Characters are printed in special typefaces with a magnetic ink (that contains Iron Oxide).

MICR can read up to 2400 documents/mm. The MICR coding system contains 14 characters (four special symbols and 10 decimal digits). So, it can recognize these 14 characters only. The type font E- 13 B, a standard typographical style, is used to print the characters or identification marks.

Format of a Cheque

Format of a ChequeOCR
(Optical Character Recognition)
It is used to translate scanned images of handwritten, type-written, printed text or special type font printed on conventional paper with conventional ink into machine- encoded text.

Functioningof an OCR

Functioningof an OCR

It is widely used to convert books and documents into electronic files, to computerize a record-keeping system in an office or to publish the text on a website.

An optical reader uses photoelectric devices to scan the characters being read and convert the reflected light patterns of the data into binary data suitable for computer input.

Type font for OCR

Type font for OCR

The normal speed of an OCR is 1500 to 3000 characters per second.

The technology is being developed for greater accurate recognition and is also known as Intelligent Character Recognition (ICR).

OMR (Optical Mark Reader)

It is used to capture human marked data from document form such as surveys and tests.

One of the most familiar applications of optical mark reader is the checking of optical answer sheets in multiple choice questions:

It uses high intensity to read the marks or symbols. Optical mark reader

Optical Mark Reader

Optical Mark Reader

Barcode Reader

It is an input device used for reading printed bar codes (Universal Product Code) available on product to be sold. A bar code reader emits a beam of light, which reflects off the bar code image.
A light sensitive detector in the barcode reader identifies the bar code image by recognising special bars at both the ends of the image.

Once code is identified, it is converted into a numeric code. A perfect example of a barcode reader is its use in a super market where barcode scanner reads the price of a product.
Software like Wasp, Barcode Pro are used for scanning and printing barcodes.



A barcode is a machine readable representation of information in the form of stripes of dark and light ink.

Microphone (Mic)

We can send sound to the computer through a special manual input device called microphone or mic. A mic converts the received sound into computer’s format, which is called Digitized Sound or Digital Audio. To convert a voice into digital form, an additional hardware is always needed which is known as Sound Card.

Sound is used most often in multimedia, where user can make his/her presentation more attractive using recorded narration, music or sound effects.

A microphone can be attached to a computer to record sound. Now-a-days, microphones are also being used with speech recognition software.

Microphone (Mic)

Microphone (Mic)

This means that you do not have to type the document, rather just have to speak and the spoken words appear in your document.

Web Camera (Webcam)

Webcam is a digital camera attached to computers and can be used for video conferencing or online chatting, etc. It is a video capturing device. Webcams are able to capture full motion videos as well. A webcam connected to a computer allows the user to view either a still picture or motion video of a user or other object.
Now-a-days, webcams are either embedded into the display with laptops or connected via USB or fIrewire port or Wi-Fi to the computer system. After connecting webcam to a computer, you need to install required software or drivers.

Web Camera

Web Camera

Digital Camera (Digicam)

It is a device that stores the pictures or videos in an electronic format instead of film. There are several features that makes digital camera a popular choice, when compared to film cameras. Most enjoyable feature is the LCD display on the digital camera. This display allows users to view and save photos or video after the picture or video has been taken, that means, if you take a picture and don’t like the results, you can delete it, or if you like the picture, you can save it and easily show it to other people.

Digital Camera

Digital CameraBiometric Sensor

It is a device which recognizes physical or behavioral traits of the individual. Biometric sensors are mainly used marking Biometric attendance of employees! Sensor studentsin organizations / institutions. Biometric sensors are working with accuracy, so these can be widely used in security purpose.

Biometric Sensor

Biometric Sensor

Output Devices

An output device is a part of computer hardware equipment, used to communicate the results of data processing which are carried out by an information processing system (such as a computer), to the outside world. Output devices carry the results of various operations performed by the user. Some of the devices, which are used to display the processed result or output are as follows:


A monitor (called a visual display unit) is an electronic visual device used to display the output. The rectangular area of the monitor, its refresh rate and dot pitch, all directly affect the resolution of the display.

Resolution refers to the clarity of screen and measured by the number of individual tiny coloured dots (knows as pixels), scattered on the screen. Resolution indicates the number of dots per inch. The smaller the dot pitch is, the better the resolution will be.

Types of Monitors

The popular type of monitors are as follows:

(i) CRT (Cathode Ray Tube) The CRT works in the same way as a television. It contains an electron gun at the back of the glass tube. This gun fires electrons in a group of phosphor dots, which is coated inside the screen. When the electrons strike the phosphor dots they glow to give the colors

CRT Monitor

CRT Monitor

(ii) LCD (Liquid Crystal Display) These screens are used in laptops and notebook sized PCs. A special type of liquid is sandwiched between two plates. It is a thin, flat and light weight screen made up of any number of colors or
mono-chrome pixels arranged in front of a light source. Some of the major features of LCD monitors are:



  • Long life
  • Light weight
  • Better screen privacy
  • Less eyestrain
  • Reduced radiation

(iii) LED (Liquid/Light Emitting Diode)

LED is an electronic device that emits light when electrical current is passed through it. LEDs usually produces red light, but today’s LEDs can produce RGB (Red, Green and  Blue) light and white light as well.

LED Monitor

LED Monitor

(iv) 3-D Monitor  

Impact printer’s varieties includes: 3-D Monitor is a television that conveys depth perception to the viewer 3-D describes an image that provides the perception of length. When 3-D images are made interactive, user feels involved with the scene and this experience is called virtual reality.

3D Monitor

3D MonitorTFT (Thin Film Transistor) —i

TFT and Active-Matrix LCD (AMLCD) is a Liquid Crystal Display (LCD). With active-matrix displays, each pixel is controlled by one to four transistors that can make the screen faster, brighter, more colourful than passive-matrix and capable of being viewed at different angles. Because of this improved technology, active-matrix screens are often more expensive but have better quality than a passive-matrix display.


A printer is an output device, which produces a hard copy of documents that are stored in an electronic form on physical print media such as paper or transparencies. So printers are the primary output devices used to prepare permanent documents. The speed of a printer is normally rated either by Pages Per Minute (PPM) or by Characters Per Second (CPS).

Printers can be classified into two broad categories

(i) Impact Printers

(ii) Non-Impact Printers.

(i) Impact Printers

Impact printers rely on a forcible impact to transfer ink to the print media, similar to the action of a typewriter. There is a mechanical contact between the paper and the print head.

(a) Line Printer These are impact shaped character printers which capable of printing an entire line at one instead of one or more character at a time. Print quality of line printer is not high.

Line Printer

Line Printer

(b) Drum printer It is an old line printer technology that is used to formed character images around a Drum printer
cyhndncal drum as its printing mechanism. When the desired character for the selected position rotated around the hammer line, the hammer hit the paper from behind and pushed it into the ribbon and onto the character.

Drum Printer

Drum Printer

(c) Daisy wheel printer It can print one character at a time. In daisy wheel printer, round disk extends a portion of the wheel making contact with ink ribbon that makes contact with paper for creating the character. This procedure is repeated for each key when it is pressed. These printers are fitted with unchangeable print heads called daisy wheels. To print each character, the wheel is rotated and the appropriate stoke struck against an inked ribbon. Daisy wheel printers cannot produce high quality print graphics. The speed of daisy wheel printer is about 100 cps.

(d) Dot matrix printer The term dot matrix refers to the process of placing dots to form an image. It uses print heads to shoot ink or strike an ink ribbon to place hundreds to thousands of little dots to form text or images. It prints one character at a time. The speed of dot matrix printer lies between 200 to 600 cps.
The quality of the image is determined by the dots per inch. These printers are slow, noisy and are not commonly used for personal computers. They can print multi-layer forms, which neither inkjet nor laser printers can print. It can print special characters and graphics. Dot matrix printer do not have fixed character fonts.

(ii) Non-impact Printers

Non-impact printers are much quieter than impact printers as their printing heads do not strike the paper. Most non-impact printers produce dot-matrix patterns. There is no mechanical contact between the paper and the print head. These printers are comparatively faster and produce high quality output. They can be used for printing text and graphics both in black and white and colored.

The main types of non-impact printers are as follows:

(a) Electromagnetic printer Electrographic or electro- photographic printers are very fast printers and they fall under the category of page printers. They can produce documents at a speed of over 20000 lines per minute i.e. more than 250 pages per minute. The electrographic technology has developed from the paper copier technology.

(b) Thermal printer Thermal printer paper tends to darken over time due to exposure of sunlight or heat. The standard of print produced is poor. Thermal printers are widely used in battery powered equipment such as portable calculators.

(c) Electrostatic printer Electrostatic printers are generally used for large format printing. They are favored by large printing shops because of their ability to print fast, making

(d) Laser Printer In laser printer, the method of printing is based on principle of electro photography
and use a beam of  laser light as a photocopy machine. The powered ink (i.e. toner) is transferred to paper to form a text/image pattern and then fixed by heat or pressure. When used to print bulk of papers, the laser printer produces the cheapest cost per printout.

Laser Printer

Laser Printer

(e) Inkjet Printer An inkjet printer fires extremely small droplets of ink onto the paper to create —t impression of text or image. The print head of inkjet printer inkjet printers, known as print cartridge, contains tiny nozzles (50 or more) through which different colored inks can be sprayed onto the paper to form the characters or graphic images. Color inkjet printers provide an inexpensive way to print fully colored documents.

Inkjet Printer

Inkjet Printer


Its a output device similar to a printer that uses a pen, pencil, marker or other writingtoolto make a design. Plotters are generally used to generate the map of otter building and shopping malls. A plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as Computer Aided Design (CAD) and other print jobs. Though they have generally been replaced with wide-format conventional printers



There are two basic types of plotters those that use pens and those that do not. Drum plotters and flatbed plotters use pens but electrostatic plotters do not use the same.

(i) Drum plotter A drum plotter contains a long cylinder and a pen carriage. The output paper is placed over the drum. The pen is mounted horizontally on the carriage. Both the pen and drum move under the computer’s control to produce the desired drawing.

(ii) Flatbed plotter A flatbed plotter consists of a stationary horizontal flat surface on which paper or any other medium is fixed. The pen is mounted on a carriage that can move along the horizontal and vertical axis.

(iii) Electrostatic plotter it mark paper with electrostatic charges and run it through a developing system to create an image. They produce high-quality images and are used by graphic and commercial artists.


Speaker is an output device that receive the sound in the form of electric current from the sound card and convert it into sound format. Speakers are used for listening to music.



Computer speakers (multimedia speakers) are the speakers which are attached internally or externally to a computer system.


Headphones are a pair of small loudspeakers or less commonly a single speaker, held close to a user’s ears and connected to a signal source such as an audio amplifier, radio, CD player or portable media player.



They are also known as stereo phones, headsets or cans.


it is an output device, which is used to project information from a computer onto a large screen, so it can be viewed by a large group of people simultaneously.

Projectors are widely used for classroom training or conference holes with a large audience. It provides a temporarY output display.

Speech Synthesizer

Speech synthesizer is used to produce sound from a text and can be implemented in software and hardware. A text to speech system convert normal language text into speech.

Computer Memory

The computer memory is one of the most important elements in a computer system. It is the internal or external storage area, which holds the data and instructions during processing in the form of binary numbers.
It also relates to many devices and components that are responsible for storing data and applications on a temporary or a permanent basis.

Computer memory can be classified into two

(i) Primary memory and

(ii) Secondary memory/Storage device.

Primary Memory

It is also known as Main Memory. It is the internal storage memory used by computer to hold data and instructions. The primary memory has limited storage capacity.

Primary memory holds the data and programs needed at that instant by CPU.

Primary memory is volatile in nature i.e. it requires constant power supply to motion the current information.

There are two types of Primary Memory:

(i) RAM

(ii) (ROM)


RAM stands for Random Access Memory. It is the internal memory that can be read from as well as written to. ‘‘h RAM memory is often associated with volatile types of memory. It can hold data only on temporary basis because it requires a continuous flow of electrical current.



If current is interrupted, data is lost, it is an integrated circuit that enables you to access the stored data in a random order constantly.

lie two main forms of RAM are:

(a) Static RAM It is also written as S RAM. It is a computer memory that requires a constant power flow in order to hold information. S RAM is more expensive and requires more power therefore it is commonly used in cache and video card memory. It is faster than DRAM.

(b) Dynamic RAM It is also written as DRAM. It stores information in a cell containing a capacitor and transistor, these cells must be refreshed with electric impulses in few milliseconds. This process allows memory to keep charge and hold the data as long as needed.

There are some enhanced versions of RAM, hich are as follows:

  1. a) EDORAM (Extended Data Output Random Access Memory)

(b) SDRAM (Synchronous Dynamic Random Access Memory)

c DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory)

(ii) ROM

In ROM (Read Only memory). memory, once stored main fixed, i.e. it can not changed. So, ROM can ROM
dv be read and used. Generally, it contains a set of start-up liructions, i.e. what to do when a computer is ued ON. The contents of ROM remain stored lcn if power is turned OFF. This memory is often coated with non-volatile types of memory. A DM cannot be altered once the chip has been .de.
DM is further sub divided into several types:



(a) PROM (Programmable Read Only Memory) It is a computer memory chip capable of being programmed after it has been created. But once the PROM has been programmed, the information written is permanent and cannot be erased or deleted.

(b) EPROM (Erasable Programmable Read Only Memory) It is a computer memory chip on which the written information can be changed by exposing to ultra voilet light. It is just like a small glass circle that expose the chip that can be re-programmed.

(c) EEPROM (Electrically Erasable Programmable Read Only Memory) It is a PROM that can be erased and reprogrammed using an electrical charge.

Cache Memory

Cache (pronounced cash) memory is extremely fast memory that is built into a computer’s central processing unit, or located nect to it on a separate chip. The Cpu uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed. As the microprocessor processes data, it first looks in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the time-consuming reading of data from larger memory. The advantage of cache memory is that if needed data is found in cache then the cu does not have to use the motherboard’s system bus for data transfer and thus processing gets fast.

Storage Devices/Secondary Memory

Secondary memory, also known as Secondary Storage or Auxiliary Memory, is the slower and cheaper form of memory. It is a permanent storage device.

CPU does not access the secondary memory directly. The content in it must first be copied into the RAM to be processed. Secondary memory is non-volatile in nature. i.e. the information does not get erased even when power is switched OFF and data will not be destructed until and unless the user erases it.

Secondary Memory devices include

Magnetic disks Optical discs Solid State

Fbppy Disk CD Pen/Hash Drive

Hard Disk Drive DVD ______

Magnetic Tape Blue-ray Disc

(i) Floppy Disk (Diskette)

A Floppy Disk Drive (FDD) is a computer disk drive that enables a user to save data on removable diskettes. This portable storage device is a rewritable media and can be reused a number of times. It is made of plastic with magnetic coating on it. It is round in shape and is covered by square plastic jacket.

Floppy disks are commonly used to move ifies between different computers. Although 8” disk drives made available in 1971 were the first real disk drives, the first widely used floppy disk drives were the 4”, 5 floppy disk drives, which were later
replaced with 3 floppy disk drives.

However, today these drives are being replaced with CD-R and other writeable disc drives and flash drives. MB. diameter-floppy has a capacity of 1.2 3 diamel. -floppy has a capacity of  1.44 MB.

(ii) Hard Disk Drive

A Hard Disk Drive (HDD) is a non-volatile, random access digital data storage device. It is a data storage device used for storing and retrieving digital information using rotating disks (platters) coated with magnetic material. All programs of a computer are installed in hard disk within a particular drive.

Hard Disk Drive

Hard Disk Drive

It consists of a spindle that hold non—magnetic flat circular disks, called platters, which hold the recorded data. Each platter requires two read/write heads, that is used to write and read the information from a platter. All the read/write heads are attached to a single access arm so that they cannot move independently.
The information is recorded in bands, each band of information is called a track. Each platter has the same number of tracks and a track location that cuts across all platters is called a cylinder. The tracks are divided into pie-shaped sections known as sectors.

(iii) Magnetic Tape

It is a medium of data storage, made up of a magnetic material. It is a storage medium on a large open reel or in a smaller cartridge or cassette (like a music cassette). It is used for those applications that are based on sequential data processing i.e. it is a sequential data access medium.

Due to this (sequential data access) nature, these tapes are not suitable for data files that need to be revised or updated often. They are generally used to store backup data or that type of data, which is not frequently used or to transfer data from one system to another.

(iv) Compact Disc (CD)

CD is an optical media that is used to store digital data.

The compact discs are relatively cheap storage devices.

Compact Disc (CD) are categorized into three main types:

(a) CD-ROM (Compact Disc-Read Only Memory) Data is recorded permanently on the surface of the optical disk through the use of laser.

The recorded content cannot be changed or erased by users. It is also called WORM (Write Once Read Many) disc. It is capable of storing large amounts of data—up to 1GB, although the most common storage capacity is 700 MB.
(b) CD-R (Computer Disc- Recordable) Data can be written on these discs only once. The data once stored in these discs cannot be erased.

(c) CD-RW (Compact Disc- Rewritable) It is an erasable disc. CD-RW is used to write data multiple times on a disc by the use of format feature.

(v) Digital Video Disc (DVD)
Digital Video Disc (DVD) is also known as Super Density (SD) Disc. A DVD is an optical disc storage media manufactured for the first time by Philips, Sony, Toshiba and Panasonic in 1995. DVDs offer higher storage capacity than compact discs while having the same dimensions.

Digital Video Disc

Depending upon the disk type, DVD can store several Gigabytes of data (4.7 GB-17.08 GB).
DVDs are primarily used to store music or movies and can be played back on your television or on the computer too. They are not rewritable media.

DVDs come in three varieties:

(i) DVD ROM (Digital Video Disc-Read only Memory)

(ii) DVD-R (DVD-Recordable)

(iii) DVD-RW (DVD-Rewritable)

(vi) Blu-ray Disc

Blu-ray Disc (official abbreviation BD) is an optical disc storage medium designed to recapture the data normally in DVD format. Blu-ray Discs Blue-ray disc contain 25 Gb (23.31 GB) per layer space. The name bin-ray disc refers to the blue laser used to read the disc, which allows information to be stored at a greater density.

Blu-ray Disc

Blu-ray Disc

Blu-ray can hold almost 5 times more data than a single layer DVD.

The variations in the formats are as follows:

(a) BD-ROM (Read only) for pre-recorded content

(b) BD-R (Recordable) for PC data storage

(c) BD-RW (Rewritable) for PC data storage

(d) BD-RE (Rewritable) for HDTV recording

(vii) Pen/Flash/Thumb Drive

A flash drive is a data
storage device that consists
of flash memory (USB
memory/key memory) with
an integrated, Universal
Bus (USB) interface. Pen Drive USB flash drives are typically removable, rewritable and physically much smaller than a floppy disk. A USB flash drive, data stick, thumb drive and a pen drive is a portable drive that is same as the size of your thumb that connects to the computer USB port.

Today, flash drives are available in various storage capacities as 256MB, 512MB, 1GB, 4GB, 16GB and 64 GB etc. Flash drives are widely used as an easy and small medium to transfer and store the information from the computers.

Pen Drive

Pen Drive

Basic Units of Measurement
When user use a RAM, ROM, Floppy disk or Hard disk, the data is measured using some units. In computer terminology, they are called Nibble, Bit, Byte. Kilobyte and Gigabyte etc.

Units of computer memory measurements

Bit (Binary digit) The smallest unit of data. It is either 0 or 1.

Nibble A group of 4 bits or half a byte.

Byte A group of 8 bits. A byte can represent 256 (28) distinct values,
such as the integers from 0 to 255. Each keyboard character is
represented through atleast 1 byte.

Kilobyte (KB) It is actually 210 bytes or 1 KB 1024 bytes.

Megabyte (MB) It is actually 220 bytes on MB=1024K8.

Gigabyte (GB) It is actually 2° bytes or 1 GB = 1024 MB.

Terabyte (TB) It is actually 2° bytes oil TB=1024GB.

Petabyte (PB) It is actually 2° bytes or 1 PB1024T8.

Exabyte (EB) It is actually 2 bytes on EB=.1024P8.

Zettabyte (ZB) It is actually 2° bytes on ZB=1024E8.

Yottabyte (YB) It is actually 2° bytes oil YB1024ZB.

BrontobYte It is actually 2° bytes or 1 Brontobyre = 1024 YB

Gebpbyte It is actually 2100 bytes or 1 Geopbyte = 1024 BrontobYte.

Geopbyte is the highest memory measurement unit.

Concept of Hardware and Software

A computer is a combination of hardware and software. These two work combinedly and make computer do for what it is instructed.


The term hardware refers to the physical components of a computer such as Keyboard Mouse, Monitor and Printer, including the digital circuitry. It is an integral part of a computer embedded in all modern day machines, automobiles, microwave ovens, compact disc players.


Software is a collection of computer programs, procedure and related data that provide the instructions for telling a computer what to do and how to do it. A software is a interface between user and computer. It is a set of instructions and programs that are used to give command to hardware. It is responsible for controlling, integrating and managing the hardware components of a computer system and for accomplishing specific tasks. Software can be divided into two major categories:

(1) System software

(ii) Application software

System Software

System software consists of several programs which are directly responsible for controlling, integrating and managing the individual hardware components of a computer system. It also provides the interface between the user and component of the computer. Some common examples of system software are operating system, device drivers and language translators.

(1) Operating System

It consists of programs which controls, coordinates arid supervises the activities of the various components of a computer system. Its function is to provide link between the computer hardware and the user. It performs all internal management functions (disk access, memory management task scheduling and user interfacing) and ensures systematic functioning of a computer system. It provides an environment to run the programs. e.g. MS-DOS, Windows XP/2000/98, Unix, Linux, etc.

IT he operating system performs the following functions:

(a) It makes sure that programs running at the same time do not interfere with

(b)  It is also responsible for security, ensuring that unauthorized users do not access the system.

(ii) Device Drivers

A software, which is written with the ejective of making a device functional when it is connected to the computer is called device driver.

It is a system software that acts like an Interface between the device and the user. Livery device, whether it is a printer, monitor, mouse or keyboard has a driver program associated with it for its proper functioning..

(iii) Language Translator

A language translator helps in converting programming languages to machine engage. The translated program is called dject code. There are three different kinds d language translators:

  1. a) Assembler It is used to convert the assembly language into machine language (i.e. in the form of 0 or 1). This language consists of mnemonic codes, which are difficult to learn and is machine dependent.
  2. Compiler It is used to convert the source code (written in high level language) into machine language. Compiler reads whole source code in a single run and traps the errors and informs to the programmer. For each high level language, the machine requires a separate compiler.

c Interpreter This program converts a high level language program into machine language by converting it line-by-line and inform to the user as an error occurs.

System Utilities

They are used to support, enhance, expand and secure existing programs and data in the computer system. System utility mainly consists of the following functions:

(i) Disk Compression

It increases the amount of information that can be stored on a hard disk by compressing all information stored on a hard disk.

(ii) Disk Fragmenters

It can be used to rearrange files and unused space on your hard disk.

(iii) Backup Utilities

It can make a copy of all information stored on a disk and restore either the entire disk or selected files.

(iv) Disk Cleaners

It is used to find files that have not been used for a long time. This utility also serves to increase the speed of a slow computer.

(v) Anti-virus

It is the utility, which is used to scan computer for viruses and prevent the computer system files from being corrupt. e.g. Norton, Quick heal, etc.

(vi) Clipboard manager

This utility program enhance clipboard capability of operating system.

Application Software

Application software is a computer software designed to help the user to perform singular or multiple tasks. It is a set of instructions or programs designed for specific uses or applications, that enable the user to interact with a computer. Application software are also called the end-user programs. There are two types of application software: