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1
Basics of Computer
1.1 INTRODUCTION
In this lesson 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 lesson we will discuss about hardware, i.e., the machine itself and its connected devices such as monitor, keyboard, mouse etc., as well
as software that makes use of hardware for performing various functions.
1.2 OBJECTIVES
After going through this lesson you
would be able to:
l explain basic organization of computer system
l explain different types of input and output devices
l define
Software and its classification
l distinguish between system software
and application software
l describe computer language and its classification
2 :: Data Entry Operations
1.3 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.
1.3.1 Computer
Organisation
The block diagram of computer is
shown in Fig.
1.1.
Memory Unit
Input unit
Control Unit
Output unit
Arithmetic
Logic Unit
Fig. 1.1 Block diagram
of Computer Organisation
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.
1. Input: this is the process of entering data and programs into the computer system.
Basics of Computer :: 3
2. 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 in side the computer.
3. Memory Unit:
Computer
is used to store data
and instructions.
4. Arithmetic Logic Unit (ALU):
The major operations performed by
the ALU are addition, subtraction, multiplication, division, logic
and comparison.
5. 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.
INTEXT QUESTIONS
1. What are the five basic operations performed by
the computer?
2. Define ALU, CU and CPU.
3. Choose the correct answer.
(a) The task of
performing arithmetic and logical operations is called:
(i) ALU (ii) editing (iii) storage (iv) Output
(b) The
ALU and CU jointly are known as
(i) RAM (ii) ROM (iii)
CPU (iv) None of above
(c) The process of producing results from the data for getting useful information is called:
(i) output (ii) input (iii) processing (iv) storage
1.4 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
Monitor
Disk drives
Keyboard
Mouse
Fig. 1.2 Different peripheral devices of Computer
1.5 INPUT DEVICES
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
1.5.1 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.
Fig. 1.3 Keyboard
Basics of Computer
:: 5
1.5.2 Mouse
A mouse is an electro-mechanical, hand-held device (as
shown in figure 1.
4). It
is used as a pointer.
It can perform
functions like selecting menu commands, moving icons,
resizing windows, starting programs, and choosing options.
Fig. 1.4 Mouse
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.
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1.5.3 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 (as shown in figure 1.5), 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.
1.5.4 Optical
Scanner
Fig. 1.5 Light Pen
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
6 :: 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.
1.5.5 Touch Screen
Fig. 1.6 Scanner
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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.
Fig. 1.7 Touch Screen Monitor
1.5.6 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 (as shown in
figure 1.8):
1. Desktop Microphone
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2. Hand held Microphone
Fig. 1.8 Desktop microphone and Hand-held Microphone
1.5.7 Track Ball
Trackball, a pointing device,
is a mouse lying on its back
(as shown in figure 1.
9). 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.
Fig. 1.9 Track Ball
Basics of Computer :: 7
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.
1.6 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
1.6.1 Monitor
Out of all
the output devices, monitor (as
shown in figure
1 .10 ) is
perhaps the most important output device because people
interact with
this device most intensively than others . Computer information is displayed,
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Fig. 1.10 CRT and LCD Monitor
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.
8 :: Data Entry Operations
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.
1.6.2 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
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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 Fig. 1.11 Laser Printer
Basics of Computer
:: 9
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
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Fig. 1.12 Ink-Jet
Printer
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.
Fig. 1.13 Dot Matrix
Printer
Fig. 1.14 Line Printer
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1.6.3 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.
Fig. 1.15 Flat bed and Drum Plotter
1.6.4 Speaker
Speakers (as shown in figure 1.16) are another type of
output device, which allow
you to listen to voice
like music, and conversation with people.
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Fig. 1.16 Speaker
Basics of Computer
:: 11INTEXT QUESTION
4. Write True or
False for
the following:
(a) Mouse is an output device.
(b) OCR stands for Optical Content Reader.
(c) LCD Monitor is
used in notebook computer.
(d) Speed of DOT Matrix Printer is measured in
Characters Per Second.
(e) Plotters are used to produce high quality drawings and images, such as construction plans for buildings or
blueprints for mechanical objects.
1.7 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. Software can be
classified mainly into following
categories and
sub-categories are shown in Figure 1.17.
Software
System Software Application Software
Operating
System
Utilities
Generalized
Packages
Customized
Packages
Fig. 1.17 Classification of Software
12 :: Data Entry Operations
1.7.1 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, anti virus software, split and join
files
software, etc.
1.7.2 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
Basics of Computer
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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:
l Word Processing Software(for preparing documents): Word
Perfect, MS-Word, OpenOffice.org Writer
l Spreadsheets (Data Analysis):
Lotus Smart suites,
MS- Excel, OpenOffice.org Calc, Apple Numbers
l Presentations : Presentation Graphics,
MS-PowerPoint,
OpenOffice.org Impress
l Database Management System: MS-Access, OpenOffice.org Base, MS-SQL
Server, ORACLE
l Graphics Tools: Paint shop pro, Adobe Photoshop
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.
1.8 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.
14 :: Data Entry Operations
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:
a. 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.
b. 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:
l BASIC (Beginners All Purpose Symbolic Instruction
Code): It is widely used, easy to
learn general purpose
language. Mainly used in microcomputers in earlier days.
Basics of Computer
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l COBOL (Common Business Oriented
language): A
standardized language used for commercial applications.
l FORTRAN (Formula
Translation): Developed
for solving mathematical and scientific problems. One of the most popular languages among scientific community.
l C: Structured Programming Language used for all purpose such as scientific application, commercial application,
developing games etc.
l C++: Popular object oriented programming language, used for general purpose.
1.9 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.
Source Program
(Higher Level Language)
Compiler
Object Program
(Machine Language)
Fig. 1.18 Compiler
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.
16 :: Data Entry Operations
Source Program
(Assembling Language)
Assembler
Object Program
(Machine Language)
Fig. 1.19 Assembler
INTEXT QUESTION
5. Write True or False for the following:
(a) Operating System (OS) is an Application Software. (b) High level
languages are easy to program than low
level language.
(c) Computer language FORTRAN is used to solve
Scientific and Mathematical problems.
(d) C is
an object
oriented programming language.
(e) Compiler converts high level
languages into machine language.
1.10 WHAT YOU HAVE
LEARNT
A computer is
useful only when it
interacts with the external
devices such as keyboard,
mouse, monitor, speaker, which are called as peripheral devices. In
this lesson we have discussed in details about major peripheral devices of a computer
system. You have learnt that only
hardware does not do anything of its own without the help of software. Hence we have explained
in details about software,
its types and the computer languages
used to prepare the software.1.11 TERMINAL QUESTIONS
1. What is a computer? Draw a block diagram to illustrate the basic organisation of a computer system and explain the functions of various units.
2. What is an input device? Briefly
describe varioius important input devices.
3. Discuss two
basic types of monitors CRT and LCD.
Basics of Computer
:: 17
4. What is a software? Discuss its various categories with the help of
diagram.
5. Distinguish between system and application software.
6. Write short
notes on: (a) Laser Printer
(b) High
level language
(c) Compiler
(d) Plotter
7. Write a note on
Computer language and its classification.1.12 FEEDBACK TO INTEXT QUESTIONS
1. The
five basic operations that a computer
performs are input, storage,
processing, output and control.
2. ALU : Arithmetic Logic
Unit
CU : Control Unit
CPU : Central Processing
Unit
3. (a) i (b) iii (c)
i
4. (a) False (b) False (c) True (d) True (e) True
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