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.

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