Notes e commerce

IT63 WEB TECHNOLOGY
L.A.ANTO GRACIOUS, Lect/IT Marthandam College of Engineering and Technology
Kuttakuzhi
UNIT 1
1. Explain in detail about the basic internet protocols.
The OSI-ISO model consists of 7 layers and at each layer one or more protocols are used to
handle the transmission of data. The layers and the associated protocols are given in the table:
Layers Name Protocols used
7 Application SSH, FTP, Telnet
6 Presentation HTTP, SNMP, SMTP, POP3
5 Session RPC, named pipes, NETBIOS
4 Transport TCP, UDP
3 Network IP
2 Data Link Ethernet
1 Physical Cat-5
TCP - Transmission Control Protocol
The Transmission Control Protocol (TCP) is one of the core protocols of the Internet
Protocol Suite. TCP is one of the two original components of the suite, complementing the
Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP. TCP
provides reliable, ordered delivery of a stream of bytes from a program on one computer to
another program on another computer. TCP is the protocol that major Internet applications
such as the World Wide Web, email, remote administration and file transfer rely on. Other
applications, which do not require reliable data stream service, may use the User Datagram
Protocol (UDP), which provides a datagram service that emphasizes reduced latency over
reliability.
The TCP is widely used for:
• Safety delivery of data
• Error detection
• Assurance of the correct sequencing of data being received.
The TCP protocol is a connection oriented protocol because before sending the data
this protocol requires that the two computers have established connections. The TCP allows
the transmission by breaking the data into stream of IP packets. These IP packets are
numbered so that they can be reassembled properly. Along with the data an acknowledgment
is also sent/received to know whether the reliable connection is occurred or not. TCP protocol
provides the full duplex communication process.
The below shown figure shows the operation of a TCP protocol.

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The TCP protocol ask the destination whether it can make a connection with the
destination and if the destination gives the acknowledgement then the connection will be
made by sending an acknowledgement. Then the source machine sends the data in the form
of packets and if the packet is received then the acknowledgement message is sent back to the
source. While sending the data the source maintains a timer and if the destination did not
send the acknowledgement within the time limit it again resends the data to the destination
until the acknowledgement is send to the source from the destination.
TCP also adds concept of a port, which allows TCP to communicate with many different
applications on a machine. TCP header contains port number representing an application
program on the destination computer. Some port numbers have standard meanings. Example:
port 25 is normally used for email transmitted using the Simple Mail Transfer Protocol
(SMTP). Other port numbers are available first-come-first served to any application.
Simplified view of communication using TCP/IP
Here the port operation is carried out by the TCP protocol.

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• Mail server on Host B sends a message to TCP software located on Host B.
• The TCP software then tells IP software on Host B.
• Now from Host A the data is send to TCP software on Host A. TCP software attaches
the TCP header to the data.
• The data is then sent to the IP software. IP software attaches the IP header to the data.
• The encapsulated data with IP and TCP header will then be traversed over the
network. It will be sent to the IP software running on the Host A.
• Host A will remove the IP header and sent the packet to the TCP software.
• The TCP software running on the Host A will remove the TCP header and send only
the data to the mail server. Thus mail server running on the Host A accepts the data
sent by mail client on Host B.
IP – Internet protocol
IP is a network layer protocol which consists of addressing information. Using this
information the communication between uniquely addressed computers is possible. The
internet protocol decomposes the information into packets of standardized size and then
reassembles the data at the destination point. The internet protocol route the packet through
the successive network and then to the network. The destination to which the data has to be
send will be identified by its IP address.
• If the source machine wants to send the data to the destination machine, it is necessary
to have the IP software to be run on both the machines. The main function of the IP
software is to transfer the data from source to destination.
• When the source wants to send the data to the destination machine then the source
calls the IP software running on it. It encapsulates the data to be transferred to
destination along with the IP address of source and destination. The IP software
running in source creates a packet. This packet consists of data+IP address of
source+IP address of destination+header.
• If the destination is on the same network then the packet is transferred over the
network. But if it is on another network then these two networks should get connected
together by a gateway. In this case source sends message to the gateway. The gateway
selects the computer on one of the network to which it is attached and send the
packets to the destination machine.
• The packet then travels through the network and then reaches the destination. Such
traversing is called routing.

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Routing
The sequence of computer that packet travels through from source to destination is
called as its route.
UDP – User Datagram Protocol
UDP is an alternative protocol to TCP that builds on IP. The main feature is the port
concept. It does not provide the two-way connection or does not provide guaranteed delivery.
Since it is called as unreliable protocol. UDP's stateless nature is also useful for servers
answering small queries from huge numbers of clients. Unlike TCP, UDP supports packet
broadcast (sending to all on local network) and multicasting (send to all subscribers).
Common network applications that use UDP include: the Domain Name System (DNS),
streaming media applications such as IPTV, Voice over IP (VoIP), Trivial File Transfer
Protocol (TFTP), IP tunneling protocols and many online games.
DNS – Domain Naming Service
The Domain Name System (DNS) is a hierarchical distributed naming system for
computers, services, or any resource connected to the Internet or a private network. It
associates various information with domain names assigned to each of the participating
entities. Most importantly, it translates domain names meaningful to humans into the
numerical identifiers associated with networking equipment for the purpose of locating and
addressing these devices worldwide.
An often-used analogy to explain the Domain Name System is that it serves as the
phone book for the Internet by translating human-friendly computer hostnames into IP
addresses. For example, the domain name www.example.com translates to the addresses
192.0.32.10 (IPv4).
The Domain Name System makes it possible to assign domain names to groups of
Internet resources and users in a meaningful way, independent of each entity's physical
location. Because of this, World Wide Web (WWW) hyperlinks and Internet contact
information can remain consistent and constant even if the current Internet routing
arrangements change or the participant uses a mobile device. Internet domain names are
easier to remember than IP addresses such as 208.77.188.166 (IPv4). Users take advantage of
this when they recite meaningful Uniform Resource Locators (URLs) and e-mail addresses
without having to know how the computer actually locates them.
The Domain Name System distributes the responsibility of assigning domain names
and mapping those names to IP addresses by designating authoritative name servers for each
domain. Authoritative name servers are assigned to be responsible for their particular
domains, and in turn can assign other authoritative name.
There are two tasks that can be carried out by DNS servers:
• Accepting and then requesting the programs to convert domain names into IP
addresses.
• Accepting and then requesting the other DNS servers to convert domain names to IP
addresses.

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Host names consist of a sequence of Labels separated by dots, e.g., www.example.org. Final
label is top-level domain with 2 standard types:
Generic : .com, .edu, .org, etc.
Country-code : .us, .ca, etc.
Domains are divided into second-level domains, which can be further divided into
subdomains, etc.
E.g., in www.example.com, example is a second-level domain.
A host name plus domain name information is called the fully qualified domain name
(FQDN) of the computer. Above, www is the host name, www.example.com is the FQDN.
nslookup program provides command-line access to DNS (on most systems). Looking up a
host name given an IP address is known as a reverse lookup. Note that single host may have
multiple IP addresses (and a single IP address can be associated with multiple domain
names). Address (or name) returned is the canonical IP address (or name) specified in the
DNS system. Other addresses (or names) are considered aliases.
FTP – File Transfer Protocol
File Transfer Protocol (FTP) is a standard network protocol used to transfer files from
one host to another host over a TCP-based network, such as the Internet. FTP is built on
client-server architecture and uses separate control and data connections between the client
and server. FTP users may authenticate themselves using a clear-text sign-in protocol but can
connect anonymously if the server is configured to allow it. In the second age, the first FTP
client applications were interactive command-line tools, implementing standard commands
and syntax. Graphical user interface clients have since been developed for many of the
popular desktop operating systems in use today.
There are various issues that must be solved during file transfer. They are:
• Client must have an authority to download a particular file.
• The hardware and software on both formats on client and server might be different.
• The data interpretation and data formats at client and server might be different.
FTP uses two connections between client and server. One connection is used for
actual file transfer and the other is used for control information. This separation of data and
commands makes the FTP more efficient.
HTTP – Hyper Text Transfer Protocol
The HTTP is a request/response protocol. It is a communication protocol used to
transfer the information on local area network and World Wide Web. It’s the network
protocol used to deliver all files and other data on the World Wide Web, whether they are
HTML files, image files or anything else.
A browser is a HTTP client because it sends request to an HTTP server which then
sends response back to the client. The standard port for HTTP servers to listen on is 80. The
get and post are two popular methods used by HTTP protocol. It is also called as a stateless
protocol because this protocol is not able to maintain the previous information.

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SNMP – Simple Network Management Protocol
SNMP is a protocol which enables network administrators to manage network devices
and to diagnose network problems. The network management system is based on two main
elements: a supervisor and agents. SNMP makes use of UDP connections for transferring the
SNMP messages. The supervisor is the terminal at which the network administrator request
for network management. The agents are found at the level of each interface connecting the
managed devices to the network. With the help of these agents information’s on the different
objects can be collected.
SMTP – Simple Mail Transfer Protocol
It is extensively used for transfer of emails to remote servers. It is an asynchronous
protocol because it allows delayed delivery of message. This protocol makes use of port 25.
With the help of mail transfer agent and user agent the SMTP sends and receives the email.
The mail transfer agent is the interface between email system and local email server. The user
agent is user interface client. It allows the user to read email messages by receiving it from
the server.
POP3 – Post Office Protocol Version 3
POP3 is used by local email clients. POP3 makes use of port 110. The POP3 protocol
works only at the receivers end and had no work at the senders end. The POP has two parts:
receivers POP and server POP. The client opens TCP connection with receiver’s POP server.
This client must be authenticated first by the user name and password. Then the client can
receive the emails from the mailbox.
2. Explain in details about some fundamental html elements.
• HTML is a language for describing web pages.
• HTML stands for Hyper Text Markup Language
• HTML is not a programming language, it is a markup language
• A markup language is a set of markup tags
• HTML uses markup tags to describe web pages
HTML Tags
HTML markup tags are usually called HTML tags
• HTML tags are keywords surrounded by angle brackets like <html>
• HTML tags normally come in pairs like <b> and </b>
• The first tag in a pair is the start tag, the second tag is the end tag
• Start and end tags are also called opening tags and closing tags
HTML Documents = Web Pages
• HTML documents describe web pages
• HTML documents contain HTML tags and plain text

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• HTML documents are also called web pages
The purpose of a web browser (like Internet Explorer or Firefox) is to read HTML documents
and display them as web pages. The browser does not display the HTML tags, but uses the
tags to interpret the content of the page:
<html>
<body>
<h1>My First Heading</h1>
<p>My first paragraph.</p>
</body>
</html>
Example Explained
• The text between <html> and </html> describes the web page
• The text between <body> and </body> is the visible page content
• The text between <h1> and </h1> is displayed as a heading
• The text between <p> and </p> is displayed as a paragraph
Editing HTML
HTML can be written and edited using many different editors like Dreamweaver and
Visual Studio.
.HTM or .HTML File Extension?
When you save an HTML file, you can use either the .htm or the .html file extension.
There is no difference; it is entirely up to you.
HTML Basic - 4 Examples
HTML Headings
HTML headings are defined with the <h1> to <h6> tags.
Example
<h1>This is a heading</h1>
HTML Paragraphs
HTML paragraphs are defined with the <p> tag.
Example
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

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HTML Links
HTML links are defined with the <a> tag.
Example
<a href="http://www.w3schools.com">This is a link</a>
Note: The link address is specified in the href attribute.
HTML Images
HTML images are defined with the <img> tag.
Example
<img src="w3schools.jpg" width="104" height="142" />
Note: The name and the size of the image are provided as attributes.
HTML Elements
HTML documents are defined by HTML elements.
An HTML element is everything from the start tag to the end tag:
Start tag * Element content End tag *
<p> This is a paragraph </p>
<a href="default.htm" > This is a link </a>
<br />
* The start tag is often called the opening tag. The end tag is often called the closing tag.
HTML Element Syntax
• An HTML element starts with a start tag / opening tag
• An HTML element ends with an end tag / closing tag
• The element content is everything between the start and the end tag
• Some HTML elements have empty content
• Empty elements are closed in the start tag
• Most HTML elements can have attributes
Tip: You will learn about attributes in the next chapter of this tutorial.
Nested HTML Elements
Most HTML elements can be nested (can contain other HTML elements). HTML documents
consist of nested HTML elements.
HTML Document Example
<html>
<body>

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<p>This is my first paragraph.</p>
</body>
</html>
The example above contains 3 HTML elements.
HTML Example Explained
The <p> element:
The <p> element defines a paragraph in the HTML document.
The element has a start tag <p> and an end tag </p>.
The element content is: This is my first paragraph.
The <body> element:
<body>
</body>
The <body> element defines the body of the HTML document.
The element has a start tag <body> and an end tag </body>.
The element content is another HTML element (a p element).
The <html> element:
<html>
<body>
</body>
</html>
The <html> element defines the whole HTML document.
The element has a start tag <html> and an end tag </html>.
The element content is another HTML element (the body element).
Don't Forget the End Tag
Some HTML elements might display correctly even if you forget the end tag:
<p>This is a paragraph
The example above works in most browsers, because the closing tag is considered optional.
Never rely on this. Many HTML elements will produce unexpected results and/or
errors if you forget the end tag.
Empty HTML Elements
HTML elements with no content are called empty elements.

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<br> is an empty element without a closing tag (the <br> tag defines a line break).
Tip: In XHTML, all elements must be closed. Adding a slash inside the start tag, like <br />,
is the proper way of closing empty elements in XHTML (and XML).
HTML Tip: Use Lowercase Tags
HTML tags are not case sensitive: <P> means the same as <p>. Many web sites use
uppercase HTML tags.
HTML Headings
Headings are important in HTML documents. Headings are defined with the <h1> to <h6>
tags.
<h1> defines the most important heading. <h6> defines the least important heading.
Example
Browsers automatically add some empty space (a margin) before and after each heading.
Coding:
<html>
<body>
<h1>This is heading 1</h1>
</body>
</html>
Output:

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Headings Are Important
Use HTML headings for headings only. Don't use headings to make text BIG or bold.
Search engines use your headings to index the structure and content of your web pages. Since
users may skim your pages by its headings, it is important to use headings to show the
document structure.
H1 headings should be used as main headings, followed by H2 headings, then the less
important H3 headings, and so on.
HTML Lines
The <hr /> tag creates a horizontal line in an HTML page. The hr element can be used to
separate content:
Example
<p>This is a paragraph</p>
<hr />
<hr />
Coding:
<html>
<body>
<p>The hr tag defines a horizontal rule:</p>
<hr />
<hr />
<hr />

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</body>
</html>
Output:
HTML Comments
Comments can be inserted into the HTML code to make it more readable and
understandable. Comments are ignored by the browser and are not displayed. Comments are
written like this:
Example

Coding:
<html>
<body>

<p>This is a regular paragraph</p>
</body>
</html>
HTML Paragraphs
HTML documents are divided into paragraphs. Paragraphs are defined with the <p> tag.
Example
<p>This is another paragraph</p>

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Note: Browsers automatically add an empty line before and after a paragraph.
Don't Forget the End Tag
Most browsers will display HTML correctly even if you forget the end tag:
Example
<p>This is another paragraph
Coding:
<html>
<body>
<p>This is<br />a para<br />graph with line breaks</p>
</body>
</html>
Output:
HTML Line Breaks
Use the <br /> tag if you want a line break (a new line) without starting a new paragraph:
Example
The <br /> element is an empty HTML element. It has no end tag.
<br> or <br />
Coding:
<html>
<body>
</body>

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</html>
Output:
In XHTML, XML, elements with no end tag (closing tag) are not allowed. Even if
<br> works in all browsers, writing <br /> instead works better in XHTML and XML
applications.
HTML Output - Useful Tips
You cannot be sure how HTML will be displayed. Large or small screens and resized
windows will create different results. With HTML, you cannot change the output by adding
extra spaces or extra lines in your HTML code. The browser will remove extra spaces and
extra lines when the page is displayed. Any numbers of lines count as one line, and any
number of spaces count as one space.
HTML Text Formatting
Coding:
<html>
<body>
<p><b>This text is bold</b></p>
<p><strong>This text is strong</strong></p>
<p><big>This text is big</big></p>
<p><i>This text is italic</i></p>
<p><em>This text is emphasized</em></p>
<p><code>This is computer output</code></p>
<p>This is<sub> subscript</sub> and <sup>superscript</sup></p>
</body>
</html>
Output:

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HTML uses tags like <b> and <i> for formatting output, like bold or italic text. These HTML
tags are called formatting tags (look at the bottom of this page for a complete reference).
Often <strong> renders as <b>, and <em> renders as <i>.
However, there is a difference in the meaning of these tags:
<b> or <i> defines bold or italic text only.
<strong> or <em> means that you want the text to be rendered in a way that the user
understands as "important". Today, all major browsers render strong as bold and em as
italics. However, if a browser one day wants to make a text highlighted with the strong
feature, it might be cursive for example and not bold!
HTML Fonts
The HTML <font> Tag Should NOT be Used
The <font> tag is deprecated in HTML 4, and removed from HTML5. The World Wide Web
Consortium (W3C) has removed the <font> tag from its recommendations. In HTML 4, style
sheets (CSS) should be used to define the layout and display properties for many HTML
elements.
The example below shows how the HTML could look by using the <font> tag:
Example
<p>
<font size="5" face="arial" color="red">
This paragraph is in Arial, size 5, and in red text color.
</font>
</p>
<p>

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<font size="3" face="verdana" color="blue">
This paragraph is in Verdana, size 3, and in blue text color.
</font>
</p>
Coding;
<html>
<body>
<p>
<font size="5" face="arial" color="red">
This paragraph is in Arial, size 5, and in red text color.
</font>
</p>
<p>
<font size="3" face="verdana" color="blue">
This paragraph is in Verdana, size 3, and in blue text color.
</font>
</p>
<p>The font element is deprecated in HTML 4. Use CSS instead!</p>
</body>
</html>
Output:
HTML Style Example - Font, Color and Size
The font-family, color, and font-size properties defines the font, color, and size of the
text in an element:
Example
<html>
<body>

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<h1 style="font-family:verdana;">A heading</h1>
<p style="font-family:arial;color:red;font-size:20px;">A paragraph.</p>
</body>
</html>
The font-family, color, and font-size properties make the old <font> tag obsolete.
Coding:
<html>
<body>
<h1 style="font-family:verdana;">A heading</h1>
<p style="font-family:arial;color:red;font-size:20px;">A paragraph.</p>
</body>
</html>
Output:
HTML Style Example - Text Alignment
The text-align property specifies the horizontal alignment of text in an element:
Example
<html>
<body>
<h1 style="text-align:center;">Center-aligned heading</h1>
</body>
</html>
The text-align property makes the old <center> tag obsolete.
Coding:
<html>
<body>
<h1 style="text-align:center;">Center-aligned heading</h1>

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</body>
</html>
Output:
3. Basic XHTML syntax and semantics
XHTML follows the following syntax
Documents in XHTML must always be well-formed
All XHTML Document can have only one root element that is <html>all other
elements should be nested within the root element. There will be only one parent called a root
element which can have its children (sub elements) nested within it. Sub elements must be in
pairs and correctly nested within their parent element. The basic document structure is:
(doctype)
<html xmlns="http://www.vyom.co.in/xhtml">
<head>
<title>...</title>
... </head>
<body>... </body>
</html>
Notice the (doctype) and the "xmlns" attribute on the opening html tag. You should also
include a character set Meta tag in the <head> element.
XHTML elements must be properly nested
Wrong:
<p>This is our site <em>paragraph.</p></em>
Right:
<p>This is our site <em>paragraph.</em></p>
Since XML is case-sensitive. Tag names must be in lowercase.

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Wrong:
<PRE>Some preformatted text.</PRE>
Right:
<pre>Some preformatted text.</pre>
All Attributes that are used here must be in lower case
Wrong:
<a HREF="http://www.vyom.co.in">
Right:
<a href="http://www.vyom.co.in">
All elements must be closed
This includes elements that traditionally do not contain any content, such as images, form
inputs, Meta tags, etc.
Wrong:
<p>Welcome to vyom.
<p>This is our website
Right:
<p>Welcome to vyom..</p>
<p>This is our website.</p>
Elements which dont have closing tags must be closed with slash inside the tag.
<br> becomes <br />
<hr> becomes <hr />
<input type="text">becomes <input type="text" />
All attributes values must be quoted
Wrong:
<a href=http://www.vyom.co.in>example link</a>
Right:
<a href="http://www.vyom.co.in">example link</a>
Attribute minimization is forbidden
Wrong:
<input type="checkbox" checked />
Right:
<input type="checkbox" checked="checked" />

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All image tags should have "alt" attributes.
Wrong:
<img src="kitten.jpg" />
Right:
<img src="kitten.jpg" alt="an evil kitten" />
The "id" attributes and the "name" attribute-
Element ids which should be unique eventually will replace element names. For now,
to ensure backsword-compatibility it is recommended to use both, for example, many of the
form fields are accessed by their names. In cascading style sheets and various scripting
languages Ids are used.
<img src="kitty.jpg" name="kittypic" alt="an evil kitten" />
<img src="kitty.jpg" name="kittypic" alt="an evil kitten" id="kittypic" />
The XHTML DTD defines mandatory elements
4. Briefly explain about the internet.
The internet is a global connection of people computers which are linked together by
cables and Telephone lines making communication possible among them in a common
language. Global connection of interconnected networks.
How does internet works?
The internet is used to move data between two specific computers. For moving the
data between two computers we require
- The address of the destination.
- A safe mean of moving data in the form of electronic signals
There exist a set of rules which governs the sending and receiving of data on the internet.
Rules are implemented in two parts in the network software.
- Transmission Control Protocol (TCP).
- Internet Protocol (IP).
It is called TCP/IP
Large block of text/ data, the TCP divides into little Data Packets and add some
special information like - packet position and Error correction code.
To make sure those packets at the destination can reassemble correctly and without
any damage to data. The role of IP here is to put destination addressing information on such
packets. It is not necessary that all the packets will follow the same path from source to
destination.
Special machines

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Routers are used to load balance various paths that exist on networks gateways
allows different electronic networks to talk to Internet which TCP/IP Addresses are essential
in the internet. The TCP/IP is a mechanism for providing addresses for computers on the
internet address has two forms:
Person understandable who expressed as words (Domain name) - www.kongu.edu
Machine understandable which repressed as numbers - 172.16.2.5.
Ex: murali@yahoo.com
username@host.subdomain.domain
Username - is the name of the Internet account.
Host - individual machines at a particular location.
Hosts and local networks are grouped together into domains, which are grouped into
one or more larger domains.
Ex: apartment-> complex -> town -> country.
Sub-domains may corresponds to organizations such as NASA or COMPUSERVE
such as India comes a large domain ‘in’
SUB-DOMAINS LARGE DOMAINS
com - commercial au - Australia
net - network usa - USA
mil - military in - india
org - organization sg - singapore
edu - education cn - canada
gov - government jp -Japan
int - international
Internet Addressing
Internet Address consists TWO parts
1. Network Address (Net ID)
2. Host Address (Host ID)
The IP address is grouped into 8-bits separated by dots.
There four types of internet address each 32 bit long:
No. of bits in net ID No. of bits in Host ID Format Range
CLASS A 8 24 N.H.H.H 1 to 126
CLASS B 16 16 N.N.H.H 127 to 191
CLASS C 24 8 N.N.N.H 192 to 223
CLASS D Multicasting all bits - 224 to 239
CLASS E For Future - 240 to 254
Here N stands for network address and H stands for Host address.
In which only CLASS A, B & C are mostly used. These may be used for:

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• Unicast - Single computer
• Multicast - Set of computers all reside in different location
• Any-cast - Set of computers all reside in single location.
What can I do on Internet?
Several activities can be performed if you have access to the Internet:
• To Publish research information
• To create campus wide information systems
• Use it for Teaching
• Use it with ISDN for multimedia conferencing
• Refer to the pictures of an art gallery
• Have an electronic copy of classics such as Alice in wonderland
• Have an electronic copy of journals and magazine from the Internet
• To meet people around the world
• To refer the job listings and requirements
• To get free public domain programs, Movies, songs etc.
• To send mail at any time
Tools and Services on Internet
• E-mail - mailbox
• Mailing List
• Usenet or Newsgroups
• File Transfer Protocol (FTP)
• Telnet (Remote login)
Browsing the internet
There are many browsers for the Internet. They are
• Internet Explorer ( IE )
• Netscape Navigator
• Mosaic etc.
Internet Standards
There are many standard organizations in the world. The two organizations are:
Internet Engineering Task Force(IETF) and
World Wide Web Consortium( W3c)
IETF is a relatively informal and it standards include TCP/IP, MIME, SMTP. The
W3C, by contrast, is a vendor organization, controlled by its dues-paying member
corporations and it standards include HTTP, HTML and XML
Internet Principles
• TCP/IP
• UDP

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• IP Addresses
• Domain Names
• Domain Name System
• Ports
• Sockets
• URL's
5. Briefly explain about XML
XML was designed to transport and store data but HTML was designed to display
data.
What is XML?
• XML stands for eXtensible Markup Language
• XML is a markup language much like HTML
• XML was designed to carry data, not to display data
• XML tags are not predefined. You must define your own tags
• XML is designed to be self-descriptive
• XML is a W3C Recommendation
The Difference between XML and HTML
XML is not a replacement for HTML. XML and HTML were designed with different
goals:
• XML was designed to transport and store data, with focus on what data is
• HTML was designed to display data, with focus on how data looks
• HTML is about displaying information, while XML is about carrying information.
XML Does Not DO Anything
Maybe it is a little hard to understand, but XML does not DO anything. XML was
created to structure, store, and transport information. The following example is a note to
Tove, from Jani, stored as XML:
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
The note above is quite self descriptive. It has sender and receiver information, it also
has a heading and a message body. But still, this XML document does not DO anything. It is
just information wrapped in tags. Someone must write a piece of software to send, receive or
display it.

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With XML You Invent Your Own Tags
The tags in the example above (like <to> and <from>) are not defined in any XML
standard. These tags are "invented" by the author of the XML document. That is because the
XML language has no predefined tags. The tags used in HTML are predefined. HTML
documents can only use tags defined in the HTML standard (like <p>, <h1>, etc.). XML
allows the author to define his/her own tags and his/her own document structure.
XML is Not a Replacement for HTML
XML is a complement to HTML.
It is important to understand that XML is not a replacement for HTML. In most web
applications, XML is used to transport data, while HTML is used to format and display the
data. XML is a software- and hardware-independent tool for carrying information.
XML is a W3C Recommendation
XML became a W3C Recommendation on February 10, 1998.
XML is Everywhere
XML is now as important for the Web as HTML was to the foundation of the Web.
XML is the most common tool for data transmissions between all sorts of applications.
Relationship between SGML, XML, HTML and XHTML.
6. Relative URLs.
URLs are used to locate anything, anywhere. Since their scope is so large, they often
get very long. It is often the case that we can abbreviate URLs in the form of relative URLs.
All the URLs we've looked at until now were absolute URLs. They identified a resource
independent of their context. The URL http://WebReference.com/html/ identifies HTML with

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Style whether it's typed into your browser, scribbled on a napkin in a bar for a friend or just
remembered in your head. Relative URLs are a way to identify a resource relative to their
context.
To give a rough analogy, if you're in your house with some friends and someone asks
where your next-door neighbor Mark lives, you'll probably say "Oh, he's next door." You
probably wouldn't say "On a planet called Earth, in the United Stated of America, in
Acmetown, on 32 Foobar St." if this conversation is taking place in the living room of 31
Foobar St. For one thing, it's a waste of breath.
Relative URLs are something like that; they're the equivalent of saying "down the
road, turn left, walk on for a few blocks, you can't miss it." They only make sense if they are
given within a certain context. And this context is called a Base URL.
As we mentioned earlier, relative URLs can only be used with generic URLs like the
ones described by the http scheme. The reason for this is that all generic URLs, like those
defined by the http scheme, have a pathname. The Base URL of a resource is everything up
to and including the last slash in its pathname. Here are some examples:
Absolute URL Base URL
http://WebReference.com/ http://WebReference.com/
http://WebReference.com/html/ http://WebReference.com/html/
http://WebReference.com/html/about.html http://WebReference.com/html/
http://WebReference.com/foo/bar.html?baz http://WebReference.com/foo/
Table 1: Examples of Base URLs
Now, say that in the document http://WebReference.com/html/about.html, I want to
refer to the document http://WebReference.com/html/links.html. What I would do is use the
relative URL links.html. This will be added to the base URL to form the URL that I want to
match. In most cases, figuring the absolute URL from a relative URL is just a matter of
concatenating the base URL and the relative URL, as in the example above. There are,
however, a few special cases:
A directory called .. (two periods) in a relative URL indicates the parent directory,
essentially stripping off everything up to the previous slash in the the Base URI. Note that
this only has meaning inside the pathname, so you cannot use this notation to go up higher
than the root directory.
A directory called . (one period) refers to the current directory. A relative URL that begins
with / (a slash) always replace the entire pathname of the base URL. A relative URL that
begins with // (two slashes) always replaces everything from the hostname onwards.
These notations are best illustrated by example, in the following table. The table shows
relative URLs which are all assumed to have the base URL http://WebReference.com/html/,
and the absolute URLs that they translate into:
Relative URI Absolute URI
about.html http://WebReference.com/html/about.html
tutorial1/ http://WebReference.com/html/tutorial1/

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tutorial1/2.html http://WebReference.com/html/tutorial1/2.html
/ http://WebReference.com/
//www.internet.com/ http://www.internet.com/
/experts/ http://WebReference.com/experts/
../ http://WebReference.com/
../experts/ http://WebReference.com/experts/
../../../ http://WebReference.com/
./ http://WebReference.com/html/
./about.html http://WebReference.com/html/about.html
Table 2: Resolving relative URLs relative to http://WebReference.com/html/
OTHER URL SCHEMES
The mailto scheme
The mailto scheme is an example of an opaque URI scheme. Mailto URLs identify
someone's e-mail address. Their syntax is simple. You have the scheme name, the colon, and
then the e-mail address. If you're someone who has a thing for collecting e-mail addresses,
you might refer to yourself in the following ways:
mailto:stephanos@webreference.com
mailto:stephanos@internet.com
mailto:sp249@cam.ac.uk
mailto:spip@hol.gr
mailto:spip@mercator.nrcps.ariadne-t.gr
An important note here is that somewhere along the way someone came up with the brilliant
idea of including the subject of an e-mail in the URL, like this:
mailto:stephanos@webreference.com?subject=Feedback
URIs identifies resources, and don't do anything else. A program might process a
mailto URL by sending e-mail to the person, but it might do something else instead; add it to
your address book, add it to your kill file so you don't see his e-mail, or anything else. There
is also a second very important problem with the above syntax: a user agent that doesn't
understand it (and there are many) but does understand normal mailto syntax will try to send
mail to the address stephanos@webreference.com?subject=Feedback, which is not a valid e-
mail address. So even though you might see the above used some times in HTML, don't use
it. And if you want to do the world a favor, mail the person who did and tell them not to do it,
citing the reasons above.
The ftp scheme
The ftp scheme is very similar to the http scheme, and is used to locate files available
via FTP (File Transfer Protocol). The syntax is very similar to http syntax:
ftp://sunsite.unc.edu/pub/Linux/ls-lR.gz
The above URL points to the FTP server on sunsite.unc.edu, to the file ls-lR.gz in the
/pub/Linux directory. It is also possible to specify a username and optionally, a password for
the connection. The syntax is like this:

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ftp://user@host/path/file
ftp://user:password@host/path/file
Note that supplying a password like this is sometimes a bad idea. Some people might tell you
this is a huge security risk, but this is not really true: a URL like the one above is typed into
your browser will only be a risk if someone peeps over your shoulder and sees the password.
The password itself is transmitted unencrypted anyway, and can be intercepted in transit.
Before you go paranoid about this, remember that if your read your mail through POP (Post
Office Protocol), like most people do, then your mail password is also transmitted in the
clear. The lesson in this is that if you're going to be paranoid, at least do it for the right
reasons.
The file scheme
The file scheme is used to point to files on your computer. It is slightly tricky, because
(most) absolute file URLs aren't really absolute; they're always relative to your computer.
However, you can specify the hostname in a file URL. Remember that a URL just tells you
where a resource is located, not how to locate it. So this does make sense. If the hostname is
omitted, the current host is assumed. If a URL is encountered by a program with a hostname
that's different than the one it's working on, it will most likely decide that it cannot access the
file, but this has nothing to do with the URL itself. The syntax is again much like the http
syntax, only omitting the port numbers, like this:
file:///home/stephanos/public_html/myface.jpg
file://localhost/temp/install_log.txt
Note that the pathname here represents a path name in the local file system, so the slashes are
usually replaced by a more appropriate character before the file is accessed. UNIX uses
slashes, Windows uses backslashes, Macintosh and other operating systems use other
conventions.
The news scheme
The news scheme is another opaque URL scheme. It is used to refer to Usenet
newsgroups or specific messages within these newsgroups. It has two possible syntaxes. One
is the name of a Usenet newsgroup, and the other is the message id of a Usenet post. Note
that the message id must be entered without the usual angle brackets (< and >).
news:comp.infosystems.www.authoring.html
news:ba-ciwah-1998Jun4-013702@mud.stack.nl
news:*
The third example points to all available newsgroups and can be used to refer to Usenet in
general.
The telnet scheme
The telnet scheme has identical syntax to the ftp scheme, with the exception that there
is no pathname. Only a hostname, and optionally a port, username and password may be
supplied.
telnet://stephanos:secret@somehost.internet.com:35/

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The above indicates a telnet session for user "stephanos" with password "secret" on port 35 of
somehost.internet.com.
7. HTML tags.
Tag Description DTD
Basic
<!DOCTYPE> Defines the document type STF
<html> Defines an HTML document STF
<body> Defines the document's body STF
<h1> to <h6> Defines HTML headings STF
<p> Defines a paragraph STF
<br /> Inserts a single line break STF
<hr /> Defines a horizontal line STF
 Defines a comment STF
Formatting
<acronym> Defines an acronym STF
<abbr> Defines an abbreviation STF
<address> Defines contact information for the author/owner of a STF
<b> Defines bold text STF
<bdo> Overrides the current text direction STF
<big> Defines big text STF
<blockquote> Defines a long quotation STF
<center> Deprecated. Defines centered text TF
<cite> Defines a citation STF
<code> Defines a piece of computer code STF
<del> Defines text that has been deleted from a document STF
<dfn> Defines a definition term STF
<em> Defines emphasized text STF
<font> Deprecated. Defines font, color, and size for text TF
<i> Defines italic text STF
<ins> Defines text that has been inserted into a document STF
<kbd> Defines keyboard input STF
<pre> Defines preformatted text STF
<q> Defines a short quotation STF
<s> Deprecated. Defines strikethrough text TF
<samp> Defines sample output from a computer program STF
<small> Defines smaller text STF
<strike> Deprecated. Defines strikethrough text TF
<strong> Defines strong text STF
<sub> Defines subscripted text STF
<sup> Defines superscripted text STF

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<tt> Defines teletype text STF
<u> Deprecated. Defines underlined text TF
<var> Defines a variable STF
<xmp> Deprecated. Defines preformatted text
Forms
<form> Defines an HTML form for user input STF
<input /> Defines an input control STF
<textarea> Defines a multiline input control (text area) STF
<button> Defines a clickable button STF
<select> Defines a drop-down list STF
<optgroup> Defines a group of related options in a drop-down list STF
<option> Defines an option in a drop-down list STF
<label> Defines a label for an <input> element STF
<fieldset> Groups related elements in a form STF
<legend> Defines a caption for a <fieldset> element STF
Frames
<frame /> Defines a window (a frame) in a frameset F
<frameset> Defines a set of frames F
<noframes> Defines an alternate content for users that do not TF
<iframe> Defines an inline frame TF
Images
<img /> Defines an image STF
<map> Defines an image-map STF
<area /> Defines an area inside an image-map STF
Links
<a> Defines an anchor STF
<link />
Defines the relationship between a document and an
external resource
STF
Lists
<ul> Defines an unordered list STF
<ol> Defines an ordered list STF
<li> Defines a list item STF
<dir> Deprecated. Defines a directory list TF
<dl> Defines a definition list STF
<dt> Defines an item in a definition list STF
<dd> Defines a description of an item in a definition list STF
<menu> Deprecated. Defines a menu list TF
Tables
<table> Defines a table STF
<caption> Defines a table caption STF
<th> Defines a header cell in a table STF
<tr> Defines a row in a table STF

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<td> Defines a cell in a table STF
<thead> Groups the header content in a table STF
<tbody> Groups the body content in a table STF
<tfoot> Groups the footer content in a table STF
<col /> Defines attribute values for one or more columns in a STF
<colgroup> Defines a group of columns in a table for formatting STF
Styles
<style> Defines style information for a document STF
<div> Defines a section in a document STF
<span> Defines a section in a document STF
Meta Info
<head> Defines information about the document STF
<title> Defines the document title STF
<meta> Defines metadata about an HTML document STF
<base />
Specifies the base URL/target for all relative URLs in a
document
STF
<basefont />
Deprecated. Specifies a default color, size, or font for
all the text in a document
TF
Programming
<script> Defines a client-side script STF
<noscript>
Defines an alternate content for users that do not
support client-side scripts
STF
<applet> Deprecated. Defines an embedded applet TF
<object> Defines an embedded object STF
<param /> Defines a parameter for an object STF
8. HTML forms and frames.
HTML FORMS
HTML forms are used to pass data to a server. A form can contain input elements like
text fields, checkboxes, radio-buttons, submit buttons and more. A form can also contain
select lists, textarea, fieldset, legend, and label elements.
The <form> tag is used to create an HTML form:
<form>
.
input elements
.
</form>
HTML Forms - The Input Element

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The most important form element is the input element. The input element is used to
select user information. An input element can vary in many ways, depending on the type
attribute. An input element can be of type text field, checkbox, password, radio button,
submit button, and more.
The most used input types are described below.
Text Fields
<input type="text" /> defines a one-line input field that a user can enter text into:
<form>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" />
</form>
Note: The form itself is not visible. Also note that the default width of a text field is 20
characters.
Password Field
<input type="password" /> defines a password field:
<form>
Password: <input type="password" name="pwd" />
</form>
Note: The characters in a password field are masked (shown as asterisks or circles).
Radio Buttons
<input type="radio" /> defines a radio button. Radio buttons let a user select ONLY ONE of
a limited number of choices:
<form>
<input type="radio" name="sex" value="male" /> Male<br />
<input type="radio" name="sex" value="female" /> Female
</form>
Checkboxes
<input type="checkbox" /> defines a checkbox. Checkboxes let a user select ONE or MORE
options of a limited number of choices.
<form>
<input type="checkbox" name="vehicle" value="Bike" /> I have a bike<br />
<input type="checkbox" name="vehicle" value="Car" /> I have a car
</form>
Submit Button
<input type="submit" /> defines a submit button.

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A submit button is used to send form data to a server. The data is sent to the page
specified in the form's action attribute. The file defined in the action attribute usually does
something with the received input:
<form name="input" action="html_form_action.asp" method="get">
Username: <input type="text" name="user" />
<input type="submit" value="Submit" />
</form>
If you type some characters in the text field above, and click the "Submit" button, the
browser will send your input to a page called "html_form_action.asp". The page will show
you the received input.
HTML FRAMES
With frames, you can display more than one HTML document in the same browser
window. Each HTML document is called a frame, and each frame is independent of the
others.
The disadvantages of using frames are:
• Frames are not expected to be supported in future versions of HTML
• Frames are difficult to use. (Printing the entire page is difficult).
• The web developer must keep track of more HTML documents
The HTML frameset Element
The frameset element holds one or more frame elements. Each frame element can
hold a separate document. The frameset element states HOW MANY columns or rows there
will be in the frameset, and HOW MUCH percentage/pixels of space will occupy each of
them.
The HTML frame Element
The <frame> tag defines one particular window (frame) within a frameset.
In the example below we have a frameset with two columns.
The first column is set to 25% of the width of the browser window. The second column is set
to 75% of the width of the browser window. The document "frame_a.htm" is put into the first
column, and the document "frame_b.htm" is put into the second column:
<frameset cols="25%,75%">
<frame src="frame_a.htm" />
<frame src="frame_b.htm" />
</frameset>
Note: The frameset column size can also be set in pixels (cols="200,500"), and one of the
columns can be set to use the remaining space, with an asterisk (cols="25%,*").

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UNIT 2
1. What are Literals in JavaScript?
Literals are the way you represent values in JavaScript. These are fixed values that we
literally provide in your application source, and are not variables. Examples of literals
include:
42
3.14159
"To be or not to be"
Integers
Integers can be expressed in decimal (base 10), hexadecimal (base 16), or octal (base 8)
format. A decimal integer literal consists of a sequence of digits (optionally suffixed as
described below) without a leading 0 (zero). An integer can be expressed in octal or
hexadecimal rather than decimal. A leading 0 (zero) on an integer literal means it is in octal; a
leading 0x (or 0X) means hexadecimal. Hexadecimal integers can include digits (0-9) and the
letters a-f and A-F. Octal integers can include only the digits 0-7.
Floating Point Literals
A floating point literal can have the following parts: a decimal integer, a decimal point ("."), a
fraction (another decimal number), an exponent, and a type suffix. The exponent part is an
"e" or "E" followed by an integer, which can be signed (preceded by a "+" or "-"). A floating
point literal must have at least one digit, plus either a decimal point or "e" (or "E").
Some examples of floating point literals are:
3.1415
-3.1E12
.1e12
2E-12
Boolean Literals
The boolean type has two literal values: true and false.
String Literals
A string literal is zero or more characters enclosed in double (") or single (') quotes.
A string must be delimited by quotes of the same type; that is, either both single quotes or
double quotes. The following are examples of string literals:
"blah"
'blah'
"1234"
"one line n another line"
Special Characters
We can use the following special characters in JavaScript string literals:
b indicates a backspace.

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f indicates a a form feed.
n indicates a new line character.
r indicates a carriage return.
t indicates a tab character.
2. Describe JavaScript Variables and Data Types.
JavaScript Data Types:
One of the most fundamental characteristics of a programming language is the set of data
types it supports. These are the type of values that can be represented and manipulated in a
programming language. JavaScript allows working with three primitive data types:
Numbers eg. 123, 120.50 etc.
Strings of text e.g. "This text string" etc.
Boolean e.g. true or false.
JavaScript also defines two trivial data types, null and undefined, each of which defines only
a single value. In addition to these primitive data types, JavaScript supports a composite data
type known as object.
JavaScript Variables:
Like many other programming languages, JavaScript has variables. Variables can be thought
of as named containers. We can place data into these containers and then refer to the data
simply by naming the container. Before we use a variable in a JavaScript program, we must
declare it. Variables are declared with the var keyword as follows:
<script type="text/javascript">

</script>
We can also declare multiple variables with the same var keyword as follows:
script type="text/javascript">

</script>
3. Explain the CSS Box Model in detail.
All HTML elements can be considered as boxes. In CSS, the term "box model" is used when
talking about design and layout. The CSS box model is essentially a box that wraps around
HTML elements, and it consists of: margins, borders, padding, and the actual content. The
box model allows us to place a border around elements and space elements in relation to
other elements. The image below illustrates the box model:

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Explanation of the different parts:
Margin - Clears an area around the border. The margin does not have a background color,
it is completely transparent
Border - A border that goes around the padding and content. The border is affected by the
background color of the box
Padding - Clears an area around the content. The padding is affected by the background
color of the box
Content - The content of the box, where text and images appear
4. Describe the CSS Border Style Properties:
The border-style property can have from one to four values.
border-style: dotted solid double dashed;
o top border is dotted
o right border is solid
o bottom border is double
o left border is dashed
border-style: dotted solid double;
o top border is dotted
o right and left borders are solid
o bottom border is double
border-style: dotted solid;
o top and bottom borders are dotted
o right and left borders are solid
border-style: dotted;

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o all four borders are dotted
5. Explain CSS Text Properties?
Text Color
-The color property is used to set the color of the text. The color can be specified by:
Name – a color name, like “red”
RGB – an RGB value, like “rgb (255, 0, 0)”
Hex – a hex value, like “#ff0000”
-The default color for a page is defined in the body selector.
Text Alignment
-The text-align property is used to set the horizontal alignment of a text.
-Text can be centered, or aligned to the left or right, or justified.
-When text-align is set to “justify”, each line is stretched so that every line has equal width,
and the left and right margins are straight (like in magazines and newspapers).
Text Decoration
-The text-decoration property is used to set or remove decorations from text.
-The text-decoration property is mostly used to remove underlines from links for design
purposes:
Text Transformation
-The text-transform property is used to specify uppercase and lowercase letters in a text. It
can be used to turn everything into uppercase or lowercase letters, or capitalize the first letter
of each word.
Text Indentation
-The text-indentation property is used to specify the indentation of the first line of a text.
6. Explain in details about CSS.
CSS stands for Cascading Style Sheets. Styles define how to display HTML elements. Styles
were added to HTML 4.0 to solve a problem. External Style Sheets can save a lot of work.
External Style Sheets are stored in CSS files.
CSS Syntax
A CSS rule has two main parts: a selector, and one or more declarations:

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The selector is normally the HTML element you want to style. Each declaration consists of a
property and a value. The property is the style attribute you want to change. Each property
has a value.
CSS Example
A CSS declaration always ends with a semicolon, and declaration groups are surrounded by
curly brackets:
p {color:red;text-align:center;}
To make the CSS more readable, you can put one declaration on each line, like this:
Example
p
{
color:red;
text-align:center;
}
CSS Comments
Comments are used to explain your code, and may help you when you edit the source code at
a later date. Comments are ignored by browsers.
A CSS comment begins with "/*", and ends with "*/", like this:
/*This is a comment*/
p
{
text-align:center;
/*This is another comment*/
color:black;
font-family:arial;
}
CSS Id and Class
The id and class Selectors
In addition to setting a style for a HTML element, CSS allows you to specify your own
selectors called "id" and "class".
The id Selector
The id selector is used to specify a style for a single, unique element. The id selector uses the
id attribute of the HTML element, and is defined with a "#". The style rule below will be
applied to the element with id="para1":

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Example
#para1
{
text-align:center;
color:red;
}
The class Selector
The class selector is used to specify a style for a group of elements. Unlike the id selector, the
class selector is most often used on several elements. This allows you to set a particular style
for many HTML elements with the same class. The class selector uses the HTML class
attribute, and is defined with a "." In the example below, all HTML elements with
class="center" will be center-aligned:
Example
.center {text-align:center;}
In the example below, all p elements with class="center" will be center-aligned:
Example
p.center {text-align:center;}
CSS How To...
When a browser reads a style sheet, it will format the document according to it.
Three Ways to Insert CSS
There are three ways of inserting a style sheet:
External style sheet
Internal style sheet
Inline style
External Style Sheet
An external style sheet is ideal when the style is applied to many pages. With an external
style sheet, you can change the look of an entire Web site by changing one file. Each page
must link to the style sheet using the <link> tag. The <link> tag goes inside the head section:
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css" />
</head>
An external style sheet can be written in any text editor. The file should not contain any html
tags. Your style sheet should be saved with a .css extension. An example of a style sheet file
is shown below:

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hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
Do not leave spaces between the property value and the unit (such as margin-left:20 px).
Correct way: margin-left:20px
Internal Style Sheet
An internal style sheet should be used when a single document has a unique style. You define
internal styles in the head section of an HTML page, by using the <style> tag, like this:
<head>
<style type="text/css">
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
</style>
</head>
Inline Styles
An inline style loses many of the advantages of style sheets by mixing content with
presentation. To use inline styles you use the style attribute in the relevant tag. The style
attribute can contain any CSS property. The example shows how to change the color and the
left margin of a paragraph:
<p style="color:sienna;margin-left:20px">This is a paragraph.</p>
Multiple Style Sheets
If some properties have been set for the same selector in different style sheets, the values will
be inherited from the more specific style sheet.
For example, an external style sheet has these properties for the h3 selector:
h3
{
color:red;
text-align:left;
font-size:8pt;
}
And an internal style sheet has these properties for the h3 selector:
h3
{
text-align:right;
font-size:20pt;
}
If the page with the internal style sheet also links to the external style sheet the properties for
h3 will be:

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color:red;
text-align:right;
font-size:20pt;
The color is inherited from the external style sheet and the text-alignment and the font-size is
replaced by the internal style sheet.
Multiple Styles Will Cascade into One
Styles can be specified:
inside an HTML element
inside the head section of an HTML page
in an external CSS file
Tip: Even multiple external style sheets can be referenced inside a single HTML document.
Cascading order
Generally speaking we can say that all the styles will "cascade" into a new "virtual" style
sheet by the following rules, where number four has the highest priority:
Browser default
External style sheet
Internal style sheet (in the head section)
Inline style (inside an HTML element)
7. Explain about JavaScript.
JavaScript is the most popular scripting language on the internet, and works in all major
browsers, such as Internet Explorer, Firefox, Chrome, Opera, and Safari.
JavaScript was designed to add interactivity to HTML pages. JavaScript is a scripting
language. A scripting language is a lightweight programming language. JavaScript is usually
embedded directly into HTML pages. JavaScript is an interpreted language. Everyone can use
JavaScript without purchasing a license.
Java and JavaScript are two completely different languages in both concept and design. Java
(developed by Sun Microsystems) is a powerful and much more complex programming
language - in the same category as C and C++.
JavaScript gives HTML designers a programming tool - HTML authors are normally not
programmers, but JavaScript is a scripting language with a very simple syntax! Almost
anyone can put small "snippets" of code into their HTML pages. JavaScript can react to
events - A JavaScript can be set to execute when something happens, like when a page has
finished loading or when a user clicks on an HTML element. JavaScript can read and write
HTML elements - A JavaScript can read and change the content of an HTML element
JavaScript can be used to validate data - A JavaScript can be used to validate form data
before it is submitted to a server. This saves the server from extra processing. JavaScript can
be used to detect the visitor's browser - A JavaScript can be used to detect the visitor's

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browser, and - depending on the browser - load another page specifically designed for that
browser. JavaScript can be used to create cookies - A JavaScript can be used to store and
retrieve information on the visitor's computer
JavaScript = ECMAScript
JavaScript is an implementation of the ECMAScript language standard. ECMA-262 is the
official JavaScript standard. JavaScript was invented by Brendan Eich at Netscape (with
Navigator 2.0), and has appeared in all browsers since 1996. The official standardization was
adopted by the ECMA organization (an industry standardization association) in 1997. The
ECMA standard (called ECMAScript-262) was approved as an international ISO (ISO/IEC
16262) standard in 1998. The development is still in progress.
JavaScript How To
The HTML <script> tag is used to insert a JavaScript into an HTML page.
Writing to The HTML Document
The example below writes a <p> element with current date information to the HTML
document:
Example
<html>
<body>
<h1>My First Web Page</h1>
document.write("<p>" + Date() + "</p>");
</script>
</body>
</html>
Note: Try to avoid using document.write() in real life JavaScript code. The entire HTML
page will be overwritten if document.write() is used inside a function, or after the page is
loaded. However, document.write() is an easy way to demonstrate JavaScript output in a
tutorial.
Changing HTML Elements
The example below writes the current date into an existing <p> element:
Example
<html>
<body>
<p id="demo"></p>
document.getElementById("demo").innerHTML=Date();

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</script>
</body>
</html>
Note: To manipulate HTML elements JavaScript uses the DOM method getElementById().
This method accesses the element with the specified id.
Examples Explained
To insert a JavaScript into an HTML page, use the <script> tag. Inside the <script> tag use
the type attribute to define the scripting language. The <script> and </script> tells where the
JavaScript starts and ends:
<html>
<body>
<p id="demo">This is a paragraph.</p>
... some JavaScript code ...
</script>
</body>
</html>
The lines between the <script> and </script> contain the JavaScript and are executed by the
browser. In this case the browser will replace the content of the HTML element with
id="demo", with the current date:
<html>
<body>
<p id="demo">This is a paragraph.</p>
</script>
</body>
</html>
Without the <script> tag(s), the browser will treat
"document.getElementById("demo").innerHTML=Date();" as pure text and just write it to
the page:
Some Browsers do Not Support JavaScript
Browsers that do not support JavaScript will display JavaScript as page content. To prevent
them from doing this, and as a part of the JavaScript standard, the HTML comment tag
should be used to "hide" the JavaScript. Just add an HTML comment tag  (end of comment) after the last JavaScript statement, like this:
<html>

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<body>

</script>
</body>
</html>
The two forward slashes at the end of comment line (//) is the JavaScript comment symbol.
This prevents JavaScript from executing the --> tag.
JavaScript Where To
JavaScripts can be put in the <body> and in the <head> sections of an HTML page.
JavaScript in <body>. The example below writes the current date into an existing <p>
element when the page loads:
Example
<html>
<body>
<p id="demo"></p>
</script>
</body>
</html>
Note that the JavaScript is placed at the bottom of the page to make sure it is not executed
before the <p> element is created.
JavaScript Functions and Events
JavaScripts in an HTML page will be executed when the page loads. This is not always what
we want. Sometimes we want to execute a JavaScript when an event occurs, such as when a
user clicks a button. When this is the case we can put the script inside a function. Events are
normally used in combination with functions (like calling a function when an event occurs).
You will learn more about JavaScript functions and events in later chapters.
JavaScript in <head>
The example below calls a function when a button is clicked:
Example
<html>
<head>
function displayDate()

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{
}
</script>
</head>
<body>
<p id="demo"></p>
<button type="button" onclick="displayDate()">Display Date</button>
</body>
</html>
Scripts in <head> and <body>
You can place an unlimited number of scripts in your document, and you can have scripts in
both the body and the head section at the same time. It is a common practice to put all
functions in the head section, or at the bottom of the page. This way they are all in one place
and do not interfere with page content.
Using an External JavaScript
JavaScript can also be placed in external files. External JavaScript files often contain code to
be used on several different web pages. External JavaScript files have the file extension .js.
Note: External script cannot contain the <script></script> tags!
To use an external script, point to the .js file in the "src" attribute of the <script> tag:
Example
<html>
<head>
<script type="text/javascript" src="xxx.js"></script>
</head>
<body>
</body>
</html>
8. Java script variables and operators.
JavaScript Variables
Variables are "containers" for storing information. JavaScript variables are used to hold
values or expressions. A variable can have a short name, like x, or a more descriptive name,
like carname.
Rules for JavaScript variable names:
• Variable names are case sensitive (y and Y are two different variables)

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• Variable names must begin with a letter, the $ character, or the underscore character
Example
A variable's value can change during the execution of a script. You can refer to a variable by
its name to display or change its value.
Declaring (Creating) JavaScript Variables
Creating variables in JavaScript is most often referred to as "declaring" variables. You
declare JavaScript variables with the var keyword:
var x;
var carname;
After the declaration shown above, the variables are empty (they have no values yet).
However, you can also assign values to the variables when you declare them:
var x=5;
var carname="Volvo";
After the execution of the statements above, the variable x will hold the value 5, and carname
will hold the value Volvo.
Local JavaScript Variables
A variable declared within a JavaScript function becomes LOCAL and can only be accessed
within that function. (The variable has local scope). You can have local variables with the
same name in different functions, because local variables are only recognized by the function
in which they are declared. Local variables are deleted as soon as the function is completed.
Global JavaScript Variables
Variables declared outside a function become GLOBAL, and all scripts and functions on the
web page can access it. Global variables are deleted when you close the page.
Assigning Values to Undeclared JavaScript Variables
If you assign values to variables that have not yet been declared, the variables will
automatically be declared as global variables.
These statements:
x=5;
carname="Volvo";
will declare the variables x and carname as global variables (if they don't already exist).
JavaScript Arithmetic
As with algebra, you can do arithmetic operations with JavaScript variables:

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y=x-5;
z=y+5;
You will learn more about the operators that can be used in the next chapter of this tutorial.
JavaScript Operators
= is used to assign values.
+ is used to add values.
The assignment operator = is used to assign values to JavaScript variables. The arithmetic
operator + is used to add values together.
y=5;
z=2;
x=y+z;
The value of x, after the execution of the statements above, is 7.
JavaScript Arithmetic Operators
Arithmetic operators are used to perform arithmetic between variables and/or values. Given
that y=5, the table below explains the arithmetic operators:
Operator Description Example Result
+ Addition x=y+2 x=7 y=5
- Subtraction x=y-2 x=3 y=5
* Multiplication x=y*2 x=10 y=5
/ Division x=y/2 x=2.5 y=5
% Modulus x=y%2x=1 y=5
++ Increment x=++y x=6 y=6
x=y++ x=5 y=6
-- Decrement x=--y x=4 y=4
x=y-- x=5 y=4
JavaScript Assignment Operators
Assignment operators are used to assign values to JavaScript variables. Given that x=10 and
y=5, the table below explains the assignment operators:
Operator Example Same As Result
= x=y x=5
+= x+=y x=x+y x=15
-= x-=y x=x-y x=5
*= x*=y x=x*y x=50
/= x/=y x=x/y x=2
%= x%=y x=x%y x=0
The + Operator Used on Strings
The + operator can also be used to add string variables or text values together. To add two or
more string variables together, use the + operator.

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txt1="What a very";
txt2="nice day";
txt3=txt1+txt2;
After the execution of the statements above, the variable txt3 contains "What a verynice day".
To add a space between the two strings, insert a space into one of the strings:
txt1="What a very ";
txt2="nice day";
txt3=txt1+txt2;
or insert a space into the expression:
txt1="What a very";
txt2="nice day";
txt3=txt1+" "+txt2;
After the execution of the statements above, the variable txt3 contains:
"What a very nice day"
Adding Strings and Numbers
The rule is: If you add a number and a string, the result will be a string!
Example
x=5+5;
document.write(x);
x="5"+"5";
document.write(x);
x=5+"5";
document.write(x);
x="5"+5;
document.write(x);

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UNIT 3
1. Design a web page to detect the visitor’s browser name and version?
<html>
<body>
document.write("Browser CodeName: " + navigator.appCodeName);
document.write("<br /><br />");
document.write("Browser Name: " + navigator.appName);
document.write("Browser Version: " + navigator.appVersion);
document.write("Cookies Enabled: " + navigator.cookieEnabled);
document.write("Platform: " + navigator.platform);
document.write("User-agent header: " + navigator.userAgent);
</script>
</body>
</html>
2. Describe Cookies in detail.
Cookies are used to store an ID for a shopping session with each subsequent connection, and
can look up the current session ID and then use that ID to extract information about that
session from a lookup table on the server machine. So, there would really be two tables: one
that associates session IDs with user tables, and the user tables themselves that store user-
specific data. For example, on the initial request a servlet could do something like the
following:
String sessionID = makeUniqueString();
HashMap sessionInfo = new HashMap();
HashMap globalTable = findTableStoringSessions();
globalTable.put(sessionID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sessionID);
sessionCookie.setPath("/");
response.addCookie(sessionCookie);
In later requests the server could use the global Table hash table to associate a session id from
the jsessionid cookie with the session Info hash table of user-specific data. Using cookies in
this manner is an excellent solution and is the most widely used approach for session
handling. it is nice that Servlets have a higher-level API that handles all this plus the
following tedious tasks:
• Extracting the cookie that stores the session identifier from the other cookies (there may be
many cookies, after all).
• Determining when idle sessions have expired, and reclaiming them.
• Associating the hash tables with each request.

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• Generating the unique session identifiers.
3. Explain Sessions in detail?
Sessions in servlets is straightforward and involves four basic steps.
1. Accessing the session object associated with the current request.
-Call request.getSession to get an HttpSession object, which is a simple hash table for storing
user-specific data.
2. Looking up information associated with a session.
-Call getAttribute on the HttpSession object, cast the return value to the appropriate type, and
check whether the result is null.
3. Storing information in a session.
-Use setAttribute with a key and a value.
4. Discarding session data.
-Call removeAttribute to discard a specific value. Calls invalidate to discard an entire session.
Call logout to log the client out of the Web server and invalidate all sessions associated with
that user.
Accessing the Session Object Associated with the Current Request
Session objects are of type HttpSession, but they are basically just hash tables that can store
arbitrary user objects (each associated with a key). The HttpSession object can be
implemented by calling the getSession method of HttpServletRequest, as below.
HttpSession session = request.getSession();
4. Explain URL Rewriting?
URL Rewriting:
-URL rewriting is another way to support anonymous session tracking. ie,If the browser does
not support cookies, URL rewriting provides with another session tracking alternative.
-With URL rewriting, every local URL the user might click on is dynamically modified, or
rewritten, to include extra information.
-The extra information can be in the form of extra path information, added parameters, or
some custom, server-specific URL change.
-Due to the limited space available in rewriting a URL, the extra information is usually
limited to a unique session ID.
Example:

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For example, the following URLs have been rewritten to pass the session ID 123:
http://server:port/servlet/Rewritten original
http://server:port/servlet/Rewritten/123 extra path information
http://server:port/servlet/Rewritten?sessionid=123 added parameter
http://server:port/servlet/Rewritten;$sessionid$123 custom change
Advantages:
1. URL rewriting works for all dynamically created documents servlet.
2. Custom URL rewriting can even work for static documents with the right server support.
Disadvantages:
1. Using extra path information works on all servers, and it works as a target for forms that
use both the GET and POST methods. It doesn't work well if a servlet has to use the extra
path information as true path information.
2. Using an added parameter works on all servers too, but it fails as a target for forms that use
the POST method, and it can cause parameter naming collisions.
3. Using a custom, server-specific change works under all conditions for servers that support
the change. Unfortunately, it doesn't work at all for servers that don't support the change.
5. Explain about JavaScript global function?
parseInt(x, [radix])
Parses any string "x" and returns the first valid number (integer) it encounters.
If the first character in the string is not a number, white spaces, or a leading minus sign,
parseInt() returns NaN instead. You can test for NaN using the isNaN() function below.
parseInt() supports an optional 2nd "radix" parameter to specify the base of the number to
be parsed (valid range is 2-36).
Entering "10" would parse the number in the familiar decimal system, while "16" would be
hexadecimal.
Without this parameter present, parseInt() assumes any number that begins with "0x" to be
radix 16, "0" to be radix 8, and any other number to be radix 10.
Examples:
parseInt("3 chances") //returns 3
parseInt("I have 3 computers") //returns NaN
parseInt("17", 8) //returns 15
parseFloat(x)
Parses any string "x" and returns the first valid floating point number it encounters. Use
this function to extract numbers with decimals, for example.
If the first character in the string is not a number, white spaces, or a leading minus sign,
parseFloat() returns NaN instead. You can test for NaN using the isNaN() function below.
Example:
parseFloat("-3.98 points") //returns -3.98

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6. Explain in detail about DOM.
The DOM is a W3C (World Wide Web Consortium) standard. The DOM defines a standard
for accessing documents like HTML and XML: "The W3C Document Object Model (DOM)
is a platform and language-neutral interface that allows programs and scripts to dynamically
access and update the content, structure, and style of a document."
The DOM is separated into 3 different parts / levels:
• Core DOM - standard model for any structured document
• XML DOM - standard model for XML documents
• HTML DOM - standard model for HTML documents. The DOM defines the objects
and properties of all document elements, and the methods (interface) to access them.
What is the XML DOM?
The XML DOM defines the objects and properties of all XML elements, and the methods
(interface) to access them.
What is the HTML DOM?
The HTML DOM is:
A standard object model for HTML. A standard programming interface for HTML. Platform-
and language-independent. The HTML DOM defines the objects and properties of all HTML
elements, and the methods (interface) to access them. In other words: The HTML DOM is a
standard for how to get, change, add, or delete HTML elements.
DOM Nodes
According to the DOM, everything in an HTML document is a node. The DOM says: The
entire document is a document node. Every HTML element is an element node. The texts in
the HTML elements are text nodes. Every HTML attribute is an attribute node. Comments
are comment nodes
DOM Example
Look at the following HTML document:
<html>
<head>
<title>DOM Tutorial</title>
</head>
<body>
<h1>DOM Lesson one</h1>
<p>Hello world!</p>
</body>
</html>
The root node in the HTML above is <html>. All other nodes in the document are contained
within <html>.

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The <html> node has two child nodes; <head> and <body>. The <head> node holds a <title>
node. The <body> node holds a <h1> and <p> node.
Text is Always Stored in Text Nodes
A common error in DOM processing is to expect an element node to contain text. However,
the text of an element node is stored in a text node. In this example: <title>DOM
Tutorial</title>, the element node <title>, holds a text node with the value "DOM Tutorial".
However, in the HTML DOM the value of the text node can be accessed by the innerHTML
property.
The HTML DOM Node Tree
The HTML DOM views an HTML document as a tree-structure. The tree structure is called a
node-tree. All nodes can be accessed through the tree. Their contents can be modified or
deleted, and new elements can be created. The node tree below shows the set of nodes, and
the connections between them. The tree starts at the root node and branches out to the text
nodes at the lowest level of the tree:
Node Parents, Children, and Siblings
The nodes in the node tree have a hierarchical relationship to each other. The terms parent,
child, and sibling are used to describe the relationships. Parent nodes have children. Children
on the same level are called siblings (brothers or sisters). In a node tree, the top node is called
the root. Every node, except the root, has exactly one parent node. A node can have any
number of children. A leaf is a node with no children. Siblings are nodes with the same
parent. The following image illustrates a part of the node tree and the relationship between
the nodes:

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Look at the following HTML fragment:
<html>
<head>
<title>DOM Tutorial</title>
</head>
<body>
<h1>DOM Lesson one</h1>
<p>Hello world!</p>
</body>
</html>
From the HTML above:
The <html> node has no parent node; it is the root node. The parent node of the <head> and
<body> nodes is the <html> node. The parent node of the "Hello world!" text node is the <p>
node and:
The <html> node has two child nodes; <head> and <body>
The <head> node has one child node; the <title> node
The <title> node also has one child node; the text node "DOM Tutorial"
The <h1> and <p> nodes are siblings, and both child nodes of <body>
First Child - Last Child
From the HTML above:
The <head> element is the first child of the <html> element, and the <body> element is the
last child of the <html> element. The <h1> element is the first child of the <body> element,
and the <p> element is the last child of the <body> element
7. Explain in details about Servlet with example.
A Servlet is a java based server side web technology. As the name implies, it serves a client
request and receives a response from the server. Technically speaking a Servlet is a Java class

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in Java EE that conforms to the Java Servlet API, a protocol by which a Java class may
respond to requests. They are not tied to a specific client-server protocol, but are most often
used with the HTTP protocol. Therefore, the word "Servlet" is often used in the meaning of
"HTTP Servlet".[2] Thus, a software developer may use a servlet to add dynamic content to a
Web server using the Java platform. The generated content is commonly HTML, but may be
other data such as XML. Servlets are the Java counterpart to non-Java dynamic Web content
technologies such as CGI and ASP.NET. Servlets can maintain state in session variables
across many server transactions by using HTTP cookies, or URL rewriting.
To deploy and run a Servlet, a Web container must be used. A Web container (also known as
a Servlet container) is essentially the component of a Web server that interacts with the
servlets. The Web container is responsible for managing the lifecycle of servlets, mapping a
URL to a particular servlet and ensuring that the URL requester has the correct access rights.
The servlet API, contained in the Java package hierarchy javax.servlet, defines the expected
interactions of the Web container and a servlet.
A Servlet is an object that receives a request and generates a response based on that request.
The basic servlet package defines Java objects to represent servlet requests and responses, as
well as objects to reflect the servlet's configuration parameters and execution environment.
The package javax.servlet.http defines HTTP-specific subclasses of the generic servlet
elements, including session management objects that track multiple requests and responses
between the Web server and a client. Servlets may be packaged in a WAR file as a Web
application.
Servlets can be generated automatically from JavaServer Pages (JSP) by the JavaServer
Pages compiler. The difference between Servlets and JSP is that Servlets typically embed
HTML inside Java code, while JSPs embed Java code in HTML. While the direct usage of
Servlets to generate HTML (as shown in the example below) has become rare, the higher
level MVC web framework in Java EE (JSF) still explicitly uses the Servlet technology for
the low level request/response handling via the FacesServlet. A somewhat older usage is to
use servlets in conjunction with JSPs in a pattern called "Model 2", which is a flavor of the
model-view-controller pattern. A servlet is a Java component that can be plugged into a Java-
enabled web server to provide custom services. These services can include:
New features
Runtime changes to content
Runtime changes to presentation
New standard protocols (such as FTP)
New custom protocols
Advantages over CGI
The advantages of using Servlets are their fast performance and ease of use combined with
more power over traditional CGI (Common Gateway Interface). Traditional CGI scripts
written in Java have a number of disadvantages when it comes to performance:
When an HTTP request is made, a new process is created for each call of the CGI script. This
overhead of process creation can be very system-intensive, especially when the script does
relatively fast operations. Thus, process creation will take more time than CGI script
execution. Java Servlets solve this, as a Servlet is not a separate process. Each request to be

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handled by a Servlet is handled by a separate Java thread within the Web server process,
omitting separate process forking by the HTTP daemon.
Simultaneous CGI request causes the CGI script to be copied and loaded into memory as
many times as there are requests. However, with Servlets, there are the same amount of
threads as requests, but there will only be one copy of the Servlet class created in memory
that stays there also between requests.
Only a single instance answers all requests concurrently. This reduces memory usage and
makes the management of persistent data easy.
A Servlet can be run by a Servlet engine in a restrictive environment, called a sandbox. This
is similar to an applet that runs in the sandbox of the Web browser. This makes a restrictive
use of potentially harmful Servlets possible.
Life cycle of a Servlet
During initialization stage of the Servlet life cycle, the web container initializes the Servlet
instance by calling the init() method. The container passes an object implementing the
ServletConfig interface via the init() method. This configuration object allows the Servlet to
access name-value initialization parameters from the web application.
After initialization, the Servlet can service client requests. Each request is serviced in its own
separate thread. The Web container calls the service() method of the Servlet for every
request. The service() method determines the kind of request being made and dispatches it to
an appropriate method to handle the request. The developer of the Servlet must provide an
implementation for these methods. If a request for a method that is not implemented by the
Servlet is made, the method of the parent class is called, typically resulting in an error being
returned to the requester.
Finally, the Web container calls the destroy() method that takes the Servlet out of service.
The destroy() method, like init(), is called only once in the lifecycle of a Servlet. Three
methods are central to the life cycle of a Servlet. These are init( ), service( ), and destroy( ).
They are implemented by every Servlet and are invoked at specific times by the server. Let us
consider a typical user scenario to understand when these methods are called.
Assume that a user enters a Uniform Resource Locator (URL) to a web browser.
• The browser then generates an HTTP request for this URL.
• This request is then sent to the appropriate server.
• The HTTP request is received by the web server.
• The server maps this request to a particular Servlet.
• The Servlet is dynamically retrieved and loaded into the address space of the server.
• The server invokes the init() method of the Servlet.
• This method is invoked only when the Servlet is first loaded into memory.
• It is possible to pass initialization parameters to the Servlet so it may configure itself.
• The server invokes the service() method of the Servlet.
• This method is called to process the HTTP request.

Notes e commerce

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Notes e commerce