Hardware
Fig 06:
Keyboard
Fig 07:
Mouse
Fig 10: Floppy disk
Fig
12: CD-ROM
Def:
The physical, tangible parts of the computer
are known as the hardware.
Hardware
can be broadly categorized into four:
a) Input Devices
b) Processor Devices
c) Output Devices
d) Storage Devices
Input
Devices:
1.
Keyboard: It
is the main Input Device attached to our system to instruct the computer to
what to do and also used for typing purpose.
Its typing alphabets
are similar to that of type writer but it has some optional keys which are
F Functional Keys
F Cursor Control Keys
F Numeric Key Pad
F Shift Keys
F Enter, Pause, Tab,
Esc, Print Screen, Delete, Back Space etc.
2.
Mouse: A mouse is a hand held pointing Device that
allow user to control computer System without typing any command or Instruction
from the Keyboard. It has three main
parts
F Left Click
F Right Click
F Scroll Bar
3.
Scanners: A
scanner is a device that can transfer an image of a photograph or written
information to the computer. It acts like a photocopy machine. Just Instead of
making another copy of it on to the paper, it stores it in the computer.
Scanner can scan typed, handwritten text, graphs, diagrams and photographs.
Fig 08: Scanner.
Processor
Device:
C.P.U.
(Central Process Unit) :
It is
regarded as brain of Computer. The CPU provides the fundamental commands and
instructions for the environment of the Computer.
The
major components of CPU are
F Arithmetic Logic Unit (ALU)
F Control Unit (CU)
F Memory Unit.
Fig 09: Block
Diagram
- Arithmetic Logic Unit: The Arithmetic logic unit performs
arithmetic operations such as Addition, Subtraction, Multiplication and
Division etc and some logical operations like comparison of Values.
- Control Unit Control Unit directs and
coordinates the activities of the entire computer which include
controlling the Input/Output units, the operations of ALU and transfer the
data from the main memory
- Memory Unit: The data and Instruction that are entered into the system has to
be stored inside the computer before the actual processing takes place.
Similarly the final result produced by the computer also has to be stored
before they passed to the output unit.
Output
Devices:
1.
V.D.U. (Visual Display Unit): It is also called Monitor. It works like a
Television, displaying text characters and graphics in color. The image that we
see at the screen of Monitor is made up of Tiny Dots called Pixels. It is made
up of C.R.T. (Cathode Ray Tube) is similar to Picture tube in Television Sets.
Modern Monitors are made up of L.C.D. (Liquid Crystal Display) screen.
2.
Printers:
A hardware device
that produce text or graphics output. Printers are grouped broadly into either
Impact or Non-Impact printers
F Impact
Printers: A printer that has
direct mechanical contact with the print medium (Paper) to create an image. Example: Dot Matrix, Daisy Wheel
F Non-Impact
Printers: The printer that
does not have direct contact with the print medium falls under this category. Example: Inkjet Printers, Laser
Printers
Storage
Device:
1. Floppy disk: A floppy disk is used to store data
permanently. It has a flexible disk coated with magnetic material and is
enclosed in a plastic cover. Floppy disks of 3 ½ inch diameter have a storage
capacity of 1.44MB. The FDD (floppy disk drive) has a read/write head which
reads/writes data on to the disk. The disk rotates at 360rpm while reading or
writing on to it. Figure below shows the floppy disk.
Data are stored in a floppy disk in concentric circles known as tracks. Tracks are divided into many storage locations called sectors. Tracks and sectors on a disk are identified by the disk drive through formatting. Formatting is a process by which the operating system program controls the disk drives by removing the old data and sets up each track and sector. The root directory will be created in the disk during formatting and the users create other directories. Information is stored in the form of files. A file allocation table (FAT) is used by the operating system to identify the files stored in the disk.
Data are stored in a floppy disk in concentric circles known as tracks. Tracks are divided into many storage locations called sectors. Tracks and sectors on a disk are identified by the disk drive through formatting. Formatting is a process by which the operating system program controls the disk drives by removing the old data and sets up each track and sector. The root directory will be created in the disk during formatting and the users create other directories. Information is stored in the form of files. A file allocation table (FAT) is used by the operating system to identify the files stored in the disk.
2. Hard Disk: Hard disk is a
reliable and permanent storage disk. It has a set of metal disks coated with
magnetic material and are mounted on a central spindle which rotates at 7200
rpm. The HDD has a set of read/write heads which are mounted on an arm. Latest
hard disks are available with a storage capacity of more than 40GB. A hard disk has a collection of several (say
6 or 7) hard disk platters staked one above another to have a high storage
capacity.
A
collection of tracks across all the disks is called cylinder. In order to read
a specified file, the access mechanism with the head moves to the specified
cylinder.
The
advantages of a hard disk are high storage capacity, high speed of operation
and reliable media mainly in personal computers. External disturbances to the
drive may lead to the damage of disk surface or read/write head. This is a
major disadvantage in a hard disk.
Fig 11: Hard disk
3. CD ROM: Compact Disk
(CD) is an optical disk used to store data permanently. It is the most reliable
storage media available today. Data stored on a compact disk cannot be erased.
The CD drives commonly available are read only. Read/Write CD drives are also
available but are expensive. Storage capacity of CD is 700MB. Figure shows a
CD-ROM.
In
the optical disk, a high power laser beam is used to record data by burning
tiny pits in the surface of the hard plastic disk. To read the data, a low
power laser beam is used to scan the disk surface. When the laser beam reflects
from the smooth surface of the disk it is interpreted as a 1 bit and when the
beam enters the tiny pits it is interpreted as a 0 bit.
The
major advantages of the optical disk are high storage capacity and high quality
recording of graphical images and sound. These are used commonly nowadays. CAD
and structural drawings used by architects and engineers are generally stored
in compact disks. It is also used in high quality music recording, multimedia
and educational applications.
*****
Components of a personal computer:
A
personal computer commonly available
today comprises a processor (like Pentium IV), a keyboard, a mouse, a
floppy disk drive(FDD), a hard disk drive(HDD), a compact disk drive (CDD) a
color monitor, RAM(Random Access Memory) and ROM(Read Only Memory). The
microprocessor/CPU, RAM, ROM and other supporting circuitry are interconnected
on a single board called mother board.
*****
Software:
Def:
The set or series of instructions given by
user, called program, used to run the hardware, is known as software.
The following are the two major
categories of software under which different types of computer programs can be
classified:
·
System software
·
Application software
Fig 13: Layered
Architecture
The figure shows
a layered architecture, which represents different components of a computer
such as hardware, system software, application software, and user in a
hierarchical manner.
System
Software
Ø System
software refers to a computer program that manages and controls hardware
components of a computer system.
Ø The
system software is also responsible for the proper functioning of the
application software on a computer system.
Ø The
system software includes general programs, which are written to provide an
environment for developing new application software using programming
languages.
Ø The
following are the various functions of system software:
o
Process management
o
Memory management
o
Secondary storage management
o
I/O system management
o
File management
Application
Software
Ø Application
software is a computer program that is executed on the system software.
Ø It is
designed and developed for performing specific tasks and is also known as
end-user program.
Ø There
are six basic types of application softwares:
o
Business software:
word processors, spreadsheets, database programs
o
Communication software:
allows computers to communicate with other computers like fax software, Novell
Netware, AOL, Modem software
o
Graphics software:
software that allows users to create and manipulate graphics like Photoshop,
Print Shop, etc.
o
Education and Reference software:
programs that help teach new material and ideas, and programs that can be used
to find information like Encarta, Wordbook Encyclopedia, Jumpstart
Kindergarden,etc.
o
Entertainment and Leisure software:
like War craft, Age of Empires, Barbie Design Center, Packman, Solitaire, etc.
o
Integrated software:
combines several types of software into one program or package like Quicken(Spreadsheet/database/communication/reference)
or PrintShop(Graphics/Word processor)
