computing environments

7/23/2019 Computing Environments

1/24

.Computing Environments

5.1. Mainframe Computing Environment

Computing Environment is a collection of computers, software, and networks that support the

processing and exchange of electronic information. It can collaborate across various software

installed on different machines at different physical and geographical locations as well, such an

environment is called Distributed Computing Environment. Figure . ! shows how different

computers are connected with each other globally, also they can be connected with different

devices like cell phones.

Critical applications "refer glossary# and bulk data processing re$uire computer environments

which can guarantee high reliability and stability. %ost such large scale,high end commercial

system architectures "refer glossary# are referred as %ainframes.

Mainframe Computing Environment

It usually refers to one or more very big computer"s# capable of supporting a large number of

simultaneous users and doing bulk calculations and data processing. It is usually used for

extensive operations like Enterprise &esource 'lanning "refer glossary# or transaction processing.

(he %ainframe environment "&efer Figure . )# is expensive and ensures very high level of

security and reliability supporting massive throughput "refer glossary# . For example consider

banking applications like calculating balance of multiple customers who are doing their

transaction simultaneously from different locations. *lso generating account statements for all

customers at the end of every month. (hese are all bulk operations re$uiring speed and accuracy.

%ainframes have come a long way from the E+I*C "Electronic +umerical Integrator *nd

Calculator# developed in !-) to todays I/% 0 series of mainframes which are used in

organi0ations like +ational *eronautics and 1pace *dministration "+*1*#.

1oftware for mainframes are written in following languages2

Page 1ASPIRE 2014 ( Introduction to Computer systems )


2/24

C3mmon /usiness43riented 5anguage "C3/35#

6ob Control 5anguage "6C5#

5.1.1. Storing Data on a Mainframe

3n computers data is stored in the form of binary bits that is, 7s and !s . Characters like *..8 are

formed with 9 bits called as /ytes. :hen we press a key on the keyboard eight bits get emitted

from the cable. *ll the keys are represented with an uni$ue combination of binary numbers that

is 7s and !s. *s we use 9 bits to store a single character, );9 < )= different type of patterns can

be stored. 3n %ainframes, we use a uni$ue 94bit pattern to store each character. (his

representation of characters and data in mainframe is referred as Extended /inary Coded

Decimal Interchange Code "that is E/CDIC#. >ere, every character uses storage of one byte inmemory.

For example, in E/CDIC,

(he number ! is represented as !!!! 777!.

(he number ) is represented as !!!! 77!7.

5.1.2. Mainframe Datasets

3n a mainframe the information is stored in datasets "files 4refer glossary #. Each dataset should

have an uni$ue name of maximum -- characters long in this format2

????????.????????.???????? "For example, *@A7)B).C1(3%E&.D*(*#

Following points should be considered while creating mainframe datasets.



3/24

* dataset name consists of segments or $ualifiers.

Each $ualifier has maximum eight characters and are separated by a period".#.

(he $ualifier or segment should start with a capital letter "alphabet#.

(he operating system looks into the segments to keep a track of groups of datasets. (he

first segment of the dataset name is its >igh4level ualifier ">5#.

Datasets should have meaningful names. For example, Customers data should be stored

in a file named C1(3%E&.D*(*. >ere customer and data are the two segments or

$ualifiers of your dataset name.

(o access or log4in to %ainframes, we need a (13 "refer glossary# 1E&4ID, which is similar to

user4id that we use to login to a windows machine.

1uppose your (134id is *@A7)B). 1o give the >igh4level $ualifier *@A7)B) to all your

datasets. (his way you can identify the datasets belonging to you.

For example, name your Customer dataset as *@A7)B).C1(3%E&.D*(*.

%ainframes have 1ecurity software products like &*CF" &esource *ccess Control Facility#

which control access to datasets. For example, you may want to grant read4only access to the file

*@A7)B).C1(3%E&.D*(* to other users. (his will prevent other users from making any

changes to your dataset.

5.1.3. Mainframe Programing

>igh level language like C3/35 is used for %ainframe programming. (here are online

mainframe compilers available as well as software like >ercules can be installed on any

3perating 1ystem to simulate a mainframe environment.

I/%s %1 3perating system"%ultiple irtual 1torage "refer glossary# # up to release

B.9"released in the year !9!# is also available. I/% provides a pre4configured starter system in

which you can do some coding to describe the configuration to be installed. (his is called 1ystem@eneration "1ysgen# that is, the process of setting up or installing an operating system on the

mainframe.

:e can code C3/354'rograms and run them using a 6ob "6C5 G 6ob Control 5anguage# on a

%ainframe4Computer using its (13 ser4id for a given time. &efer Figure . B for the basic

Page ASPIRE 2014 ( Introduction to Computer systems )


4/24

skeleton of a C3/35 'rogram. * C3/35 program is written in structures called divisions.

Divisions in turn can have many sections. 1ections can have many paragraphs.

(he %ainframe terminal has 97 columns on a line for coding. (he area from columns 9 to !! is

called *rea *. (he area between columns !) to H) is called *rea /. &efer Figure . - for a

sample program to display a message >ello :orld.

* C3/35 program has following divisions 2

IDENTIFICATIN DI!ISING (his division records useful information like author

name or date when the program was created. It should at least have the program name or

ID.

EN!I"NMENT DI!ISIN4 (his division tells the computer about the other

resources that the program will interact with "that is, its environment# such as printers,

disk drives, other files etc. example, 13&CE4C3%'(E&. I/% 'C. (his information

tells the configuration of the computer on which the program will execute.

DATA DI!ISING (his division defines the names that the program will use to refer to

the data that it manipulates. For example, 1E&4+*%E 'IC *"!#. (he 'IC "or the

'icture clause # states that the data stored in this 1E&4+*%E will be of type alphabets

only and a maximum of ! characters "like (om or 6ohn# can be stored in 1E&4+*%E.

P"CED#"E DI!ISING It is the starting4point of the C3/354'rogram. (he

programing instructions must be written inside this '&3CED&E DII1I3+. In'&3CED&E DII1I3+ we can write instructions one4after4the other. (he %ainframe

executes these instructions one4by4one and step4by4step se$uentially. (he last4instruction

must be 1(3' &+ to stop running the C3/35 'rogram.



5/24

5.2. Net$or%s

* computer network oins two or more different categories of computing devices enabling them

to communicate to each other by sending and receiving instructions. * computer network can be

wired or wireless. *lso, smaller networks in turn may be connected to larger networks through

bridges, gateways or routers "refer glossary# . Communication in a network follows certain rules

that is, it is protocol "refer glossary# based.

Following are the maor categories of a Computer +etwork2

5*+ "5ocal *rea +etwork# 2 * 5*+ connects computer devices over a short distance. *

networked office, school or home usually contains a single 5*+ and occasionally it mayconnect a group of nearby buildings. 5*+ is mostly connected using a technology called

Ethernet "refer glossary#.

:*+ ":ide *rea +etwork# 2 * :*+ is a geographically4dispersed collection of multiple

5*+s. arious 5*+s are connected to a :*+ using a router. (he Internet is the largest

:*+ and it spans the Earth. :*+ networks exist under collective or distributed

ownership and management and do not belong to any single organi0ation.

:5*+ ":ire 5ess *rea +etwork# 2 * :ireless 5ocal *rea +etwork ":5*+# links two

or more devices using some wireless method that is without any physical cables. (hisenables the to move around within a local coverage area while being connected to the

network. :5*+s are used in places like in4home networks, airplanes, trains, restaurants,

hotels.

Page !ASPIRE 2014 ( Introduction to Computer systems )


6/24

Computer networks "refer glossary# can be classified according to the hardware and associated

software technology that is used to interconnect the individual devices in the network like

electrical cable, optical fiber, and radio waves "wireless 5*+#.

* well4known family of communication media is collectively known as Ethernet. Ethernet uses

various standards and media to enable communication between computer devices.

:ireless 5*+ technology connects computer devices without the use of wires or cables.

(hese devices use transmission mediums like radio waves or infrared signals as shown in Figure

. where a desktop computer, a laptop and a cell phone are all connected using wireless

technology. Figure . 2 Computer +etwork

5.2.1. &ire' Te()no*ogies

:ired networks are of following types 2

a. (wisted 'air

b. Coaxial Cable

c. 3ptic Fiber

a. T$iste' Pair

It is the most widely used medium for telecommunication. It is made of copper wires that are

twisted into pairs.

Page "ASPIRE 2014 ( Introduction to Computer systems )


7/24

3rdinary land line telephones are a good example where the wires consist of two

insulated copper wires that are twisted into pairs.

Computer network cabling "wired Ethernet# consists of - pairs of copper cabling that can

be utili0ed for both voice and data transmission. (his twisting of two wires together helps

to reduce crosstalk "refer glossary# and electromagnetic induction.

Its transmission speed varies from ) million to !7 billion bits per second. (he (wisted

pair cables are of two types2 nshielded (wisted 'air "('# and 1hielded (wisted4'air

"1('#.

+. Coa,ia* (a+*e

It is generally used for cable television, office buildings, and other work4sites for local area

networks.

(he cables consist of copper or aluminum wire surrounded by an insulating layer, which

in turn is surrounded by a conductive layer. (his insulation helps in minimi0ing

interference and distortion.

Its transmission speed is between )77 million bits per second to more than 77 million

bits per second

(. pti(a* fi+er

It is a glass fiber. It makes use of pulses of light to transmit data.

Its advantages over metal wires include less transmission loss, immunity from

electromagnetic radiation, and very fast transmission speed, up to trillions of bits per

second.

Page #ASPIRE 2014 ( Introduction to Computer systems )


8/24

Different colors of lights can be used to increase the number of messages being sent over

a fiber optic cable.

5.2.2. &ire*ess te()no*ogies

:ireless network refers to computer network that is not connected by cables of any kind.

:ireless networks can be of following types2

:ireless '*+ 4 :ireless personal area networks ":'*+s# interconnect devices within arelatively small area, generally within a persons reach. /luetooth radio or invisible

infrared light provide a :'*+ for connecting a headset to a laptop.

:ireless 5*+ 4 * wireless local area network ":5*+# links two or more devices over a

short distance using a wireless method providing a connection through an access point for

Internet access. (he use of spread4spectrum or 3FD% "refer glossary# technologies may

Page $ASPIRE 2014 ( Introduction to Computer systems )


9/24

allow users to move around within a local coverage area, still remaining connected to the

network.

:ireless mesh network 4 It is made up of radio nodes organi0ed in a mesh topology

"&efer section ).).B +etwork (opology#. Each node forwards messages on behalf of the

other nodes. %esh networks can automatically re4route around a node that has lost

power.

:ireless %*+ 4 :ireless metropolitan area networks are a type of wireless network that

connect many wireless 5*+s. :i%*? is an example of :ireless %*+.

:ireless :*+ 4 :ireless wide area networks are wireless networks that typically cover

large areas, like networking neighboring towns and cities.

Cellular network 4 * cellular network or mobile network is a radio network distributedover land areas known as cells. Each cell has at least one fixed4location transceiver" It is

usually installed on a communication tower and basically has the role of sending and

receiving signals#, known as a cell site or base station. (hese cells are oined together to

provide radio coverage over a wide geographic area and enable a large number of

portable transceivers "e.g., mobile phones, tablets# to communicate with each other.

Following (echnologies are used to support the :ireless network connections2

(errestrial microwave communication G It uses Earth4based transmitters and receivers

resembling satellite dishes "refer Figure .!!#. (errestrial microwaves are in the low4gigahert0 range limiting all communications to line4of4sight. (he relay stations are placed

approximately -9 km "B7 mi# apart.

Communications satellites 4 (hese communicate via microwave radio waves. (hese

waves are not deflected by the Earths atmosphere. (hese satellites stationed in space

typically in geosynchronous orbit B,-77 km ")),777 mi# above the e$uator "&efer Figure

.!7# can receive and relay data, voice and ( signals.

1pread spectrum "refer glossary# technologies use a high4fre$uency radio technology to

enable communication between multiple devices in a limited area.

Infrared communication can transmit signals for small distances typically less than !7

meters. It uses line4of4sight propagation which limits the physical positioning of

communicating devices.

Page %ASPIRE 2014 ( Introduction to Computer systems )


10/24

5.2.3. Net$or% topo*og-

* network topology is the layout describing how the nodes"all computer terminals# of a

computer network are interconnected. Common layouts are explained as follows2

us Net$or%



11/24

*ll nodes are connected to a common cable which is called a /us.

A'vantages

Implementation is easier.

/est (opology for small networks

Disa'vantages

Due to the cable length, the number of nodes that can be connected is also less.

It can perform well for a limited number of nodes only.

If the main cable or the /us fails, then all the nodes connected to it also fail to serve.

Star Net$or%

*ll nodes are connected to a central node or hub. (his layout found typically in a :ireless 5*+,

where each client connects to the central :ireless access point.

A'vantages

*s it is centrali0ed in nature, it is simple in terms of operation.

It also keeps each device isolated in the network. It means if one node stops working, it

does not affect the function of other nodes.

Disa'vantages

(he whole network operation is dependent on the central hub.

(he entire network fails if the central hub fails.

"ing Net$or%

A'vantage

(here is no re$uirement of a central server as the communication between two nodes

channeli0es through all the intermediate nodes.



12/24

Disa'vantages

Even if a single node of the network fails, it can cause the entire network to fail.

Entire network is affected whenever any change or movement is made for a network

node.

Mes) Net$or%

Each node connects with a random number of neighbors such that there is at least one traversal

from each node to any other. >ere each node has the responsibility of propagating the data.

A'vantage

(his arrangement of the network nodes makes it is possible to transmit data from one

node to many other nodes at the same time.

Disa'vantage

In an arrangement where each node is connected to every other node of the network,

many of the connections may serve no maor purpose as they behave as redundant

connections.

Fu**- Conne(te' Net$or%

Each node connects with all the other nodes in the network.

A'vantages

* fault in one terminal on the network will not effect other nodes, as the data has multiple

redundancy paths that can be used.

Data transfer rates can be kept at an acceptable level as whenever network usage is high

the data can be transmitted via different route hence reducing network clogging.

Disa'vantage

It re$uires a large amount of wiring.



13/24

5.2./. Net$or% Programming

Computer network programming involves writing computer programs that communicate with

each other across a computer network. :e need two separate programs for this. (he Client

program initiates the communication and (he server program which waits or listens for the

communication from client. /oth endpoints of the communication flow are called networksockets. +etwork programming is also known as socket programming.

+etwork 'rograming can be implemented using any language which needs to provide following

network layer functions. &efer Figure .!B.

socket"# creates a new socket, identified by an integer number, and allocates system

resources to it.

bind"# is used on the server side to associate a socket with a socket address structure, that

is a specified local port number and I' address.

listen"# is used on the server side and it causes a bound (C' socket to enter listening

state.

connect"# is used on the client side to assign a free local port number to a socket. For (C'

socket, it causes an attempt to establish a new (C' connection.



14/24

accept"# is used on the server side to accept a received incoming attempt to create a new

(C' connection from the remote client. It creates a new socket associated with the socket

address pair of this connection.

send"#4recv"#, write"#4read"# or sendto"#4recvfrom"# can be used to send and receive data

tofrom a remote socket.

o (he methods send"# and recv"# are used for sockets using (C' that is

(ransmission Control 'rotocol like >(('. (his mechanism has error checking

and guarantees no data loss. It is used for all such applications where you can not

allow data loss like browsing websites.

o (he methods sendto"# and recvfrom"# are used for sockets using D' "ser

Datagram 'rotocol like oice over Internet 'rotocol or 3I' used to make phone

calls using internet. (his has lower level of security and does not guarantee thatthe data will reach its destination.#

close"# causes the system to release resources that are allcated to a socket. (he connection

is terminated in case of (C' sockets.

unlink"# removes the file names created for the socket. 1o now the socket is removed and

new socket with same name can be created when re$uired.

1ome additional methods that can be used are as follows2

gethostbyname"# and gethostbyaddr"# are used to resolve hostserver names and

addresses.

select"# is used for one or more of a provided list of sockets to be ready to read or ready

to write.

poll"# is used to check the sockets state. (he whole set of sockets can be tested to see if

we can read or write to any socket or if an error occurred.

setsockopt"# is used to set the socket option for the given socket. (hese options can be

like 13JKEE'*5IE "keep the connection alive by periodic transfer of messages#,

13J/&3*DC*1( "*llows a single message to be sent "broadcasted# to all the

networked clients#, etc.

getsockopt"# gives the current value of a socket option for the specified socket.



15/24

5.3. Internet

(he Internet is a network connecting computers from across the world enabling data exchange

between them. Internet consists of independent hosts following the protocols. (he :orld :ide

:eb is a way of exchanging information over this medium of internet. (he system consists of at

least two computers connected in such a way that at any instance of time one acts as a client

"re$uesting data or service# and the other machine works as a host or server "providing the data

or service#. (he Internet can be accessed almost anywhere in many ways. Data cards, mobile

phones, hand4held game consoles and cellular routers provide wireless connection to the

Internet.

Page 1!ASPIRE 2014 ( Introduction to Computer systems )


16/24

5.3.1. Internet Proto(o*s

* protocol is a common means or rules for unrelated obects to communicate with each other. *

protocol is a description of2

(he messages that are understood by both the communicating obects.

(he arguments or data that these messages may be supplied with.

(he types of results returned by these messages.

(he information that is preserved despite modifications to the state of an obect.

*ny exceptional situations that needs to be handled during this communication.

(he protocol used for data flow or communication between the networks connected in an internet

is called Internet 'rotocol. (he Internet protocol suite is a model architecture that divides

methods into a layered system of protocols.

(he layers represent the scope or environment in which their services operate. "refer Figure

.!#. (he layers are as follows2

App*i(ation 0a-er 4 It is the space for the application4specific networking methods used

in software applications like a web browser program.

Transport *a-er4 It connects applications on different hosts via the network "like clientG

server model# with appropriate data exchange methods.

Internet *a-er 4 It enables computers to identify and locate each other via Internet

'rotocol "I'# addresses. It connects them to one another via intermediate "transit#

networks. "refer Figure .!=#.

Soft$are *a-erG It is the link layer and provides connectivity between hosts on the same

local network link, such as a local area network "5*+# or a dial4up connection.

(he model known as (C'I', is designed to be independent of the underlying hardware.

Internet 'rotocol "I'# is the most prominent component of the Internet model. It provides

addressing systems "I' addresses# for computers on the Internet.

Page 1"ASPIRE 2014 ( Introduction to Computer systems )


17/24

I' ersion - "I'v-# is the initial version of Internet 'rotocol. It was designed to address up to

approximately -.B billion "!7# Internet hosts and is still in dominant use.

* new protocol version I'v= was developed in the mid4!7s and is currently in growing

deployment around the world. It provides vastly larger addressing capabilities and more efficient

routing of Internet traffic.

5.3.2. Internet "outing

I' forwarding also known as Internet routing is a process used to determine the path for your

data contained in structures called datagrams or packets "refer glossary# . (he process uses

routing information to make decisions and is designed to send a packet over multiple networks.

Internet 1ervice 'roviders "I1's are the organi0ations that provide access to internet# connect

their customers to those of other I1's.

*t the top of the routing hierarchy are (ier4! networks held by large telecommunication

companies which exchange traffic directly across to all other (ier4! networks via agreements

such that they dont have to pay each other for the data transferred every now and then .

(ier4) networks buy Internet transit from (ier4! I1' to reach the global Internet. (hat is, to reach

a remote network, the smaller I1's have to connect to first (ier4! network which in turn may be

connected to that remote network. For this connectivity they have to pay some amount.

I1's generally use a single upstream provider for connectivity. (hey may use multihoming "refer

glossary# to provide protection from problems with individual links.

Page 1#ASPIRE 2014 ( Introduction to Computer systems )


18/24

Internet exchange points hold the physical connections between multiple I1's.

Computers and routers use routing tables "&efer Figure .!H# to direct I' packets among locally

networked machines. (hese tables can be constructed manually or automatically via D>C'

"Dynamic >ost Configuration 'rotocol# for an individual computer or a routing protocol for

routers themselves. In single4homed networks, a default route usually points up toward an I1'

providing transit. (he higher4level I1's use the /order @ateway 'rotocol "refer glossary# to

determine paths to any given range of I' addresses across the complex connections of the global

Internet.

Page 1$ASPIRE 2014 ( Introduction to Computer systems )


19/24

5./. &e+sites

* website is a set of related web pages containing information in form of text, images, audio,

video etc. * website is hosted on one or more web server"s# and can be accessed by internet.

:orld :ide :eb ":::# is the term used to refer collection of all public websites.

* web page is a single document written in plain text. It is formatted using instructions of

>ypertext %arkup 5anguage ">(%5#.

(he general features of a website are described as follows2

* protocol is a common means or rules for unrelated obects to communicate with each other. *

protocol is a description of2

(he home page of a website contains an introduction to that site and links to other related

pages or to other websites.

* website can be owned by an organi0ation or an individual also.

:ebsites may host static content that remains same for all the viewers or they may host

dynamic content that changes as per the visiting users preferences.

(o access a website, we need its address. For example, www.tcs.com

(he letters in the website address after the last dot ".# indicates the type of websites. For

example, .com means Commercial 3rgani0ation, .edu refers to educational sites, .gov is

for government websites, .obs means ob websites, etc.

* website is accessed using >ypertext (ransfer 'rotocol ">(('# . It may also use

encryption ">((' 1ecure, >(('1 "refer glossary# # to provide security and privacy.

(he users web browser understands the >(%5 instructions and displays the page content

accordingly.

Page 1%ASPIRE 2014 ( Introduction to Computer systems )


20/24

5./.1. Stati( $e+site

* static website usually displays the same information "static information# to all visitors. It is

similar to a printed brochure.

It provides consistent and standard information for a considerable long period.

(he website may however receive updates occasionally. (hese updates are done using a manual

process to edit the text, photos and other content. (his kind of editing re$uires a software and

basic skills to use it.

1tatic websites can be edited using the following categories of software2

(ext editors 4 >ere content and >(%5 markup are manipulated directly within the editor

program. For example, +otepad, +otepadLL.



21/24

:A1I:A@ "refer glossary# offline editors G (hese provide a @I interface. (he output

is in form of >(%5 markup generated automatically by the editor software. For example,

%icrosoft Front'age and *dobe Dreamweaver

:A1I:A@ online editors G (hese can be used to create online web pages including

widgets, blogs, and other documents containing images and other media. For example,

1napEditor.

(emplate4based editors 4 (hese allow $uick creation and uploading of web pages to a

web server. * detailed >(%5 knowledge is not re$uired. Aou ust need to pick a desired

template from available options and add pictures and text to it without directly writing or

updating >(%5 code. For example, &apid:eaver and i:eb.

5./.2. D-nami( &e+site

* dynamic website has the ability to change or customi0e itself fre$uently and automatically at

some specific time interval or based on some criteria.

Dynamic websites offer dynamism in two aspects 2 Code and Content. (he dynamic code

execution is not visible to the user. (he user can see the dynamic content only.

D-nami( (o'e4 (he code is executed on the fly based on some user event. 1cripting languages

like 6avascript, *ax are used for this. * website with dynamic code has followingcharacteristics2

It recalls all the bits of information from a database and consolidates them in a predefined

format.

It interacts with users in various ways like using cookies for finding previous history.

Direct interaction using form elements and mouse hovers also reflect the user event and

cause the dynamic code to execute.

It can display the current state of a interaction between users. It can capture information

personali0ed to the re$uirements of the user.

D-nami( (ontent 4 (he web page content keeps on varying based on some criteria, either

predefined rules or variable user input.



22/24

For example, a news website can use a predefined rule which tells it to display all news

articles for todays date and for your country or location only.

1uch a website automatically shows the most current news articles on any given date.

Consider a retail website which allows a user to input a search re$uest for the keyword

like @uitar. In response, the content of the web page will spontaneously change and will

then display a list of @uitar and music products like CDs "Compact Disks# and DDs

"Digital ersatile Disk#.

Summar-

Computing Environment is a collection of computers, and various software in a network.

*ll these computers collaborate with each other for storing,processing and exchanging

electronic information.

%ainframe computing environment is capable of doing bulk calculations with very high

level of accuracy,security and speed.

%ainframe programs are written using C3/35 and 6C5. :e need a (13 "refer glossary#

user id to access the time slot on a mainframe server.

* computer network oins two or more computing devices so that they can communicate

with each other. +etworks can be of two types that is, wired or wireless.

(wisted pair, Coaxial cables and 3ptic fiber technologies are used to connect a wired

network.

(errestrial %icrowave, 1atellites, 1pread 1pectrum and Infrared technologies are used to

connect various computing devices without wires.

Computer networks can have their nodes connected in forms like /us, 1tar &ing, %esh or

Fully Connected topology.

+etwork or 1ocket programing can be done using various programing language and all of

them provide the basic methods for reading and writing to a network and listening for

re$uests from the client.

Internet connects computers across the world. It is based on protocols. Each computer in

the internet is identified by an I' address.



23/24

(he communication between two computers may be routed through various networks.

* :ebsite may be accessed using http protocol from any where on the internet. It can be

of two types 2 1tatic and dynamic.

1tatic websites are like the profile of a company or product and does not change often

and displays the same details to all visitors.

Dynamic websites change their content as per time and user preferences like news, e4

commerce websites.

Dynamic code 4 (he code is executed on the fly based on some user event. 1cripting

languages like 6avascript, *ax are used for this. * website with dynamic code has

following characteristics2

o It recalls all the bits of information from a database and consolidates them in a

predefined format.

o It interacts with users in various ways like using cookies for finding previous

history.

o Direct interaction using form elements and mouse hovers also reflect the user

event and cause the dynamic code to execute.

o It can display the current state of a interaction between users. It can captureinformation personali0ed to the re$uirements of the user.

Dynamic content 4 (he web page content keeps on varying based on some criteria, either

predefined rules or variable user input.

o For example, a news website can use a predefined rule which tells it to display all

news articles for todays date and for your country or location only.

o 1uch a website automatically shows the most current news articles on any given

date.

o Consider a retail website which allows a user to input a search re$uest for the

keyword like @uitar. In response, the content of the web page will spontaneously

change and will then display a list of @uitar and music products like CDs

"Compact Disks# and DDs "Digital ersatile Disk#.



24/24

Page 24

computing environments

Documents