unit2

Unit 02: Basics of Computer

Computer Literacy 10

In this unit we present an overview of the basic design of a computer system: how the

different parts of a computer system are organized and various operations performed

to perform a specific task. You would have observed that instructions have to be fed

into the computer in a systematic order to perform a specific task. Computer

components are divided into two major categories, namely, hardware and software. In

this unit we will discuss about hardware, i.e., the machine itself and its connected

devices such as monitor, keyboard, and mouse etc., as well as software that makes use

of hardware for performing various functions.

What is a Computer?

Computer is a device that transforms data into meaningful information. Data can be

anything like marks obtained by you in various subjects. It can also be name, age, sex,

weight, height, etc. of all the students in a class. Computer can also be defined in

terms of functions it can perform. A computer can i) accept data, ii) store data, iii)

process data as desired, and iv) retrieve the stored data as and when required and v)

print the result in desired format. The major characteristics of a computer are high

speed, accuracy, diligence, versatility and storage.

Functions of Computer: The computer performs basically five major operations of functions irrespective of

their size and make. These are 1) it accepts data or instruction by way of input, 2) it

stores data, 3) it can process data as required by the user, 4) it gives results in the form

of output, and 5) it controls all operations inside a computer. We discuss below each

of these operations.

Input:

This is the process of entering data and instructions into the computer system.

Data:

Data refers to unprocessed text, numbers, images, audio, and video.

Instructions:

Instructions refer to Programs, Commands and User responses.

Control Unit (CU):

The process of input, output, processing and storage is performed under the

supervision of a unit called 'Control Unit'. It decides when to start receiving data,

when to stop it, where to store data, etc. It takes care of step -by-step processing of all

operations inside the computer.

Memory Unit:

Computer is used to store data and instructions.

Arithmetic Logic Unit (ALU):

The major operations performed by the ALU are addition, subtraction, multiplication,

division, logic and comparison.

Output:

This is the process of producing results from the data for getting useful information.

The ALU and the CU of a computer system are jointly known as the central

processing unit (CPU). You may call CPU as the brain of any computer system.

Peripheral Devices:

Peripheral devices are connected to the computer externally. These devices are used

for performing some specific functions. Peripheral devices are as follows:

1. Input Devices

2. Output Devices

3. Other Peripherals

4. Data Entry Operations



Input Devices: The data and instructions are given to the computer as input. The input device is used

to give input to the computer. It accepts input (data & program instructions) in a form

that a computer can use, and then sends it to the processing unit. The input unit is

formed by the input devices attached to the computer. An input unit takes the input

and converts it into binary form so that it can be understood by the computer.

Input devices accept data and instructions from the user. Following are the examples

of various input devices, which are connected to the computer for this purpose.

1. Keyboard

2. Mouse

3. Light Pen

4. Optical/magnetic Scanner

5. Touch Screen

6. Microphone for voice as input

7. Track Ball

8. Bar Code Reader

9. Digital Camera

1. Keyboard

A keyboard (as shown in figure 1.3) is the most common input device. Several kinds

of keyboards are available, but they resemble each other with minor variations. The

keyboard in most common use is the QWERTY board. Generally standard keyboard

has 104 keys. In these keyboards, the cursor control keys are duplicated to allow

easier use of the numeric pad.

2. Mouse:

A mouse is an electro-mechanical, hand-held device. It is used as a pointer. It can

perform functions like selecting menu commands, moving icons, resizing windows,

starting programs, and choosing options. The most common mouse uses an internal,

magnetically coated ball, to detect the movement of the mouse across a flat surface,

usually a desktop. Now a days Optical or laser mouse is used to detect the movement.

All windows based applications today are designed to work with a mouse. A mouse is

used to replace hard-to-remember key combinations with easier "Point and Click"

actions. However, it cannot substitute all keyboard operations. It can be alternative for

commands based operations.

3. Light Pen:

An input device that utilizes a light-sensitive detector to select objects on a display

screen. A light pen is similar to a mouse, except that with a light pen you can move

the pointer and select objects on the display screen by directly pointing to the objects

with the pen.

4. Optical Scanner:

These devices are used for automatic data collection. The devices of this category

completely eliminate manual input of data. For example, the bar-code reader is

actually just a special type of image scanner. An image scanner translates printed Data

Entry Operations images into an electronic format that can be stored in a computer’s

memory, and with the right kind of software, one can alter a stored image. Another

example of scanner is optical character recognition (OCR) device, used by banks to

convert the scanned image of a typed or printed page into text that can be edited on

the computer.

5. Touch Screen:

Touch panel displays and pads are now being offered as alternatives to keyboard.

Here the input can be given through the computer screen, that accepts the input



through monitor; users touch electronic buttons displayed on the screen or they may

use light pen.

6. Microphone:

Microphone is an input device, which takes voice as input. The voice communication

is more error-prone than information through keyboard. There are two types of

microphones available

1. Desktop Microphone

2. Hand held Microphone

7. Track Ball:

Trackball, a pointing device, is a mouse lying on its back. To move the pointer, you

rotate the ball with your thumb, your fingers, or the palm of your hand. There are

usually one to three buttons next to the ball, which you use just like mouse buttons.

The advantage of trackballs over mouse is that the trackball is stationary so it does not

require much space to use it. In addition, you can place a trackball on any type of

surface, including your lap. For both these reasons, trackballs are popular pointing

devices for portable computers.

8. Bar Code Reader:

It is a device which is used to read the code from the products which are usually in the

form of Bars. It contains a light sensitive detector which identifies the values of the

bars on the product & converts them into numeric code. These Bar Readers are used

in Shopping malls in a very large scale.

9. Digital Camera:

As the name specifies, these camera stores the data digitally, which then can be stored

in the computer & can be stored for a long time. But it has very limited storage

capacity. These are very popular because of less expensive photographs & Speed.

Output Devices: Output devices return processed data that is information, back to the user. Some of the

commonly used output devices are:

1. Monitor (Visual Display Unit)

2. Printers

3. Plotter

4. Speakers

1. Monitor:

Out of all the output devices, monitor is perhaps the most important output device

because people interact with this device most intensively than others. Computer

information is displayed, visually with a video adapter card and monitor. Information

processed within the CPU, that needs to be visually displayed, is sent to video

adapter. The video adapter converts information from the format used, in the same

manner as a television displays information sent to it by a cable service. Two basic

types of monitors are used with microcomputers, which are as follows:

1. CRT

2. LCD

Cathode Ray Tube (CRT): CRT or Cathode Ray Tube Monitor is the typical monitor

that you see on a desktop computer. It looks a lot like a television screen, and works

the same way. This type uses a large vacuum tube, called cathode ray tube (CRT).

Liquid Crystal Displays (LCD): This type of monitors are also known as flat panel

monitor. Most of these employ liquid crystal displays (LCDs) to render images. These

days LCD monitor are very popular. When people talk about the capabilities of

various monitors, one critical statistic is the resolution of the monitor. Most monitors

have a resolution of at least 800 x 600 pixels. High-end monitors can have resolutions



of 1024 x 768 pixels or even 1280 x 1024 pixels. Thus monitors are available either in

low resolution or in high resolution.

2. Printer:

After a document is created on the computer, it can be sent to a printer for a hard copy

(printout). Some printers offer special features such as colored and large page formats.

Some of the most commonly used printers are:

1. Laser Printer

2. Ink Jet Printer

3. Dot Matrix Printer

4. Line Printer

Laser Printer: A laser printer produces high quality print that one normally finds in

publishing. It is extremely fast and quiet. Moreover, the operation of a laser printer is

easy with automatic paper loading and no smudging or messing up of ink ribbons.

The fastest laser printer can print up to 200 pages per minute in monochrome (black

and white) and up to 100 pages per minute in colour.

Ink-Jet Printer: An ink-jet printer creates an image directly on paper by spraying ink

through as many as 64 tiny nozzles. Although the image it produces is not generally

quite as sharp as the output of a laser printer, the quality of ink-jet images is still high.

In general, ink-jet printer offers an excellent middle ground between dot matrix and

laser printer. Like laser printer, an ink-jet printer is quiet and convenient, but not

particularly fast. Typically, an ink-jet printer is more expensive than a dot-matrix

printer, but costs only half as much as a laser printer.

Dot Matrix Printer: The dot matrix printer was very popular at one point of time. It

is a very versatile and inexpensive output device. In dot matrix printer the print head

physically "hits" the paper through the ribbon and produces text (or images) by

combinations of dots; hence the name dot matrix printer. Its speed is measured in

characters per second (CPS). Although it is less expensive, it is louder, slower and

produces lower print quality. Line Printer: A line printer is generally used with large

computer systems to produce text based data processing reports. Line printers are

high-speed printers with speeds ranging anywhere from 100 to about 3800 lines per

minute. In the past, print quality on line printers was not high. Developments in

technology are improving the print quality on line printers. These are in the cost range

of lacs of Rupees.

3. Plotter:

A plotter is a special kind of output device that, like a printer, produces images on

paper, but does so in a different way. Plotters are designed to produce large drawings

or images, such as construction plans for buildings or blueprints for mechanical

objects. A plotter can be connected to the port normally used by a printer. An array of

different colored pens in a clip rack and a robotic arm is part of plotter. The

instructions that a plotter receives from a computer consist of a color, and beginning

and ending coordinates for a line. With that information, the plotter picks up the

appropriate pen through its arm, positions it at the beginning coordinates drops the

pen down to the surface of the paper and draws to the ending coordinates. Plotters

draw curves by creating a sequence of very short straight lines. Plotters usually come

in two designs:

1. Flat Bed: Plotters of small size to be kept on table with restriction of paper size.

2. Drum: These plotters are of big size using rolls of paper of unlimited length.

4. Speaker:

Speakers are another type of output device, which allow you to listen to voice like

music, and conversation with people.



What is Memory? A computer's memory can be viewed as a list of cells into which numbers can be

placed or read. Each cell has a numbered "address" and can store a single number.

The computer can be instructed to "put the number 123 into the cell numbered 1357"

or to "add the number that is in cell 1357 to the number that is in cell 2468 and put the

answer into cell 1595". The information stored in memory may represent practically

anything. Letters, numbers, even computer instructions can be placed into memory

with equal ease. Since the CPU does not differentiate between different types of

information, it is the software's responsibility to give significance to what the memory

sees as nothing but a series of numbers.

In almost all modern computers, each memory cell is set up to store binary numbers in

groups of eight bits (called a byte). Each byte is able to represent 256 different

numbers (2^8 = 256); either from 0 to 255 or −128 to +127. To store larger numbers,

several consecutive bytes may be used (typically, two, four or eight). When negative

numbers are required, they are usually stored in two's complement notation. Other

arrangements are possible, but are usually not seen outside of specialized applications

or historical contexts. A computer can store any kind of information in memory if it

can be represented numerically. Modern computers have billions or even trillions of

bytes of memory.

The CPU contains a special set of memory cells called registers that can be read and

written to much more rapidly than the main memory area. There are typically between

two and one hundred registers depending on the type of CPU. Registers are used for

the most frequently needed data items to avoid having to access main memory every

time data is needed. As data is constantly being worked on, reducing the need to

access main memory (which is often slow compared to the ALU and control units)

greatly increases the computer's speed.

Computer main memory comes in two principal varieties: random-access memory or

RAM and read-only memory or ROM. RAM can be read and written to anytime the

CPU commands it, but ROM is pre-loaded with data and software that never changes,

therefore the CPU can only read from it. ROM is typically used to store the

computer's initial start-up instructions. In general, the contents of RAM are erased

when the power to the computer is turned off, but ROM retains its data indefinitely. In

a PC, the ROM contains a specialized program called the BIOS that orchestrates

loading the computer's operating system from the hard disk drive into RAM whenever

the computer is turned on or reset. In embedded computers, which frequently do not

have disk drives, all of the required software may be stored in ROM. Software stored

in ROM is often called firmware, because it is notionally more like hardware than

software. Flash memory blurs the distinction between ROM and RAM, as it retains its

data when turned off but is also rewritable. It is typically much slower than

conventional ROM and RAM however, so its use is restricted to applications where

high speed is unnecessary.

In more sophisticated computers there may be one or more RAM cache memories,

which are slower than registers but faster than main memory. Generally computers

with this sort of cache are designed to move frequently needed data into the cache

automatically, often without the need for any intervention on the programmer's part.

A CPU cache is a cache used by the central processing unit of a computer to reduce

the average time to access memory. The cache is a smaller, faster memory which

stores copies of the data from the most frequently used main memory locations. As

long as most memory accesses are cached memory locations, the average latency of



memory accesses will be closer to the cache latency than to the latency of main

memory.

How is memory measured?

Memory access time:

The amount of time a processor takes to read the data, instructions and information

from memory. A computer’s access time affects how fast the computer process data.

Computer Data Storage:

Computer data storage, often called storage or memory, is a technology consisting of

computer components and recording media used to retain digital data. It is a core

function and fundamental component of computers.

Storage Capacity:

Number of bytes (characters) a storage medium can hold:

What is a storage device?



What is access time?

Time it takes storage device to locate item on storage medium. Time required to

deliver item from memory to processor.

Types of Storage Devices: 1. floppy disk

2. Zip disk

3. Hard disk

4. CDs and DVDs

5. Tape

6. PC Card

7. Miniature mobile storage

Difference between Memory and Storage :

A metaphor: The file cabinet represents the computer's hard disk, which provides

storage for all the files and information you need in your office. When you come in to

work, you take out the files you need from storage and put them on your desk for easy

access while you work on them. The desk is like memory in the computer: it holds the

information and data you need to have handy while you're working.

The two terms are sometimes used interchangeably, so it is important to understand

some key differences.

1. The term memory refers to the amount of RAM installed in the computer,

whereas the term storage refers to the capacity of the computer’s hard disk.

2. Both terms are used to refer to internal storage space on a computer. Memory,

usually referred to as Random Access Memory (RAM), is the place where an

application loads its data during processing, while a hard disk drive is usually

the place where data is stored for long or short term retention.

3. Memory dumps everything when you turn off your computer, in nature but

the hard drive retains what is stored on it.

4. Memory is typically volatile Storage is typically non-volatile.

5. Memory is quite a lot faster than hard drive.



6. Computer storage is typically cheaper, slower while computer memory is

expensive and faster

How does volatility compare?

Storage medium is nonvolatile contents retained when power is off. Memory is

volatile holds data and instructions temporarily.



Basic Concepts of the Computer Hardware: The physical components of a computer are called Hardware. Computer hardware

includes all the electrical, mechanical, and the electronic parts of a computer. Any

part that we can see or touch is the hard ware. The input/output devices (such as

Keyboard, Mouse, Printer, Monitor), CPU, Memory unit etc. are the examples of

hardware.

Computer Hardware includes:

System Unit

Secondary Devices

Input devices i.e. keyboard, mouse etc.

Output devices i.e. Display Unit, printer etc.

Storage devices like hard disk, floppy disks etc.

The following is a list of the most common hardware found on office and home

computers.

Monitor

CPU

Keyboard

Mouse

Scanner

Laptop

Hard Disk

USB Flash Drive

Floppy Disk

CD Rom

Printer

Central Processing Unit: A central processing unit (CPU), also referred to as a central processor unit, is the

hardware within a computer that carries out the instructions of a computer program by

performing the basic arithmetical, logical, and input/output operations of the system.

The term has been in use in the computer industry at least since the early 1960s. The

form, design, and implementation of CPUs have changed over the course of their

history, but their fundamental operation remains much the same.

In older computers, CPUs require one or more printed circuit boards. With the

invention of the microprocessor, a CPU could be contained within a single silicon

chip. The first computers to use microprocessors were personal computers and small

workstations. Since the 1970s the microprocessor class of CPUs has almost



completely overtaken all other CPU implementations, to the extent that even

mainframe computers use one or more microprocessors. Modern microprocessors are

large scale integrated circuits in packages typically less than four centimeters square,

with hundreds of connecting pins.

A computer can have more than one CPU; this is called multiprocessing. Some

microprocessors can contain multiple CPUs on a single chip; those microprocessors

are called multi-core processors.

Two typical components of a CPU are the arithmetic logic unit (ALU), which

performs arithmetic and logical operations, and the control unit (CU), which extracts

instructions from memory and decodes and executes them, calling on the ALU when

necessary.

Not all computational systems rely on a central processing unit. An array processor or

vector processor has multiple parallel computing elements, with no one unit

considered the "center". In the distributed computing model, problems are solved by a

distributed interconnected set of processors.

Software: As you are aware, computer cannot do anything on its own. It is the user who instructs

computer; what to do, how to do and when to do. In order to perform any task, you

have to give a set of instructions in a particular sequence to the computer. These sets

of instructions are called Programs. Software refers to a set of programs that makes

the hardware perform a particular set of tasks in particular order.

Classification of Software:

1. System Software

2. Application Software

3. Generalized Packages

4. Customized Packages

1. System Software:

When you switch on the computer the programs stored in ROM are executed which

activates different units of your computer and makes it ready for you to work on it.

This set of programs can be called system software. System softwares are sets of

programs, responsible for running the computer, controlling various operations of

computer systems and management of computer resources. Operating System (OS)

falls under this category. An operating system is a system software that provides an

interface for a user to communicate with the computer, manages hardware devices

(disk drives, keyboard, monitor, etc), manages and maintains disk file systems and

supports application programs. Some popular Operating systems are UNIX, Windows

and Linux. Although operating system provides all the features users need to use and

maintain their systems, inevitably, they still do not meet everyone’s expectations. This

has led to another type of system software called "Utilities". These are programs that

bridge the gap between the functionality of an OS and the needs of users. Utility

programs are a broad category of software such as compress (zip)/uncompress (unzip)

files software, antivirus software, split and join files software, etc.

2. Application Software:

Application software is a set of programs, which are written to perform specific tasks,

for example: An application package for managing library known as library

information system is used to manage information of library such as: keeping book

details, account holder details, book issue details, book return details etc. Another

application package for managing student details is called student’s information

system, manages student’s roll no, name, parents name, address, class, section,



processing of examination results etc. Application software can be broadly classified

into two types:

(a) Generalized packages

(b) Customized packages

3. Generalized Packages:

These are user friendly softwares written to cater to user’s very general needs such as

preparing documents, drawing pictures, database to manage data/information,

preparing presentations, play games etc. It is a group of programs that provide general

purpose tools to solve specific problems. Some of the generalized packages are listed

below:

Word Processing Software (for preparing documents): Word Perfect, MS-

Word, OpenOffice.org Writer,

Spreadsheets (Data Analysis): Lotus Smart suites, MS Excel, OpenOffice.org

Calc, Apple Numbers, Presentations : Presentation Graphics, MS-PowerPoint,

OpenOffice.org Impress,

Database Management System: MS-Access, OpenOffice.org Base, MS-SQL

Server, ORACLE,

Graphics Tools: Paint shop pro, Adobe Photoshop

4. Customized Packages:

These are the applications that are customized (or developed) to meet the specific

requirements of an organization/institution. For Example: Student information details,

Payroll packages, inventory control etc. These packages are developed using high-

level computer language.

Computer Languages: Languages are a means of communication. Normally people interact with each other

through a language. On the same pattern, communication with computers is carried

out through a language. This language is understood both by user and the machine.

Just as every language like English, Hindi has its grammatical rules; every computer

language is bound by rules known as SYNTAX of that language. The user is bound

by that syntax while communicating with the computer system. Computer languages

are broadly classified as:

1. Low Level Language:

The term low level means closeness to the way in which machine understand. The

low level languages are:

Machine Language:

This is the language (in the form of 0’s and 1’s, called binary numbers) understood

directly by the computer. It is machine dependent. It is difficult to learn and even

more difficult to write programs.

Assembly Language:

This is the language where the machine codes comprising of 0’s and 1’s are

substituted by symbolic codes (called mnemonics) to improve their understanding. It

is the first step to improve programming structure. Assembly language programming

is simpler and less time consuming than machine level programming, it is easier to

locate and correct errors in assembly language than in machine language programs. It

is also machine dependent. Programmers must have knowledge of the machine on

which the program will run.

2. High Level Language

You know that low level language requires extensive knowledge of the hardware

since it is machine dependent. To overcome the limitation, high level language has



been evolved which uses normal English like, easy to understand statements to solve

any problem. Higher level languages are computer independent and programming

becomes quite easy and simple. Various high level languages are given below:

BASIC (Beginners All Purpose Symbolic Instruction Code):

It is widely used, easy to learn general purpose language. Mainly used in

microcomputers in earlier days.

COBOL (Common Business Oriented language): A standardized language used for commercial applications.

FORTRAN (Formula Translation):

Developed for solving mathematical and scientific problems. One of the most popular

languages among scientific community.

C:

Structured Programming Language used for all purpose such as scientific application,

commercial application, developing games etc.

C++:

Popular object oriented programming language, used for general purpose.

Compiler and Assembler:

As you know that High Level language is machine independent and assembly

language though it is machine dependent yet mnemonics that are being used to

represent instructions are not directly understandable by machine. Hence to make the

machine understand the instructions provided by both the languages, Compiler and

Assembler are required to convert these instructions into machine language.

The software (set of programs) that reads a program written in high level language

and translates it into an equivalent program in machine language is called as

Compiler. The program written by the programmer in high level language is called

source program and the program generated by the compiler after translation is called

as object program. The software (set of programs) that reads a program written in

assembly language and translates it into an equivalent program in machine language is

called as Assembler.

Functions of Computer: The Four Basic Functions of a Computer

Input:

Input devices enable us to get information into a computer. Some examples include a

keyboard, mouse, microphone, scanner, or digital camera.

Storage:

There are two types of storage: temporary and long-term. RAM, or random access

memory, is temporary, meaning it stores information as you use it, but it is being

constantly erased and rewritten as you open and close files. Long-term storage holds

information for as long as you want it. Hard drives, portable hard drives, floppy

drives, flash drives, CD’s, and DVD’s are long term storage devices.

Processor:

A microprocessor controls the computers’ functions. It is smaller than a dime, but

contains millions of transistors that perform millions of instructions per second. The

microprocessor performs these instructions using a three-step process: fetch, decode

and execute.

Output:

Information that has been processed is communicated back to the user in the form of

words, sounds or pictures, and is delivered through printers, speakers, monitors or

other output devices. Sometimes output is just written back to a storage device.



Benefits of Computer in Education: 1. Computer can make education more productive.

2. Computer can make education more individual.

3. Computer can give instruction a more scientific base.

4. Computer can make instruction more powerful.

5. Computer can make access to education more equal.

The stated features of computer show that it is almost covering all the aspects of

educational technology is properly used, these benefits can be used to enhance the

teaching learning process.

Role of Educational Technology:

Educational Technology is rightly considered with developing interests of children in

classroom. These interests enhance the learning speed.

“Educational technology enables a large mass of the target population to learn certain

specified skills, behaviors, values and knowledge, in the fastest, and in the most cost

effective way.” (Rashid, 1993, p.258).

The strength of educational technology shows its future role in educational process.

The researchers indicate some problems like population growth, information growth,

and demand for higher and future education, teaching shortage, and existing limitation

of recourses faced by educational system today. These problems are being faces by

developed as well as developing countries. The following long-term measures to

counter the problems:

1. Carry out curriculum reform.

2. Carry out manpower forecasting.

3. Improve teaching materials, aids etc.

4. Utilize new methods of instructions.

5. Research in teaching methods, system and factors affecting their efficiency.

6. Improve teacher training.

7. Make innovation in architectural design.