Unit 1: Introduction to
Computer System
Information Technology:
IT is the techniques used in
Information System. An information system collects, processes, stores,
analyzes, and disseminates information for a specific purpose. Communication is
the backbone of IT. IT can be defined as the implementation of Information
Science where Information Science is a set of algorithms, principles and
theories. Computer System, Internet, Telecommunication systems are the
information technology we use.
Information systems are
scattered throughout organizations, often in several locations and sometimes in
two or more organizations. IT is implemented here to relay the information
between these locations. Not only the organization but also the individual
today is dependant on IT for career development and education. Education
Institutions today provide distant education and online examinations. GIS has
emerged due to the development in IT. Scientists now are able to acquire
geographical information from the satellites.
Evolution of Information
Processing
Information Processing evolved
due to the growth of national and international organizations. Since the early
computing days, as costs declined and computer technologies improved, computers
have been used to support managerial and other organizational activities of
every sort.
Scopes/ Application field of
Information System
Telecommunication
Internet
GIS
Education
Security System
E-Governance
Medicine
Scientific Research
1.1 Introduction to
Computers
A computer is a programmable
electronic machine. It takes raw facts as input, process these and gives the
final output which is the result of processing. It responds to a specific set
of instructions in a well-defined manner. It can execute a prerecorded list of
instructions (a program).
1.2. Classification of
Digital Computers (Types of Computers)
Computers can be classified by
their size and power as follows:
1. Super Computers
2. Mainframe Computers
3. Mini Computers
4. Work Stations
5. Micro Computers/ Personal
Computer
a) Super Computers
They are the computers with
the most processing power.
• The primary application of
supercomputers has been in scientific and military work, but their use is
growing in business as their prices decreases.
• They are especially valuable
for large simulation models of real world phenomena, where complex mathematical
representations and calculations are required or for image creation and
processing.
• They are also used in weather
prediction, design aircraft( Boeing 777), motion picture like star wars and
Jurassic Park)
• They operate generally at 4
to 10 times faster than the next most powerful computer class., the mainframe.
a) Mainframe Computers
• They are less powerful and
generally less expensive than supercomputers.
• Large corporate use mainframe
computers for centralized data processing maintaining large databases.
•
• Application than run on a
mainframe can be large and complex, allowing for data and information to be
shared throughout the organization.
• Examples: Airline Reservation
System, Corporate Payroll, Student Information etc.
• A mainframe system may have
anywhere from 50megabytes to several gigabytes of primary storage.
• Secondary storage may use
high capacity magnetic and optical storage media with capacities in the
gigabytes to terabyte range.
• Typically, several hundreds
or thousands or online computers can be linked to a mainframe.
• Advance mainframe performs
more than 1,000 MIPS and can handle up to one billion transactions per day.
b) Mini Computers
• Also called midrange
computers, are relatively small, inexpensive and compact computers that perform
the same functions as mainframe computers but to limited extent.
• They are designed specially
for accomplishing specific tasks such as process control, scientific research,
and engineering applications.
• IBM is the market leader in
minicomputers with its AS/400 series of computers.
• Larger companies gain greater
corporate flexibility by distributing data processing with minicomputers in
organizations units instead of centralization at one place.
• They form the network.
c) Workstations
• Computers vendors originally
developed desktop engineering workstations or to provide the high levels of
performance demanded by engineers.
• They are based on RISC
(Reduced Instruction Set Computing) architecture and provide both very high
speed calculations and high resolution graphic displays.
• The distinction between workstation
and personal computers is rapidly blurring.
• The latest PC s has the
computing power of recent workstation.
d) Micro Computers
These are also called PCs and
are the smallest and least expensive category of general purpose computers.
Micro computer ranges from palmtops to Desktop computers. Laptops/ Notebooks
are very popular now a day. Microprocessor is the core part of the Micro
computers which forms the CPU.
1.3. Anatomy of Digital Computers
Functions and Components of
a Computer:
To function properly, the
computer needs both hardware and software. Hardware consists of the mechanical
and electronic devices, which we can see and touch. The different parts of the
computer are Processor (CPU), Input devices, Output devices, Storage devices
and Memory devices. The software consists of programs, the operating systems
and the data that reside in the memory and storage devices.
A computer does mainly the
following four functions:
v Receive
input – Accept information from outside through various input devices like the
keyboard, mouse, etc.
v Produce
information – Perform arithmetic or logical operations on the information.
v Produce
output – Communicate information to the outside word through output devices
like monitor, printer, etc.
v Store
information – Store the information in storage devices like hard disk, floppy
disks, etc.
Computer hardware falls into
two categories: processing hardware, which consists of the central processing
unit (CPU), and the peripheral devices. The CPU, as its name implies, is where
the data processing is done. Peripheral devices allow people to interact with
the CPU. Together, they make it possible to use the computer for a variety of
tasks.
Explain CPU and its
different components: CU, ALU and MU.
How CPU and memory does
works?
An instruction is fetched
from primary storage by the Control Unit
The Control Unit decodes the
instruction
The ALU receives the data and
the instruction and performs the calculation or comparison
The result is stored in
primary storage which is sent to the proper output device.
1.4. Computer Architecture
History: Describe from Pascaline to the first generation
computers:
Pascaline
In 1642, 19 year old French
mathematician Blaise pascal invented a mechanical adding-machine called
pascaline. The numbers were entered by means of add and subtract. It had 8
wheels and each wheel had 10 digits from 0 to 9.
Stepped Recknor
In 1671, German mathematician
Gothfried von Leibnitsz invented an improved and strong computing machine
called “stepped Recknor” which could multiply, divide and workout square roots
apart from addition and subtraction. The machine also had handle and gear.
Analytical Engine
In 1833, Charles Babbage,
(English mathematician) developed Analytical Engine which was a kind of a
general purpose computer designed to solve any arithmetical problems. It was
significant in a way that it had most of the elements present in today‟s
digital computer systems, that‟s why he‟s called “Father of modern computer
science.”
Lady
Ada Augusta, disciple of charles Babbage, after his demise developed several
programs for performing mathematical calculations on Analytical engine. She is
considered as the first programmer in history and has to her credit a computer
language called ADA named after her.
Dr. Herman Hollerith
In 1890AD, Herman Hollerith
designed a system to record census data. The information was stored as holes in
punched cards, which were interpreted by machines with electrical sensors.
Mark-I
In 1944 Howard Aiken completed
mark I. It was an electromechanical computer which was 51ft. long, 8 ft.
height, and 3 ft wide and consisted of 18000 vacuum tubes. This consisted of 7
lakh 50 thousand parts and 500 miles long wire.
Electronic Numerical integration
and calculator (ENIAC) – 1946 A.D.
ENIAC was the first electronic
computer developed by John Mauchly and John presper Eckret in 1946. It could do
5000 additions per second. It was extremely huge, used 19,000 vacuum tubes,
occupied an area of 150 sq. meters, weighed about 30 tons and required about
130 kW of power.
EDVAC:
In 1952, Electronic Discrete
Variable Automatic Computer (EDVAC) was developed by John Mauchly and John
Presper Eckert with the help of A. Burks and Neumann. This machine was used to
store the data and information as well as the instructions.
John Mauchly and Eckert
founded their own company in 1946 and began to work on Universal Automatic
Computer (UNIVAC): general purpose commercial computer in 1951. It was the
first commercially used electronic computer in the world.
In 1958, the first computer
to use the transistor as a switching device, the IBM 7090, was introduced.
In 1964, the first computer
to use Integrated circuits (IC), the IBM 360 was announced.
In 1975, the first
microcomputer, the Altair, was introduced. In the same year, the first
Supercomputer, the Cray-1 was announced.
RISC/ CISC
RISC (Reduced Instruction Set Computer) processors are
designed for speeding up the processing power of the computer making the chip
as simple as possible so that it uses less space and shorter design cycle. It
is possible to use the technique of pipelining using RISC processors which
gives the immense processing power.
The advantages of RISC
processors are as follows:
1.
Speed: Due to simplified instruction set RISC processors are 2 to 4 times
faster.
2.
Simpler hardware- Because of simpler instruction set the RISC processor uses
much less chip space, as a result extra functions are also placed in the same
chip.
3. Shorter design cycle-
Because of simple hardware and less instruction per task, the RISC processor
uses very short machine cycles.
CISC (Complex Instruction Set Computer) processors use
microcode, build rich instruction sets and build high-level instruction sets
and these were the building blocks until the late 1980s and are still in major
use today.
Some characteristics are:
1.
Complex instruction-decoding logic, driven by the need for a single instruction
to support multiple addressing modes.
2.
A small number of general purpose registers.
3. Several special purposes
register.
Advantages
of CISC:
1.
Microprogramming is as easy as assembly language to implement, and much less
expensive than hardwiring a control unit.
2.
The ease of micro-coding new instructions allowed the designers to make CISC
machines upwardly compatible, i.e. a new computer could run the same programs
as earlier computers.
3.
As each instruction became more capable, fewer instructions could be used to
implement a given task.
4. Because micro-program
instruction sets can be written to match the constructs of high-level
languages, the compiler does not have to be complicated.
The disadvantages of CISC:
1.
The instruction set and chip hardware became more complex with each generation
of computers.
2.
The instructions set were lengthy and took more time to execute, slowing down
the overall performance of the machine.
3. Many specialized
instructions aren‟t used frequently enough to justify their existence.
1.5. Number System
Refer to the exercise covered
during the class. Binary Subtraction using complement‟s method is left for
further discussion later after the Final Evaluation exam.
Memory Units:
Memory units are the internal
storages areas in a computer. These are in the form of chips. Usually we
classify the computer‟s memory into two categories: RAM and ROM.
RAM (Random Access Memory):
This is the main memory of the
computer. This is also found in other devices like printers. This memory holds
data as long as the electricity is supplied and therefore referred to as
volatile memory. There are two basic types of RAM: (i) Dynamic RAM (DRAM) and
(ii) Static RAM (SRAM).
Dynamic RAM needs to be
refreshed thousands of times per second. Static RAM needs to be refreshed less
often, which makes it faster; but it is more expensive than dynamic RAM.
ROM (Read Only Memory)
It is a non-volatile memory.
The data is prerecorded in ROM. The program stored in ROM is known as Firmware
and is programmed by the manufacturer. Once data has been written onto a ROM
chip, it cannot be removed and can only be read. Most personal computers
contain a small amount of ROM that stores critical programs such as the program
that boots the computer.
1.6. Auxiliary Storage Units
Hard Disk:
• A Hard disk is internal
hardware which stores and provides access to large amounts of information.
• Hard disks have much greater
data capacity and are much faster to use than floppy disks.
• Usually, it is a fixed disk,
permanently sealed in the drive.
• Most new computers include an
internal hard disk that contains several gigabytes or terabytes of storage
capacity.
• The head of hard disk that
reads the data floats over the hard disk‟s surface, while the head of the
floppy disk touches the disk‟s surface while reading or writing data.
• Hard disk is a flat, circular,
rigid plate with a magnetizable surface on one or both sides of which data can
be stored.
• Hard disks are rigid aluminum
or glass disks about 3.5” in diameter in a personal computer, and smaller in a
laptop.
• Data is transferred
magnetically by a read/write head.
• A hard disk is made of
metallic disk coated with metallic oxide on both sides.
• To increase the storing
capacity, several disks (platter) are packed together and mounted on a common
drive to form a disk pack.
• A hard disk can have more
than 1000 tracks per surface and contain 17 sectors per track.
Optical Disk
• An emerging technology that
many expect will have a profound impact on mass storage strategies in the 1990s
is the Optical Disk.
• With this technology becomes
laser beams to wrote and read data at incredible densities.
• Thousand of times finer than
the density of a typical magnetic disk.
• Data are placed onto optical
disks with high-intensity laser beams that burn tiny holes into the disk‟s
surface.
• Optical disk systems have
recently started to become widely used on microcomputer systems.
• So, it is a storage medium
from which data is read and to which it is written by lasers. Store much more
data in portable magnetic media.
• There are three basic types
of optical disks.
• CD-ROM (compact disk read
only memory)
• WORM ( write once read many)
• ERASABLE
• These three are not
compatible with one another.
• WORM (Write-one Read-many)
• With a WORD disk, you can
write data, but only once and then you can read number of times.
• ERASABLE Optical (rewritable
& erasable)
• Can be read to, written to
and erased just like magnetic disk.
• CD-R (Compact Disk
Recordable)
• CD-RD (Compact Disk
Rewritable)
• DVD (Digital Versatile Disc)
• Initial storage capacity of
4.7GB digital information on a single sided, single layer.
• Diameter & thickness is
same as CD-ROM.
Magnetic Tape:
• Magnetic tape is a plastic
tape with a magnetic surface for storing data as a series of magnetic spots.
• Magnetic tape has been one of
the most prominent secondary storage alternatives.
• Magnetic tape is the most
commonly used sequential access secondary storage medium.
• It is available in the form
of cassettes, real & cartridges.
• Among these three, Reels are
the most popular storage secondary media.
• Magnetic tape is a plastic
ribbon coated on one side with iron oxide that can be magnetized
Floppy Disk:
Floppy disk is a soft magnetic
disk. Floppy disks are being replaced by pen drives now a days. Foppy disks are
slower to access than hard disks and have very less storage capacity.
1.7. Input Devices
How does a Keyboard Work
Layout
Computer keyboards are an input device. They put the
information a person types into a program on the computer. Most keyboards have
80 to 110 keys. The numbers and letters on the keyboard are displayed
keycaps--these are the buttons that are pressed when a person types. The layout
of the numbers and letters are the same on every keyboard and they are referred
to as the QWERTY.
Key matrix
The inside of the keyboard is like a mini-computer and
consists of a processor and circuits.
These transfer the information to the processor inside
of the computer. Inside of the keyboard's processor resides the key matrix.
The key matrix is a grid of circuits. These circuits
are individually placed under each key. When a key is pushed, it pushes the
switch on the circuit board underneath the key causing an electrical current to
pass through the circuit and into the processor.
When the current passes through, the switch vibrates,
signaling the processor to read it.
Depending upon the working principle, there are two
main types of keys, namely, capacitive and hard-contact
Capacitive Key
On the underside of a capacitive key, a metal plunger
is fixed which helps in activating the circuit flow. When a capacitive key is
pressed, the metal plunger applies a gentle pressure to the circuit board. The
pressure is identified by the computer and the circuit flow is initiated,
resulting in the transfer of information from the circuit to the currently
installed software.
Hard Contact Key
A hard contact key is attached with a metallic plate
that helps in connecting the circuit board. When the hard contact key is
pressed, it pushes a metallic plate, which in turn touches the metallic portion
of the circuit plate. This overall process of completing a circuit results in a
circuit flow, allowing the transfer of the message to the central processing
unit (CPU), which is further transmitted to the software.
Working principles of mouse
The
mouse is a pointing device which helps us to operate the computer. Unlike the
complicated hardwares such as Mother board, RAM, Hard disk, Processor of the
computer, the mouse is designed with a simple circuit to process. Now a days,
we get varieties of mouse with different technologies in the market. In recent
days, the optical mouse had overcome the old ball mouse, because of its 'easy
to use' function.
§ The
main components of the optical mouse are:
Ø Inbuilt
optical sensor
Ø High speed
camera which can take 1000 pictures at a time
Ø LED
§ These
optical mouses do have an inbuilt optical sensor. The optical sensor reads the
movements of the optical mouse (moved by the user) with the help of the light
rays which comes out from the bottom.
§ When
the user moves the optical mouse, the LED (Light Emitting Diode) present inside
the mouse emits the light according the minute movements.
§ These
movements are send to the camera as light rays.
§ The
camera captures the difference in light rays as images. When the camera
captures the images, each and every pictures and compared to one another with
the digital technology.
§ With
the comparison, the speed of the mouse and the direction of the movement of the
mouse are rapidly calculated. According to the calculation, the pointer moves
on the screen.
Working principles of
scanner
§ The
basic principle of a scanner is to analyze an image and process it in some way.
§ Image
and text capture (optical character recognition or OCR) allow to save
information to a file on user computer.
§ user
can then alter or enhance the image, print it out or use it on their Web page.
Types of Scanners:
1.
Flatbed Scanners
2. Hand Held Scanners
How a Flatbed Scanner Works
A light source underneath the picture or document
illuminates the image. Spaces white or blank reflect more light than do inked
and colored areas.
A motor moves the scan head underneath the page. when
the scan head is moving it captures light that was reflected from individual
areas of the page about 1/90,000 of an inch
Light from this page is bounced through an intricate
system of mirrors that must continually pivot to keep the light beams aligned
with a lens.
A lens focuses the beams of light into light sensitive
diodes that translate the amount of light into an electric current. The amount
of the current depends on the amount of light reflected, the greater the amount
of light reflected the greater the current.
The analog to digital (A-D) converter stores each
analog reading of voltage as a digital pixel representing either a black or
white area. Scanners that are more sophisticated can translate the voltage into
shades of gray. In a color scanner, the scan head makes 3 passes under the
image and the light on each pass is directed through a red, green or blue
filter before it strikes the original image.
The digital information is sent to the pc where it is
translated into a format that a graphics program can read.
1.8. Output Devices
An output device is any
piece of computer hardware equipment used to communicate the results of data
processing carried out by an information processing system to the outside
world. Outputs are the signals or data sent by the system to the outside.
Examples of output devices:
Speakers
Headphones
Plotters
Printer
Plotters
A plotter is a graphics printer
that uses a pen or pencil to draw images. Plotters use continuous lines to
create images. Plotters are connected to computers and are used to produce
complex images and text. However, plotters are much slower than printers
because of the mechanical .
motion
necessary to draw detailed graphics using continuous lines. Architects and
product designers use plotters for technical drawings and computer-aided design
purposes since plotters have the ability to create large images on oversized
sheets of paper.
Printer
A printer is a peripheral which
produces a text and/or graphics of documents stored in electronic form, usually
on physical print media such as paper or transparencies. Many printers are
primarily used as local peripherals and are attached by a printer cable or in
most new printers, a USB cable to a computer which serves as a document source.
Some printers, commonly known as network printers, have built-in network
interfaces, typically wireless and/or Ethernet based, and can serve as a hard
copy device for any user on the network. Individual printers are often designed
to support both local and network connected users at the same time.
Types of printers
1. Impact type
2. Non-impact type
Impact Type
To create text or image by
physically make the print head to press the ink ribbon and cause the ink
deposition on the paper in desired form is called impact type. Normally it is
quite louder in nature when compared to other types of printers. The well-known
example for impact type is Dot Matrix and Daisy wheel. Some of the latest
impact based in the market is Line printer (high speed impact printer), IBM
electromagnetic table printing machine.
Non-Impact Type
This produce text or images on
paper without striking the paper physically are called as non-impact type.
These are not louder when compared to other types of printers. The well-known
example of this type is Thermal printer, lasers and inkjets
inkjet matrix
printers
Inkjet printer sprays tiny
droplets of ink onto the paper. Inkjet printer does not physically touch the
paper.
A print head scans the page in
horizontal stripes, using the printer's motor assembly to move it from left to
right and back again, while the paper is rolled up in vertical steps, again by
the printer.
A strip (or row) of the image
is printed, then the paper moves on, ready for the next strip. To speed things
up, the print head doesn‟t print just a single row of pixels in each pass, but
a vertical row of pixels at a time.
Inkjet printers‟ print head
takes about half a second to print the strip across a page.
Inkjet printer offers speed of
2-4 pages per minute (ppm).
Inkjet printers are inexpensive
and low operating cost.
Laser printer
Laser printer is a non-impact
high-resolution printer which uses a rotating disk to reflect laser beams to form
an electrostatic image on a selenium imaging drum. The developer drum transfers
toner from the toner bin to the charged areas of the imaging drum, which then
transfers it onto the paper into which it is fused by heat. Toner is dry ink
powder, generally a plastic heat-sensitive polymer.
Laser printers using chemical
photo reproduction techniques can produce resolutions of up to 2400 DPI.
The photoconductive drum is
given a positive or negative charge by the charge Corona wire.
When the drum starts to
revolve, a laser beam is shone on it. This laser beam consists of light
photons. The laser assembly shines the laser beam on a mirror which is then
reflected off the mirror. As a result, the drum that is made up of
photoconductive material is discharged.
The areas of the drum that
are touched by the laser develop charge that is opposite to the charge of the
drum.
The laser etches figures and
characters on the surface of the photoconductive drum. The figures or
characters are actually a pattern of electric charges. In this case let us
assume that the drum is positively charges. Therefore, the laser etched areas
will be negatively charged.
Thereafter, a fine ink powder
called toner is sprinkled on the paper. This powder has to be positively charged.
As the drum rolls, the toner
adheres to the laser-etched area of the drum. It is repelled from the
positively charged area of the drum. Thus, the laser pattern is etched on the
drum with the toner.
After this, the drum rolls
over the paper. The paper passes along a belt under the drum.
The paper is given a negative
e charge. This negative charge must be stronger than the charge of the
laser-etched electric image. This will aid the toner to leave the negative area
on the drum for the negatively charged paper.
The paper is discharged as it
moves out. This will prevent the paper from getting attached to the positively
charged drum. The paper moves at the same speed as the drum.
The paper is passed through a
fuse. As the paper passes through a fuser, the toner melts due to hear. The
tone is thus fixed on the paper.
The fuser rolls out the paper
to the output tray. The printing process of a laser printer is thus complete.
Projector
A projector is a device that
uses light and lenses to take an image and project a magnified image onto a
larger screen or wall. Projectors can magnify still or moving images depending
on how they are built. The image must be shone through a sealed tube or frame
when passing through the lenses to maintain focus.
The video projector contains LCD panel.
At the centre of projector is a halogen bulb which is surrounded by panel.
The panel produce light. As
the halogen bulb heat up the crystal melt and allow more light to pass through.
Hence the intensity of halogen bulb brings about the difference in tones.
Higher the temperature of
bulb lighters the tone.
Images travel to the tube
present inside the projector from DVD player or satellite box.
These images are turned bound
on a screen that is coated with phosphorus. Every fragment of light hitting the
screen is termed as pixel.
On heating the screen the
pixel break down into its colour components i.e. red, green and blue.
The heat produce by halogen,
bulb is controlled by voltage that flow into LCD video projector.
Advantages of projector
1.
Produce sharper images.
2.
They have an edge in light efficiency.
3.
They generate largest possible image size.
4.
Low cost.
5. Space saving.
Disadvantages of projector
1.
Image quality may not be as good as projected.
2.
Dark room often required.
3.
Maintenance required.
4. The pixel on the chip can
burn out. When one pixel burn out the whole chip will have to replace.
Unit 2: Computer Software and Software Development
2.1. Software
Software is a collection of set of programs, which are
used to execute all kinds of specific instruction. It consists of a number of
machine instructions, array in a specific order to perform a particular task.
Software is used to describe all the programs and its associated documents
which run on a computer. So, a computer needs both software and hardware for
its proper functioning.
Software means computer instructions or data. Anything
that can be stored electronically is software.
Firmware are software (programs or data) that has been
permanently written onto read-only memory (ROM)
.
All software falls into two general types or
categories: System Software and Application Software. System software
consists of low-level programs that interact with the computer at very basic
level. This includes operating systems, compilers, and utilities for managing
resources. On the other hand, application software includes database programs,
word processors, and spreadsheets.
Examples of System software
are as follows:
a) Operating Systems
Operating systems are the most
important programs that run on a computer. Every general-purpose computer must
have an operating system to run other programs. Operating systems perform basic
tasks, such as recognizing input from the keyboard, sending output to the
display screen, keeping tracks of files and directories on the disk and
controlling peripheral devices such as disk drives and printers. Most commonly
used operating systems include Microsoft Windows, DOS, Xenix, Mac OS, OS/2,
UNIX, MVS, etc.
b) Compilers and
Interpreters
Compiler is a program that
translates source code into object code. The compiler takes the entire piece of
source code and collects and recognizes the instructions. In contrast, the interpreter
analyzes and executes each line of source code in succession, without looking
at the entire program. The advantage of interpreters is that they can execute a
program immediately but compilers require some time before an executable
program emerges. However, programs produced by compilers run much faster than
the same programs executed by an interpreter.
c) Device Drivers
Device drivers are the software
to run the particular peripheral devices like printers, wireless mouse, modems,
and Ethernet cards etc. Most of the peripheral devices attached with the CPU
needs device drivers to carry out the functions. Mostly we get device drivers
at the time of buying these devices. For example we get the printer driver when
we buy the printer. Device driver lets the CPU know the type of hardware and
the type of instruction for a particular device attached with it.
Examples of Application Software are as follows:
a) Word Processors
A word processor is a program
that makes us possible to perform word processing functions. We can create,
edit, and print documents using word processors. We have many features that
help us to prepare a fine document. Some of the important features of word
processors are: editing, spelling checking, page setup, paragraph alignments,
merging documents, typing in columns etc.
MS-Word is the word's most
popular word-processor. Although every word processor provides almost the same
features, MS-Word is most flexible to work with. It is used to write documents
or letter. A file in Ms-Word is called a document. When a file is saved,
MS-Word attaches the extension .doc to the file.
b) Spreadsheets
A spreadsheet is a table of
values arranged in rows and columns. Each value can have a predefined
relationship to the other values. If one value is changed, others values need
to be changed as well.
Spreadsheet applications are
computer programs that let you create and manipulate spreadsheets
electronically. In a spreadsheet application, each value sits in a cell. We can
define what type of data is in each cell and how different cells depend on one
another. The relationships between cells are called formulas, and the names of
the cells are called labels. Once we have defined the cells and the formulas
for linking them together, we can enter the data. We can then modify selected
values to see how all the other values change accordingly. What-if analysis
makes the complex decision-making a very easy process. MS-Excel is one of the
most popular spreadsheet applications.
c) Multimedia applications
Multimedia applications make us
possible to run audio and video files. This application recognizes the digital
signals and provides necessary signal to output devices and movie signals to
the monitor and audio to the audio devices. Along with the video data we also
get the text information about the file we are running. In windows operating
system Windows Media Player is a good option to play the multimedia files.
d) Presentation Graphics
Presentation Graphics enable
users to create highly stylized images for slide shows and reports. The
software includes functions for creating various types of charts and graphs and
for inserting text in variety of fonts. Most systems enable us to import data
from a spreadsheet application to create the charts and graphs. Presentation
graphics is often called business graphics. Some of the popular presentation
graphics software are Microsoft PowerPoint, Lotus Freelance Graphics, Harvard
Presentation Graphics, etc.
Utility Software
Utility is a program that
performs a very specific task, usually related to managing system resources.
Antivirus software, Disk Partition tools are the examples of utility software.
2.2. Operating System
OS is an important system
software package found in every computer systems. It is a set of programs that
controls and supervises a computer system‟s hardware and it provides services
to computer users. It permits the computer to supervise its own operations by
automatically calling in application programs and managing data needed to
produce the output desired by users. OS is an interface between the user and
the computer. OS perform basic tasks, such as recognizing input from the
keyboard, sending output to the display screen, keeping track of files and
directories on the disk, and controlling peripheral devices such as disk drives
and printers. OS, as a resource manager keeps track of who is using which
resource, to grant resource requests, to account for usage and to mediate
conflicting requests from different programs and users.
Functions of an Operating
System:
Job Management: OS manages the jobs waiting to be processed. It
recognizes the jobs, identifies their priorities, determines whether the
appropriate main memory and secondary storage capability they require is
available, and schedules and finally runs each job at the appropriate moment.
Batch Processing: Data are accumulated and processed in groups. The
printing tasks in the printer are also done in groups. Most of the tasks of OS
are grouped and performed one by one.
On-line Processing: In on-line processing, data are processed
instantaneously. Most on-line operating systems have multi-user and
multitasking capabilities. Now a day we can access the data from the remote
sites using on-line processing.
Data Management: OS manages the storage and retrieval of data. As the
system software handles many of the details associated with this process, such
details are not a primary concern for users or programmers writing application
programs.
Virtual Storage: Using this method the capacity of main memory
increases without actually increasing its size. This is done by breaking a job
into sequences of instructions, called pages or segments, and keeping only a
few of these in main memory at a time; the remaining are kept on secondary
storage devices. Thus, relatively large jobs can be processed by a CPU.
Input/ Output Management: OS manages the input to and output from a computer
system. This applies to the flow of data among computers, terminals, and other
devices such as printers. Application programs used the operating system
extensively to handle input and output devices as needed.
Function of operating system
can be further listed as follows:
user interface implementation
share hardware implementation
Allows users to share data.
Prevent users from
interfering with one another.
Scheduling resources among
users.
Facilitate input/output
Facilitate parallel
operations
Organize data for secure and
rapid access.
Handle network communications
Classification of Operating
System:
Multi-user: These systems allow two or more users to run programs
at the same time. Some OS permit hundreds or even thousands of concurrent
users. The operating systems of mainframes and minicomputer are multi-user
systems. Examples are MVS, UNIX, etc. Another term for multi-user is
time-sharing.
Multiprocessing: It refers to a computer system‟s ability to support
more than one process (program) at the same time. This system allows the
simultaneous execution of programs on a computer that has several CPUs.
Mainframe, Supercomputers have more than one CPU.
Multitasking: This system allows a single CPU to execute what
appears to be more than one program at the same time when, in fact, only one
program is being executed. In multitasking, only one CPU is involved, but it
switches from one program to another so quickly that it gives the appearance of
executing all of the programs at the same time.
Multithreading: Multithreading allows different parts of a single
program to run concurrently. Multithreading is the ability of an OS to execute
different parts of a program, called threads, simultaneously.
Real-time: These operating systems are system that responds to
input immediately. It allows a computer to control or monitor tasks performed
by other machines and people by responding to the input data in the required
amount of time.
2.3. Programming Languages
Programming Language is a set
of rules that provides a way of instructing the computer to perform certain
operations. Programming languages are said to be lower or higher, depending on
whether they are closer to the language the computer itself uses or to the
language that people uses.
We can study the programming
languages under five levels (or generations) of language:
1.
Machine Languages / First generation Languages
2.
Assembly languages / 2nd Generation Languages
3.
Procedural Languages/ Third-generation Languages
4.
Problem-oriented Languages / Fourth generation Languages
5. Natural Languages / Fifth
Generation Languages.
