Major Components of Computer:-
Computer is basically composed of essentially the following:
1. Hardware
2. Software
1. Hardware: Computer hardware is the collection of various physical
components of the computer, like the computer itself, the input-output
devices. This computer Hardware performs some operations like
addition, Subtraction, data transfer, control transfers and simple tests.
2. Software: Software is set of instructions usually termed as programs
which are required for processing activities of the computer. These
set of programs can be used to solve real world problems. The capability
of computer depends upon the software components.
Input Unit: The process of sending the data and Instructions for the
processing through some suitable devices such as Keyboard, Mouse
etc. is called Input. The devices translate the data from human
understandable form into electronic impulses which are understood
by the computer.
Central Processing Unit (CPU):- Once the data accepted it fed in
to Central Processing Unit before the output is generated as data has
to be processed, which is done by CPU. This unit of the computer is
the brain of computer system, which does all the processing,
calculations, problem solving and controls all other functions of all other
elements of the computer. The CPU consists of the following three
distinct units namely.
1. Memory Unit
2. Control Unit
3. Arithmetic and Logic Unit
1. Memory Unit: Which holds the data in in terms of Program and files.
The data stored can be accessed and used whenever required by the
CPU for necessary processing. This memory unit is usually referred as
primary storage section. The units in which memory unit is measured are
known as BYTES.
BYTE is the space required to store 8 characters or alphabet or digits
any other special character.
1 Byte = 8 Bits.
1 Kilobyte = 1024 Bytes
1 Megabyte = 1024 Kilobytes
1 Gigabyte = 1024 Megabytes
1 Terabyte = 1024 Giga bytes
Where Bits are spaces required to store one Binary digits i.e. either 0
or 1.
2. Control Unit : This unit which coordinates all the activities of each
and every element of computer. It decodes the instructions given by
various users and it sends commands and signals that determine the
sequence of various instructions. Through this unit does not process
data but it acts as the central system for data manipulation, as it
controls the flow of data to and from the main storage.
3. Arithmetic and Logic Units:- This unit performs arithmetic operations
such as addition,substraction,multiplication and division. It also does
Logical Operations such as comparison of numbers etc. Thus this
unit helps by processing data and taking logical decisions.
Output: - The processing of extracting the data from CPU through some
suitable devices is called Output. The common used output devices are
VDU, Printers, Plotter, magnetic media like floppy, hard disks etc.
Types of Memories:-
The memory used by computers can be classified
into various types. Some of the commonly available memory types are
1. Magnetic Core Memory: This is the memory which uses small
magnetic cores with wires running through then and electric current
which flows through these wires, which generates magnetic field.
Depending on direction of current and magnetic field, data is
represented. The semiconductor based memories are RAM,ROM.
2. Random Access Memory(RAM):- While a program being is
executed it requires data, such data is stored in RAM,. The data
stored in RAM is volatile i.e. when there is a power failure the data
in the RAM is lost. Whenever new data is stored in RAM the
previous data is erased.
3. Read on Memory (ROM): Which contain the Bootstrap Loader
Programs, which loads the Operating System(O.S) into memory.
As this program is stored in ROM, it starts as soon as the computer
is switched on and makes the computer ready to load OS program
in the memory. The contents of ROM cannot changed but for
specialized use contents of ROM can be re-programmed using
special circuits.
4. Cache Memory: This is very high speed memory which is used to
store portion of a program from main memory temporarily. The
Cache memory very expensive, but it is very fast,. The data is
transferred automatically between the buffer and primary storage,
which lies between main memory and Microprocessor.
Communication Paths:
The CPU consists of Memory Unit, Control Unit, and Arithmetic
and Logic Unit (ALU). The Communication links between
these three units are called buses. The buses are the electrical
paths for data to flow from point to point in a circuit.
The Buses for Communication in CPU are 1. Control Bus
2.Address Bus 3. Data Bus
1. Control Bus: - The Path for all controlling and timing functions
sent by the control unit to other units of CPU.
2. Address Bus: - This Path is used for locating the address of the
memory location where the next instruction to be executed or the
next piece of data is found. This is used for data retrieval storage
and manipulations where address of storage locations are required.
3. Data Bus:- This is the path on which actual data transfer takes
place.
SOFTWARE: -
Collection of Programs are Software. The Software is those
components which make the task of a user complete, as it is that component
which helps a user to give set of instructions. The Software is categorized
on the basis of functions they are
1. System Software 2 .Application Software
1. System Software:- Which controls all processing activities and
makes sure that the resources and the power of the computer are
used in most efficient manner . The System software can
categorized in to
1. Operating System
2. Language Processors ( Assemblers, Compilers,
Interpreters)
3. Device Drivers
4. Utility Programs etc
The System software as a package which consists of various
programs required for the functioning of the computer itself. It is also needed
for translation, loading, controlling and running of the program.
The system software basically serves TWO major purposes.
a. It controls the execution of programs on the computer.
b. It helps the development of software.
1. Operating System :- Which is set of programs that controls and
support hardware and provide various services which are used for
better performance of computer
. The major functions of O.S are
1. It assigns processors to tasks
2. It manages memory and other storage areas
3. It acts as a command interpreter
4. File management
5. Input-Output Management
6. Establishing data security & Integrity
7. Maintains account of processor time for billing purposes.
8. Provides data and time services etc.
The Operating systems can be classified as Single user and Multiuser
(number of users working on it at a given point of time) and
Multitasking operating systems,
Single user Operating systems - MSDOS
Multi-user Operating System - UNIX, Linux etc
Multitasking Operating System - Windows
2. Language Processors:-
Translators: As the computer accepts digits and characters as
input, such input to be conversed. Into machine language. The Software
which makes conversion possible and increases the productivity of
the programmer are called Translators.
There are three basic types of translators they arei. Compilers ii. Interpreters iii. Assembler
i. Compilers: - A compiler is a software that will convert
the high level instructions into equivalent Machine level
instructions at a time.
ii. Interpreters:- A Interpreter is a software that will
convert the high level instructions into equivalent
Machine level instructions step by step.
iii. Assembler:- Assembler is a software that will convert
the high level instructions into equivalent Machine level
instructions but here, the input programs are in assembly
language. The output is in machine language.
2. Service Utilities:These utilities are those software programs which are provided by the
manufacturer of various hard wares to perform specific tasks which
are common to all data processing installations.
The commonly available service utilities are:
a) Device Drivers
b) Directory and File management Utilities.
a) Device Drivers: These are special programs which are used to
enhance the capability of operating systems, so that it can support
many input/output devices like mouse, joysticks, printers etc.
b) Directory and File management Utilities: These are those
software programs which are used to manage data.
II. APPLICATION SOFTWARE:This is that software which serves specific purposes and allows the
user to create applications which are for a given purpose like financial
accounting, payroll examinations, human resources management
etc.
These software can be further classified, depending upon the source
of development as well the users:i) Pre written application software.
ii) User written application software.
i) Pre written application software.
These are those software packages which are developed by
group of people or an individual to be used by others.
The most commonly available prewritten application software
are:
i) Word processing software
ii) Electronic spreadsheets
iii) Database management software
iv) Graph generator
v) Report generator
vi) Communication software
i) Word processing Software : These are those
software, which usually automate the day today
documentation work of an organization.
ii) Electronic spreadsheets : Electronic spreadsheets
are like sheets are of paper with rows and columns.
Electronic spreadsheets allow numbers, characters,
formulas and all other types of data which has to be
entered in a tabular form into rows or columns. Some
of the significant advantages are:-
a) It provides flexibility and it is easy to incorporate
changes.
b) Automation of various calculations.
c) Flexibility to size and resize columns.
Some of the most commonly available and used spreadsheets are Lotus-
1, 2, 3, MS-Excel, Super Calc etc.
Database management software: Database is an organized collection
of data, which is logically related.
Graph generator: As graphical representation of data is much more easy
to understand as well is appearing, when the data presented in graphical
from like Bar graphs, Pie charts, Line graphs etc. is called Graph generator.
Some of the graphics generators are Lotus 123, Oracle graphics, MS Excel
etc.
iii) Report generator: There is always a need in day to day operations
that timely reports of various activities have to be used, so as to depict, a
situation or helping decision making.
iv) Communication Software: Communication is the essence of all
operations. Effective commu8nication i.e., sending and receiving data plays
a key role in the smooth running of any organization.
1.6 Number SystemData is usually combination of Numbers, Characters and special
characters. The data or Information should be in the form machine readable
and understandable for his reason the data has to be represented in the
form of electronic pulses.
The data has to be converted into electronic pulses and each pulse
should be identified with a code. For these reasons, the data is converted
in to numeric format first, by using ASCII, where each every character,
special character and keystrokes have numerical equivalent. Thus using
this equivalent, the data can be interchanged into numeric format. For
this numeric conversions we use number systems, each number system
has radix or Base number , Which indicates the number of digit in that
number system.
Basically Number system is divided into
1. Binary Number System 2. Octal Number system
3. Decimal Number system 4. Hexa- Decimal Number System
1. 1. Binary Number system :- This system which represents only
two types of digits i.e 0’s and 1’s, so the radix number is this system is 2.
The advantage number system is that, as there are only two distinct digits
one can use only two electronic pulses to represent data. The two pulses
that are used to represented the digits of this number system i.e. 0 and 1
are
· Absence of pulses(current) for 0
· Presence of pulse(current) for 1
The value of the numbers is represented as power of 2 i.e. the radix of
the system. These power increases with the position of the digit
Position 6th 5th 4th 3rd 2nd 1st
Weight 25 24 23 22 21 20
Ex: Convert (10101)2 in to Decimal equivalent
10101 = 1 x 2 4 + 0 x 23 + 1 x 22 + 0 x 21 + 1 x 20
= 16 + 0 + 4 + 0 + 1 = (21)10
2. Octal Number System :- This number system has a radix of 8 and the
digit of this number system are 0 - 7. All the numbers are represented as
the combinations of 0 - 7.The position of the number determines its value
in this number system, which is power of 8 i.e.
Position 6th 5th 4th 3rd 2nd 1st
Weight 85 84 83 82 81 80
This number system has a concept of representing three binary digits as
one octal numbers, thereby reducing the number of digits of binary number
still maintaining the concept of binary system.
3.Decimal Number system:- The digits of this number system 0 .. 9.,
the radix of this number system is 10. In this system the value of a digit
depends upon position they occupy. These positions are in the multiplies
of 10 i.e the radix of the system.
Position 6th 5th 4th 3rd 2nd 1st
Weight 105 104 103 102 101 100
4. Hexa Decimal Number System:- The digits of this number system is
0 -15 (i.e the digit represented as A–10 is represented as B–11, C–13,
D–14, E–15, F–15) . The radix of this system is 16. In this system we
group four binary digits to represent hexadecimal numbers.
Ex : 7B72, 5C88, 4A51 etc.
Conversion of one number system to another number system:-1. Binary number system to Octal number system and voiceovers
2. Binary number system to Decimal number system and
voiceovers
3. Binary number system to Hexa Decimal number system and
voiceovers
4. Octal number system to Decimal number system and
voiceovers
5. Octal number system to Hexa number system and voiceovers.
6. Hexa Decimal number system to Decimal number system and
voiceovers
Arithmetic Operations using Binary system:- The basic arithmetic
operations which can be performed rising binary number system are:-
a. Addition b. Subtraction c.Multiplication d. Division
a. Binary Addition:- Binary addition is similar to decimal numbers.
The rules involved in carrying out the binary addition are as follows
0 + 0 = 0
1 + 1 = 1
1 + 0 = 1
1 + 1 = 0 with a carry over of 1.
Ex:- Add ( 10011110)2 and (11101101)2
Sol:- Binary Decimal
1 0 0 1 1 1 1 0 1 5 8
1 1 1 0 1 1 0 1 2 3 7
1 1 0 0 1 0 1 1 3 9 5
a. Binary Subtraction:- Binary subtraction is also very similar to
decimal susbstraction. The rules binary subtraction are
0 + 0 = 0
1 + 0 = 1
1 + 1 = 0
0 + 1 = 1 with one barrow
Ex: - Substract (1110110)2 from (1111101)2
Sol:- Binary Decimal
1 1 1 1 1 0 1 125
- 1 1 1 0 1 1 0 -
118
0 0 0 0 1 1 1 07
b. Binary Multiplication:- To
multiply binary numbers, the
rules which have to be
followed are as follows:
0 x 0 = 0
1 x 0 = 0
0 x 1 = 0
1 x 1 = 1
Ex:- Multiply (11110)2 by (100)2
Sol: Binary Decimal
1 1 1 1 0 30
1 0 0 x 4
0 0 0 0 0 120
0 0 0 0 0 x
1 1 1 1 0 x x
1 1 1 1 0 0 0
d. Binary division:- For binary division, the rules which are applicable
to the decimal system has to be followed and the rules of binary addition,
subtraction and multiplication have to be adhered to
Ex:- Divide (100011)2 by (111)2
Sol:- 111 ) 100011 ( 101
111
00111
111
00
Binary Complements:-
Def:- Replacing 0’s with and 1’s with 0 is called complement of given
number.
Ex:- Find the complement of ( 11111001)2
Given Number 1 1 1 1 1 0 0 1
1’s Complement 0 0 0 0 0 1 1 0
Complementary Subtraction:- This is for subtracting binary number from
given binary number One’s complement of a number is arrived at by
susbstracting each binary digit from 1
Ex:- Find out one’s complement of (1101001101)2
Sol:- To arrive at one’s complement substract each digit from 1.
1 1 1 1 1 1 1 1 1
1 0 1 0 0 1 1 0 1
1 0 1 0 1 0 0 1 0
Substraction using complements:-
Substraction using 1’s complement:-
Steps:- 1. Find one’s complement of the number to be subtracted.
2. Add the complement to the number
from which it has to be subtracted.
3. If there is carry of 1, at the end add that back to the resultant, to
get subtraction’s result.
4. If there is no carry i.e. o, then add o as no carry, then recomplement
15
it and attach a negative sign to get subtraction’s result.
Ex:- Subtract 1011 from 110111 by using 1’s complement.
1 0 1 1 0 1
+ 1 1 0 1 0 0
1 0 0 0 0 1 (add carry of 1)
1 0 0 0 1 0
i. Subtraction using 2’s complement:-
2’s complement = (1’s complement) + 1
Steps:- 1. Find the 2’s complement of the number to be
subtracted.
3. The complement which is arrived at 1st step is added to the
number from which it has to be subtracted.
4. If it results in a carry of 1, ignore that to obtain the result
5. If it results in no carry , add 0. Find the 2’s complement of the
result and attach a negative sign to obtain the required result.
Ex:- 10100 - 10110 using 2’s complement.
Sol:- Given number 0 1 0 0 1
+ 1
2”s Complement 0 1 0 1 0
Add 2’s complement to 10100
1 0 1 0 0
+ 0 1 0 1 0
1 1 1 1 0
0
1 1 1 1 0
1.7 Basic Input/Output Devices
These are those devices which facilitate a user to gives input, i.e. date to
the CPUto work on.
i) Punched Cards : These input units were used by Charles Babbage,
the “Father of Computers” These punched cards are rigid pieces of paper
which contain rows and columns of Numbers. These cards are kept ion a
punch machine, which makes holes in the cards to represent the data.
Punched card has the following advantages:
ii. It is relatively cheaper.
iii. Both user as well as machine can read data.
ii)Punched Paper Tape: This is a continuous strip of paper on which
the characters are represented by using a code which is made of
combination of circular holes punched across the width of the paper.
Advantages:i. As the paper tape is cheaper than punched cards
ii.The speed of paper tape reader being about 1100-
1000 characters per second.
v) Magnetic Tape: Magnetic tapes are made of thin plastic
coated with magnetic materials like iron oxide. It can
be magnet5ized in either of two direction. Magnetic tape
drive used to read and also to write data on the
magnetic tape. The speed of the magnetic tape drive is
about 5000to 2,40,000 characters per second.
Advantage of this tape is it can be reused.
vi) Video Display Unit (VDU):- These are also used as input
devices for computers. Are very similar to a picture tube
of television. These are also know as Cathode Ray
Tube.
vii) Key Boards:This is the most common and popular input device. It is similar
to the ordinary typewriter.
Key boards usually contain the following keys:-i) Numeric Keys
ii) Character keys
iii) Function keys
iv) Special keys
vi) Mouse: This input device is used specially for Graphic User
Interfaces(GUI). It contains one to three buttons.
This is used as a pointing device.
vii) Joy Stick: This is one of the popular input device, which is
used for playing video games.
viii) Touch Screen: Touch screen takes input as when a finger or
object cones in contact with the screen, the light beam is broken,
and the location of breaking of light beam is recorded, which acts
s inputs.
ix) Magnetic Ink Character Recognition: This MICR reader
reads the characters which are written using
special magnetic ink. These are also human readable.
Advantages like: Inspite of rough handling, one can read
the information with a very high degree of accuracy.
X) Magnetic Strips: These are thin bands of
magnetically encoded data. These are usually
sued on credit cards. The data cannot be
seen and read by mere looking at the card, there
here it is usually secret.
XI) Light Pen: Light is a type of pointing device that is used to
choose a displayed menu option on screen for a program. This
pen contains a photocell placed in a small tube.
XII) Voice Input Devices: These devices are in stage of
experimenting and development, where various problems
like speech should be independent of persons.
XIII) Optical Mark Reader: These devices use any of two methods,
one method relies on conductivity of graphite which determines
the presence of pencil mark, for this only soft pencil should be
used.
Output Devices: Output devices can adopt different shapes and styles,
which are used to give the output of the processing of data. The output
can be in any form i.e. typed, printed, sketched, visible, nonviable,
audio, video etc. Output devices are those peripheral devices that allow
a user to retrieve information from a computer. Any Output devices
can be devided in to two basic categories
1. Hard Copy 2. Soft Copy
1. Hard Copy : It is that form of output which can be read directly
and immediately, stored to be read later. This output is on paper
and which is permanent.
2. Soft Copy: It is magnetic or audio form of output which is usually
unreadable directly and which is not long-lasting.
Hard Copy Devices:- These are those devices, Which produce
permanent record of data on media like paper. These are relatively
slow in operation, when compared to soft copy devices. Some of the
popular devices are
a. Printers b..Plotters c.Photographic output devices d.Punched
cards.
a. Printers : Printers can be categorized in to
1. Impact Printers
2. Non-impact Printers
a. Impact Printers: These are those
type of printers which have direct
mechanical contact between the
head of the printers and paper. The
impact printers are
1.Dot Matrix Printers: - These Printers print characters as combination
of dots arranged in a 5 x 7 matrix. The speed of these printers vary from
about 30 to 600 characters per second. The printing head of these
printers contain vertical array of pins, which fires the selected pins against
carbon ribbon or linked surface, while the head moves across the paper
to form a pattern of dots representing characters. These printers can print
characters in draft quality, standard quality as well near letter quality.
b. Daisy Wheel Printers.:- This printer is a solid font type
character printer. The printing arms of the printer head look
like petals of the flower. This printer is very slow,it prints
about 60-90 characters per second. The hub rotates
continuously, rotating at high speed and hammer strikes
the appropriate character in its position. This printer is also
act as bi-directional printer .
c. Line Printers:- These printers which print total line at a
time, giving the name line printers. They can be print 1000-
5000 lines per minute.
Non -Impact Printers: - These printers print without any direct mechanical
contact between the head of the printer and paper. These printers can
categorized in to
a. Thermal b. Inkjet c. Laser d. Electrographic e. Electro Static
a. Thermal Printers:- These Printers uses heat sensitive paper in dot
matrix method, on which hot needles are pressed to form characters.
These printers print slow and makes little noise. The disadvantage is
that it is not possible to print multiple copies simultaneously.
b. Inkjet Printers:- These printer uses a mechanism where it sprays
the ink from tiny nozzles through an electric field that arranges
charged particles ink into characters. The paper absorbs the ink and
it dries instantaneously. It is capable to print about 500 cps , expensive
but faster and we can also have color printing, by using ink various
colors.
c. Laser Printer:- This type of printers uses laser beams which charge
the drum negatively, to which black toner powder which is positively
charged is sticked. When the paper rolls by the drum, the toner
powder is transferred to the paper. These printers are very fast, quality
is very good and speed about is 15,000 to 20,000 lines per minute.
d. Electrographic Printer:- This printer writes on special paper usinf
electricity. The paper is held between two electrodes. These printers
can either use wet process or dry process. The speed of these printers
are fairly high and is about 20,000 cps. These printers are very reliable
as there are very less moving parts.
e. Electro Static Printer:- This printer uses a mechanism, where static
electricity is used to create impressions on special paper. The
charges attract toner power to the charged spots, giving the print.
This printer s are very fast and are capable for plotting graphs etc.
The speed is very high i.e up to 20,000 lines per minute.
II. SOFT COPY DEVICES:- These devices output is usually not visible
directly but cab be viewed with help of computer where one can
update, modify data etc.
Some of the softcopy output devices are
a. Visual Disply Terminal :-
1. Dumb Terminal 2. Smart Terminal
3. Intelligent Terminal
b. Visual Display Unit (Monitor) : The screen of monitor is generally
two types.
i. Cathode Ray Tube: ii. Flat-panel Display
1.8 Memory Units
Basically Computer Memory is divided in to Primary Memory and
Secondary (Auxiliary) Memory
Primary Memory : - Which is purely temporary memory (i.e the data or
program lies in this memory till the program is executed or power is lost )
i.e volatile
Ex. RAM,ROM ,PROM,EPROM and EEPROM etc.
Secondary Memory : Which is non-volatile memory and which is
external to computer. It is a secondary media used for storing large volumes
of data permanently for long term.
The following are the secondary storage devices:-
1. Magnetic Tapes 2. Magnetic Disks 3. Optical Disks
1. Magnetic Tapes :- These are external storage devices which as used
as high speed input and output devices. These devices use a tape which is
about 12.5 mm to 25 mm wide and about 500meters long. This tape
made up of plastic like material known as mylar. This tape is wound on a
spool which can be loaded onto the tape deck. This deck is connected to
the CPU permanently and the information stored into or read from ,the
tape by the processor. This tape is coated with a very thin layer of iron
oxide, magnetic material.
These tapes are to be accessed serially . The data is stored as binary
digits i.e. one and zero are represented as presence and absence of
magnetic field. i.e. spots on the tape.
Advantages of using Magnetic tapes:-
1. Large amount of data can be stored in to small lengh of magnetic
tape
2. The Tape is very easy and convenient to handle.
3. The tape cost is very economical
4. It is very fast and life of the magnetic tape is very high, permitting
long term storage.
Magnetic Disks: - Magnetic disk is usually made up of plastic like
material called mylar or any metallic platter coated with ferromagnetic
material. The data is stored in the same way as magnetic tapes. Here
read/write heads are small electromagnets which are capable to read,
write or even erase the data stored as magnetic spots.
They can have varied storage capacities. These disks can be divided in
to1. Fixed or Hard Disks 2. Floppy disks.
1. Fixed or Hard disks:- Fixed or Hard disks is usually made from
aluminum or other materials instead of mylor or other plastic like
material. . Hard disk is permanently installed in the drive . This disk is
usually large(about14inches). These disks also come in various sizes
like 9inch,5inch etc.
2. Floppy disks: This new device used for secondary storage media,
this small ,flexible, faster and cheap alternative for the storage purpose.
This disk is made up of flexible plastic material, coated magnetic
materials like iron oxide. Data is recorded in the form of invisible
magnetic spots on coating. This floppy diskette comes in three basic
sizes are 8 inch,5.25 inch and 3.5 inches
4. To store data in the floppy it has to formatted i.e. the floppy surface
has to be divided in to tracks and sectors.
5. Tracks:- These are logical concentric circles which start from the edge
of the floppy disk and move inwards, towards the center of the disk.
The tracks are numbered.
6. Sectors:- The small portions of the tracks are called sectors where
the data is stored physically. The amount of data stored in a sector is
depends on the floppy disk. When the data is stored in a sector, if it
becomes fully, then it I stored in the nest sector. The floppies can
divided according to storage capacities.
1. 48 TPI- Double Sided -Double Density (DSDD)
ex: 5.25 inch- 360KB
2. 96 TPI- Double Sided-Double Density(DSDD) Ex:- 720 KB
3. 96 TPI- Double Sided-High Density(DSHD) Ex : - 1.2 MB
4. 135 TPI- Double Sided-High Density(DSHD) Ex:- 3.5 inch - 1.44MB
Advantages of Magnetic Disks:1. The magnetic disks provide for easy accessibility to the stored data.
The time takes for access is very less.
2. The disk has longer life then tapes.
3. We can access data both sequentially, or randomly
4. We can update several on line disk records by single input transaction
3. Optical Disks:- This Optical technology is capable storage devices
which can store large amount of data . This technology involves the
uses of laser beams, which are highly concentrated beams of light.
Using this technology several secondary storage devices can be
revolutionized by the use of the following secondary storage devices
based on optical technology.
1. Optical disk
2. Optical card
3. Optical tape
1. Optical disk:- This is similar to the laser-optical video disks which
are sold for home purpose. Optical disks use same technology for storing
data onto them. This disk is made of hard metal ranging from 4.72 inches
to14 inches in size. These disks were initially developed and used as
compact disks for video and audio applications. To store data laser beams
are used to burn the microscopic “pits” to represent binary digits i.e. 0’s
and 1’s. These pit patterns represent data. These disks are read using
optical disks drives that use beam of lasers to read pit patterns and convert
them in to bits.
These disks usually come as read only . These disks are usually used
to store programs, utilities, software, data etc. so that one can read the
contents and carry on required work. These are generally termed as CD
ROM’s.
Erasable Optical disks:- These are the disks which are erasable and
can be reused. These disks are bit expensive. We can use CD-writer to
write in to these CD’s.
II. Optical Card:- These are similar to credit cards in size and they
have an optical laser encoded strip. These cards can store about 2
MB of data. These cards can be used to storing credit records, also
can be used all cash transactions as well as cheque transactions.
III. Optical Tape:- This is similar to magnetic tape in looks, but it differs
that the data is stored using optical technology. These tapes come in
cassettes, can store 8GB. These tapes are read by using Optical
tape drives, These drives are capable le of holding about 128
cassettes.
1.9 Operating SystemsOperating System (OS) can be defined as “set of Programs that are
capable to manage resources as well as the operations of a computer”.
Operating system hides the hardware from the user.
The basic functions carried by the Operating system are:
1. Assigning processors for performing tasks.
2. Allocating and managing memory, and other storage area
3. Command interpretation
4. Handling job transactions.
5. Maintains internal clock
6. Scheduling of various tasks.
7. Establishing and enforcing priorities for different jobs.
8. Co-ordinating and managing peripheral devices.
9. Input-output management
10. Establishing data security and integrity.
Operating system concepts:- User programs interact with operating
system using set of extended instructions. These instructions are called
“system calls”. These system calls are used to create, delete and use
various software objects that are manages by the Operating systems. The
following are common in any Operating system.
1. Process
2. Files
3. System Calls
4. The shell
5. Booting Process i. Boot Strap Loader
i. Check Programs
ii. Monitor Program
iii. Basic input/output System(BIOS) Program
iv. Utility Programs
v. File Maintenance Programs
Types of Operating systems:- Operating systems are basically
capable to do all functions but The way of processing or approach of the
systems may vary from one Operating systems to another. The following
basic types of operating systems are
1. Batch Processing Systems
2. Interactive Operating systems
3. Multi-Programming Operating Systems
4. Multi-Processing Operating Systems
5. Multitasking systems
6. Multi-user Operating systems
7. Virtual storage systems
Basing on the features of the operating systems and the interface provided
they can be classified as
1. User friendly Operating system :- These Operating systems provide
a pleasant and easy to work environment, they are usually graphical
based, where the various options are represented as icons, menus
etc. Windows 95, Windows 98, Windows-NT are some of the user
friendly Operating systems.
2. Programming friendly Operating systems:- The programmer is
anyone who has fair knowledge about programming concepts and he
is expected to know the computer in a detailed manner. The
programmer much concerned about various utilities, functionlities,
flexibility and powerful environment. UNIX, XENIX,LINUX etc. are some
of the character
based interfaces which are very powerful and programming friendly.
Character User Interfaces( CUI):- This user interface is character based,
one gets prompts in characters and a user has to type the characters.
These were the interfaces which enabled the programmers to do work
easy, but they it is difficult to work in as we have to type every instruction
and commands . MS-DOS,UNIX,LINUX etc. are some of the most popular
character based operating systems.
Graphical user Interface(GUI):- This interface is graphical i.e. there are
pictures, graphical objects, images, menus etc . which have specific
functionality’s. This interface provides very pleasant environment to work
on it. Here almost every action is automated, at click of a button can get
desired action done. Windows95,Windows 98, Windows-NT are some of
very popular GUI based Operating systems.
Features of Operating Systems:- The major features of an Operating
System are
I . Processor Management
II. Device Management
III. Memory Management
IV . Security Management
V. File Management
H H H
INTRODUCTION TO PROBLEM SOLVING TECHNIQUES
2.1 ALGORITHMAlgorithm is a method of representing the step-by-step logical
procedure for solving a problem. An algorithm is a recipe for finding the
right-answer to a problem or to a difficult problem by breaking down the
problem into simple cases.
According to D.E. Knuth, a pioneer in the computer science
discipline, an algorithm must possess the following properties
(i) Finiteness : An algorithm must terminate in a finite number of
steps
(ii) Definiteness : Each step of the algorithm must be precisely
and unambiguously stated
(iii) Effectiveness : Each step must be effective, in the sense that
it should be primitive (easily convertable into program
statement) can be performed exactly in a finite amount of
time.
(iv) Generality : The algorithm must be complete in itself so that it
can be used to solve all problems of a specific type for any
input data.
(v) Input/Output : Each algorithm must take zero, one or more
quantities as input data produce one or more output values.
An algorithm can be written in English like sentences or in any
standard representation Sometimes, algorithm written in English like
languages are called Pseudo Code
Example :
1. Suppose we want to find the average of three numbers, the algorithm
is as follows
Step 1 Read the numbers a, b, c
Step 2 Compute the sum of a, b and c
Step 3 Divide the sum by 3
Step 4 Store the result in variable d
Step 5 Print the value of d
Step 6 End of the program
2. Find the average of n inputted numbers
Step 1 Read the total number of ovales,n
Step 2 Assign the value 9 to count (count = 0)
Step 3 Assign the value 0 to sum (sum = 0)
Step 4 If the value count is equal to the value n go to
the step 9 (if count = n go to step 9)
Step 5 Read the value, a
Step 6 Add the value of a to sum and store into sum
variable (sum = sum +a)
Step 7 Increment the value of count by 1 (count = count +1)
Step 8 Go to step 4
Step 9 Compute the division of sum and n and store
the result into avg variable (avg = sum / n)
Step 10 Print the value of avg
Step 11 End of program
The above algorithm terminates after some time, which explains
the property of finiteness. Action of each step is precisely defined. In this
example, each step requires simple operations such as reading, assigning,
comparing, printing and so on. This explains the feature of definiteness
and effectiveness. Total number of entries and their values will be the input
for the algorithm where as the average of the entered values will be the
output. Formally, an algorithm can be defined as an ordered sequence of
well-defined and effective operations that, when executed, will always
produce a result and eventually terminate in finite amount of time.
When a problem is to be solved or some complex task is to be
accomplished, the most natural way is to break the problem (or task) into
small problems, which can be solved easily. Consider a shopping example
where the task is to purchase the required items. This can be achieved by
doing the following tasks.
1.1 Going to the shop
1.2 Selecting and purchasing the required items
1.3 Returning back
Each of these tasks can be further divided into sub-tasks.
1.1.1 Go to the bus stop
1.1.2 Board the appropriate bus
1.1.3 Get the ticket
1.1.4 Reach the destination
