Unit - 2

redlemonbalmMobile - Wireless

Dec 10, 2013 (3 years and 8 months ago)

83 views


1

Unit
-

2

Computer Software

Computer Software

:

Computer software
, or

software

is a general term used to describe a collection
of computer programs, procedures and documentation that perform some tasks on a
computer system

The term includes
application sof
tware

such as word processors which perform
productive tasks for users,
system software

such as operating systems, which interface
with hardware to provide the necessary services for application software, and
middleware

which controls and co
-
ordinates dist
ributed systems.

Software includes websites, programs, video games etc. that are coded by programming
languages like C, C++, etc.

"Software" is sometimes used in a broader context to mean anything which is not
hardware but which is
used

with hardware, suc
h as film, tapes and records.

TYPES OF SOFTWARE

C
omputer systems divide software systems into
two
major classes:

i.

S
ystem software

ii.

A
pplication software
.

1.
System software

System software

helps run the computer hardware and computer system. It
includes operat
ing systems, device drivers, diagnostic tools, servers, windowing systems,
utilities and more.

The purpose of systems software is to insulate the applications programmer as
much as possible from the details of the particular computer complex being used,
e
specially memory and other hardware features, and such as accessory devices as
communications, printers, readers, displays, keyboards, etc.


2


O
perati
ng system

An operating system (commonly abbreviated
OS

and
O/S
) is the software
component of a computer system that is responsible for the management and coordination
of activities and the sharing of the resources of the computer. The operating system acts

as a host for applications that are run on the machine. As a host, one of the purposes of an
operating system is to handle the details of the operation of the hardware. This relieves
application programs from having to manage these details and makes it ea
sier to write
applications

D
evice driver

In computing, a device driver or software driver is a computer program allowing
server
higher
-
level computer programs to interact with a hardware device.



S
erver

A

server

is a computer dedicated to providing one or

more services over a
computer network, typically through a request
-
response routine. These services are
furnished by specialized server applications, which are computer programs designed to
handle multiple concurrent requests
.


Examples of server applicat
ions include mail servers, file servers, web servers,
and proxy servers.


3


Utility software

Utility software (also known as
service program
,
service routine
,
tool
, or
utility
routine
) is a type of computer software. It is specifically designed to help manag
e and
tune the computer hardware, operating system or application software, and perform a
single task or a small range of tasks; as opposed to application software which tend to be
software suites. Utility software has long been integrated into most major
operating
systems.


2.
Application software


Application software allows end users to accomplish one or more specific (non
-
computer related) tasks. Typical applications include industrial automation, business
software, educational software, medical software
, databases, and computer games.
Businesses are probably the biggest users of application software, but almost every field
of human activity now uses some form of application software.


Types of Application Software:

Word Processing Software
: Allows users

to create, edit a document


Example: MS Word, Word Pad etc.

Spreadsheet Software
: Allows users to create document and perform calculation.
Example: Excel, Lotus1
-
2
-
3 etc.

Database Software
: Allows users to store and retrieve vast amount of data. Example:
MS Access, MySQL, Oracle etc.

Presentation Graphic Software
: Allows users to create visual presentation. Example:
MS Power Point

Multimedia Software:

Allows users to create image, audio, video etc. Example: Real
Player, Media Player etc.




4

SOFTWARE DEVELOP
MENT STEPS:

Planning

The important task in creating a software product is extracting the
requirements

or
requirements analysis
. Customers typically have an abstract idea of what they want as an
end result, but not what software should do. Incomplete, ambiguous, or even
contradictory requirements are recognized by skilled and experienced softw
are engineers
at this point. Frequently demonstrating live code may help reduce the risk that the
requirements are incorrect.

Once the general requirements are gleaned from the client, an analysis of the scope of the
development should be determined and cl
early stated. This is often called a scope
document. Certain functionality may be out of scope of the project as a function of cost
or as a result of unclear requirements at the start of development. If the development is
done externally, this document can

be considered a legal document so that if there are
ever disputes, any ambiguity of what was promised to the client can be clarified.

Design

Domain Analysis

is often the fir
st step in attempting to design a new piece of software,
whether it be an addition to an existing software, a new application, a new subsystem or a
whole new system. Assuming that the developers (including the
analysts
) are not
sufficiently knowledgeable in the subject area of the new software, the first task is to
investigate the so
-
called "domain" of the software. The more knowledgeable they are
about the domain already, t
he less work required. Another objective of this work is to
make the analysts, who will later try to elicit and gather the requirements from the area
experts, speak with them in the domain's own terminology, facilitating a better
understanding of what is b
eing said by these experts. If the analyst does not use the
proper terminology it is likely that they will not be taken seriously, thus this phase is an
important prelude to extracting and gathering the requirements.



5

Specification

Specification

is the task of precisely describing the software to be written, possibly in a
rigorous way. In practice, most successful specifications are written to understand and
fine
-
tune applications that were already well
-
developed, although safety
-
critical software
systems are often carefully specified prior to application development.
Specifications are
most important for external interfaces that must remain stable.

A good way to d
etermine
whether the specifications are sufficiently precise is to have a third party review the
documents making sure that the requirements and
Use Cases

are logically sound.

Architectu
re

The architecture of a software system or
software architecture

refers to an abstract
representation of that system. Architecture is concerned with making sure
the software
system will meet the requirements of the product, as well as ensuring that future
requirements can be addressed. The architecture step also addresses interfaces between
the software system and other software products, as well as the underlying

hardware or
the host operating system.

Implementation, testing and documenting


Implementation

is the part of the process where
software engineers

actually
program

the code for the project.

Software testing

is an integral and important part of the software development process.
This part of the process ensures that
bugs

are recog
nized as early as possible.

Documenting

the internal design of software for the purpose of future maintenance and
enhancement is done throughout development. Th
is may also include the authoring of an
API
, be it external or internal.




6

Deployment and maintenance

Deploym
ent

starts after the code is appropriately tested, is approved for
release

and sold
or otherwise distributed into a production environment.

Software Training and Support

is important because a large percentage of software
projects fail because the developers fail to realize that it doesn't matter how much time
and planning a development te
am puts into creating software if nobody in an organization
ends up using it. People are often resistant to change and avoid venturing into an
unfamiliar area, so as a part of the deployment phase, it is very important to have training
classes for new clie
nts of your software.

Maintenance

and enhancing software to cope with newly discovered
pr
oblems

or new
requirements can take far more time than the initial development of the software. It may
be necessary to add code that does not fit the original design to correct an unforeseen
problem or it may be that a customer is requesting more function
ality and code can be
added to accommodate their requests. It is during this phase that customer calls come in
and you see whether your testing was extensive enough to uncover the problems before
customers do. If the labor cost of the maintenance phase exc
eeds 25% of the prior
-
phases'
labor cost, then it is likely that the overall quality, of at least one prior phase, is poor. In
that case, management should consider the option of rebuilding the system (or portions)
before maintenance cost is out of control
.

Bug Tracking System

tools are often deployed at this stage of the process to allow
development teams to interface with customer/field teams testing the software to
identify
any real or perceived issues. These software tools, both open source and commercially
licensed, provide a customizable process to acquire, review, acknowledge, and respond to
reported issues






7

INTERNET EVOLUTION




First experiments in 1966

ARP
A requested quotations in 1968

Packet switching was widely doubted, but was desired for its fault tolerance. One
objective was to build a system that could withstand any systematic attack on central
nodes, such as from a nuclear strike.

(The van Johnson st
ory)

AT&T was particularly pessimistic!

4 computers on ARPANET in 1969


8

in 1973 an effort began to connect ARPANET with mobile networks using synchronous
satellites (SATNET) and mobile packet radio (PRNET), this effort became known as
internetting

Part of t
his research effort resulted in Ethernet (in Hawaii)

July 1977 a four
-
network demonstration linked ARPANET, SATNET, and the PRNET.
TCP/IP version 4 came in 1978.

the new internet protocols, generally called TCP/IP, began to be developed in the early
70s, a
nd ARPANET switched to them in January 1983

supercomputer centers programmed in 1986 (Senator Goreĺs legislation) led to the
NFSNET, which remained the backbone until April 1995

experimental electronic mail relay put into operation in 1989, interconnecting

MCI Mail
with the Internet. Compuserve, ATTMail, and Sprintmail followed shortly

Principal Functions



e
-
mail



hobbies



news



personal publishing



product information



software distribution



commerce



telephony

According to (ftp://ftp.nw.com/zone), in january 96 t
here were 9.5 million hosts. Growth
rate is 20% per quarter.

Quantitatively, the success of the Internet is obvious. Less obvious is that the growth has
been fairly stableThe WWW was conceived by Tim Berners
-
Lee in March 1989, in a

9

CERN proposal. It first
aimed at managing information about accelerators and
experiments at CERN.

The concept of ôwebö derived from an observation of how new staff at CERN were
introduced to the work structure
-

by being given a few hints on who to talk to. At CERN
there is and w
as a large turnover, several thousand people are involved yet seldom stay
longer than 2 years.

Also improves on problems with hierarchical data structures (such as file systems) and
keyword based systems (such as bibliographic databases).

Other than using
TCP/IP, a key idea is a uniform naming scheme that includes the service
name. Also, in HTTP the client can send a list of the representations it understands, and
the server reply appropriately.

NCSA Mosaic came in 1992, and was instantly popular. Netscape
Communications was
formed in 1994.

There is not really any new technology in the Web concept, just a good combination of
ideas.

Matthew Gray used the first web ôspiderö, that he wrote in the spring of 1993, to locate
as many web servers as possible.

Today
there are over internetwork 600000 web servers (january 1997), according to
Netcraft.

The dotted Lines are my own estimates based on Netcraft and Internet society data.







10

Basic Internet Terminologies

:

Internet

-

Network of millions of computers used to

send information back and forth to
one another. There is no authority agency or company that decides what can and cannot
be published on the internet. This means that virtually anyone can publish, and means
that there are large
numbers

of sites that conta
in false and misleading information. It is
important to check who takes credit for the site you are viewing.

Homepage

-

Default setting, or the page that opens up when you start your Browser. A
homepage can also be the entry point for people viewing inform
ation that is provided.

Links

-

Hypertext which, when clicked, connects you to another site or another page
within the same site. In most cases, these links are usually highlighted in blue and are
always underlined.

Page

-

What is on your screen at any g
iven time. The page includes all the information
available to you by scrolling up or down; however, when you click on hypertext your
computer will 'jump' to a new page.

Search

Engines

-

Software that allows you to search the Web by typing in a topic of
in
terest.


Examples of search engines we use are Google, HotBot, and Northern Light. These
search engines find exact matches from what has been typed in the search screen to either
documents (files) or subjects of files on the WWW.

URL or Uniform Resource Lo
cator

-

The address for a specific file on the web, as well
as a method for directing users to a specific file, at a specific site. To type in a different
URL, press command and L at the same time on a Macintosh computer, control and L on
a PC, or locate t
he address bar at the top of the screen, type in the URL, and then press
return. The URL for the Blaine School District Home page is:
http://www.blaine.k12.wa.us.

Web Browser

-

To access the WWW, you need a Browser. A Web Browser is client
software that g
ets information from a server. It interprets the information, formats it, and
displays it on your computer screen. The most popular browser, and the one we use most
often in Blaine, is Internet Explorer.

WWW, World Wide Web or Web

-

Interactive collection

of hypertext pages linked to
one another. They may include text, graphics and/or links to other spots in the Web. The

11

Web is interactive because a user can click on text or graphics to navigate (move) to more
information or other graphics, sounds and vide
o that is of interest to them.


Home page

-

Generally the first page retrieved when accessing a Web site. Usually a
"home" page acts as the starting point for a user to access information on the site. The
"home" page usually has some type of table of conte
nts for the rest of the site information
or other materials.


When creating Web pages, the "home" page has the filename
"index.html," which is the default name.


The "index" page automatically opens up as the
"home" page.



HTML

-

A type of text code in H
ypertext Markup Language which, when embedded in a
document, allows that document to be read and distributed across the Internet

HTTP
-

The hypertext transfer protocol (http) that enables html documents to be read on
the Internet.

IP Address

-

(Internet P
rotocol) The number or name of the computer from which you
send and receive information on the Internet.

Web server:

A

computer program that is responsible for accepting HTTP requests from
web clients, which are known as web browsers, and serving them HTTP

responses along
with optional data contents, which usually are web pages such as HTML documents and
linked objects (images, etc.).


Getting connected to the Internet

:

There are several ways of connecting to the Internet, from a simple dial
-
up link using

a
standard telephone line to faster and "always on" connections using a leased line, ISDN,
ADSL, ‘cable’, satellite, terrestrial fixed and mobile wireless. The faster the connection
the greater its capacity, enabling the fast transfer and download of data

across the
Internet.

The technological barriers to using the Internet are rapidly coming down, and emerging
technologies are predicted to revolutionise the market over the next few years. Permanent
connections are eventually expected to predominate in bo
th the residential and business
sectors together with access through TV sets, mobile phones, lap
-
top and handheld
computers and all manner of similar devices.


12



How is the speed of a connection measured?

The type of connection you use has a direct effect

on the speed with which you will be
able to use the Internet. The capacity of an Internet connection is referred to as its
bandwidth, and is measured in bits of data per second, a bit being an on or off, 1 or 0
signal. A thousand bits is a Kilobit (Kb), a

million bits is a Megabit (Mb), a thousand
million bits is a Gigabit (Gb) etc. However, data files are measured in Bytes, KiloBytes
(KB), etc, with a Byte calculated as eight bits.

So, a 1MB file is 8,000,000 bits and, in theory, will take 200 seconds (3

minutes 20
seconds) to transfer over a perfect 40kb/s (40,000 bits per second) connection.

Always bear in mind that your connection is constrained by the slowest component of the
network and the amount of data being transmitted across it at the time. Bot
tlenecks on the
other end of the link and even en route may also affect transmission times, and imperfect
connections can lead to errors and delays. Some transmission devices and software
compress files, reducing the amount of data and transmission time, b
ut additional data is
added to the file size by network and transmission protocols.

Using a dial
-
up connection

A standard telephone line and a modem is the entry
-
level connection to the Internet. The
modem translates the analogue telephone signal into a d
igital signal recognised by a
computer, and the connection is initiated by dialling an ISP's Internet access telephone
number. There is generally a local telephone call cost and/or an ISP subscription charge,
although charging models are many and various.
Data can flow both ways, but only when
a connection is live. So e
-
mail sent to you will only be received the next time you connect
to your ISP, and similarly remote Internet users will not be able to access your computer
or network unless you have initiate
d a connection.

Modems may be either an internal PC card or an external box. The standard download
speed, the speed at which your computer receives information, is up to 56kb/s, while the

13

upload speed, the speed at which your responses are sent back, is u
p to 33.6kb/s. Two (or
more) modems and telephone lines can be "teamed", brought into operation and dropped
automatically according to data transfer demand, to increase the available bandwidth.

With an ISDN line your computer will connect more quickly tha
n with a modem, in
around one second as opposed to 20
-
30 seconds, and data is sent and received at a
constant 64kb/s. ISDN connections are also generally more stable. The ISDN equivalent
of a modem is a terminal adapter, either an internal card or an exter
nal box, which can be
plugged directly into an ISDN telephone socket. Two or more channels can be "BonDed"
using a multiplexer to increase throughput, creating "bandwidth on demand" and data
rates of 128 kb/s upwards, depending on the number of channels av
ailable.

Using a permanent connection

A permanent connection is like a permanently open telephone line, with call charges
incorporated into your ISP subscription and/or line rental charge. With a permanent
connection e
-
mail can be delivered and received i
nstantly, and other applications such as
website hosting and videoconferencing become possible options.



leased line
-

runs between you and your ISP. Can be almost any bandwidth in
multiples of 64kb/s up to and beyond 2Mb/s, although higher bandwidths are
only
normally appropriate for ISPs and large organisations. Costs from £500 for
installation, plus around £3000 pa rental.



ADSL
-

a permanent, high
-
speed digital connection run on a standard copper
phone line, with the added advantage of allowing you to m
ake voice calls at the
same time as accessing the Internet. Technically ADSL links can provide a
download speed of up to 9Mb/s (upload speed at 640 Kb/s), but bandwidth
capability deteriorates with distance from the telephone exchange and the highest
pract
ical commercial rate is likely to be 2Mbps/256kbps. Availability is
improving and BT claims to be on target to reach 95% of the UK population by
the end of 2005. Costs from around £20 + VAT per month plus line rental for a
512/256 kbps service.


14



cable TV
-

connections to the Internet over cable TV networks are available in
many parts of the UK. A cable modem costs around £500, but can be leased from
the provider as part of the total monthly subscription charge of £20
-
£60. Cable
modem connections are technic
ally capable of download speeds of up to 10Mb/s,
with an upload speed of up to 2Mb/s or 10Mb/s depending upon the system, but
bandwidth is shared by all concurrent users of the network and individual
connections may be capped at 512kb/s or less to differen
tiate commercial
offerings.



fixed wireless and satellite access technologies are a bit more expensive than
ADSL and cable but are gaining ground in areas which are outside the technical
or commercially viable reach of such technologies. WiFi


(802.11 stan
dard)
‘hotspots’ are springing up in airports, railway stations, hotels, coffee shops etc.
where local wireless network connections are available if you have a wireless card
in your laptop and a subscription to the relevant service.


Accessing the Interne
t without a computer

Connecting to the Internet is also increasingly viable using familiar household gadgets,
such as a television or mobile phone. Alternative ways of accessing the Internet include:



via a mobile phone
-

hard to avoid, the latest mobile ph
ones offer Internet access
on the move using WAP (wireless application protocol) and GPRS, and ‘3’ now
offer third generation UMTS over a growing network



via digital TV
-

the set
-
top box which brings you a deluge of digital channels will
also enable you t
o browse the Web and send e
-
mail from the comfort of your own
armchair if a telephone line can be plugged in to your set
-
top box.



via a games console
-

Sega's Dreamcast and the Playstation 2 have built
-
in
modems, and are considerably cheaper than a comput
er



via your fridge??


wired, WAP or ‘Bluetooth’ local wireless technology in
conjunction with a PC and an always

on connection can make any device
Internet
-
enabled
-

such as the office security system, your central heating,

15

curtains, lights, video
-
door
-
p
hone
-
lock
-
system
-

and even your fridge so it can
automatically re
-
order when you run out of beer or low fat active yoghurt.


USES OF INTERNET

Nowadays internet has become so common that people who are unaware about internet
are referred as clumsy. This i
s due to the speedy development of technology and
globalization. Societies are becoming more and more unified. You can easily contact to
the person sitting in a different country. You can share your knowledge, thoughts by
making the use of an internet. Stu
dy results have also traced the popularity of internet
usage. Last year's study has wind up that email is the topmost task which is conducted
online, followed by general surfing, News reading, shopping etc.

Internet shopping has also become popular amongst

users especially in developed
nations; this is because 'shop on internet' is more efficient than physically going into the
stores. The internet endow with the surroundings where shopper's demands are fulfilled.
Shopping on the internet also saves time and

we can select a better product without
having to travel a long distance. Using the internet, shopper can scrutinize the product's
prices from various stores by sitting on one place. Also they can now shop online for the
goods which normally get sold in a
foreign nation. Rather than having to travel to the
country to take the delivery of the goods, they can place the order online and get it
efficiently delivered.

Internet also gives us the prospective to communicate effectively and efficiently. For
example,

sending an email costs lower than posting a letter in the mail, especially for
people who have to communicate internationally. Besides this, an email can be sent
within a minute after it is written. For sending a mail we don't need to complete the
officia
l procedure such as Post Office and a mail box etc. The recipient of the email can
view it at any time and from any place, as it is a virtual means of communication, as
opposed to having a mail box where the letters get delivered.


16

Internet use is not only
limited to shopping and communication with people, but it also
provides the environment for news distribution and endorse the people to be updated with
the latest news. We can access the data easily wherever it may be across the world.
Internet is also a v
ery good form of communication for people who want to express their
own view points and feelings. For youngsters, internet is not only a place of knowledge
but it also has an entertainment aspect such as online games, downloading movies, music
etc. But thi
s is not the only reason the internet appeals to the younger generation. They
also agreed that the internet provides ease to research and university students. This is
because a large number of articles on the same topic can be found on the internet by just

one search.

To put it briefly, the popularity of the internet have contributed in the most part of
development of the society. You
can say that people are nowadays becoming more reliant
on the internet for their day to day work. Or we can also say that they are making the use
of this facility for their routine life to save time and cost. Ultimately, it's a tool that is
effective if us
ed properly and effectively.