Monday, August 5, 2013

Introduction to HTML

HTML

HTML stands for Hyper Text Markup Language.(The markup is the instructions for displaying or printing the text.)
HTML is not a programming languages but it is a markup language.
A markup language is a set of markup tags.
HTML uses markup tags to describe web pages.
It is a descriptive markup language that describes the structure and behavior of a web documents.
HTML was created by Tim Berners-Lee
HTML is a set of code that can be embedded in text to add formatting and linking information.
It allows these different kinds of data to be displayed together.
HTML is nothing more than a plain text file that allows for the inclusion of two kinds of text:

The Content

Text or information to be displayed or played back on the client’s screen.

The Markup

Text or information to control the display or to point to other information items in need of display .

HTML TAGS

Tags are the instructions that are embedded directly into the text of the document.
An HTML tag is a signal to the browser that it should do something other than just throw text up on the screen.
By conventional all HTML tags begin with an open an angle bracket(<) and end with close angle bracket(>).
HTML is specified as TAGs in an HTML document(i.e. Web Page)
There are two types of HTML tags:

Paired Tags
Singular Tags( stand-alone tags/ unpaired tags)

Paired Tags

A tag is said to be a paired tag if the text is placed between a tag and its companion tag.
In paired tags, the first tag is referred to as opening tag and the second tag is referred to as closing tag.

Example:

<i>Welcome</i>
Here, <i> is called opening tag and </i> is called a closing tag

Here are some more examples

<html>
<head>
<title>
<body>
<p>
<h#>
<address>
<nobr>
<center>
<block quote>
<pre>
<font>
<strike>
<b>
<i>
<big>
<small>
<sub>
<sup>
<u>
<lists>
<div>
<strong>

Singular tag

A Singular tag does not have a companion tag.
Singular tags are also known as unpaired tags or Stand-Alone tags.

Example:

<br>
<hr>

This tags does not require any companion tag.

<doctype>
<br>
<hr>
<basefont>
<meta>

HTML Tag

Some HTML tags require additional information to be supplied to them.

For example:-

When a picture is placed on the screen, information like the height and the width of the picture can be specified.

Additional information supplied to an HTML tag is known as Attributes of a Tag.
Attributes are written immediately following the tag, separated by a space.

<table border="1">

Multiple attributes can be associated with a tag, also separated by space.

HTML document

An HTML document contains two distinct parts:
The head
The body.
The head contains information about the document that is not displayed on the screen.
The body contains everything else that is displayed as part of the web of page

<HTML>

<HEAD>

…………..

<!-- header information & it is not displayed on the page

</HEAD>

<BODY>

…………..

<!-- all the HTML for display>

</BODY>

</HTML>

Head Eement

<HEAD> contains general information, or meta-information, about the document.
The head of the HTML document is an unordered collection of information about the document.
The main head element is a <TITLE> tag.
The contents of the <HEAD> are not displayed as part of the document text
It is just written after the <HTML> tag.

<TITLE>
<BASE>
<ISINDEX>
<NEXTID>
<LINK>
<META>
<STYLE>
<SCRIPT>

Title Element

The title of a document is specified by the TITLE element.
The TITLE element should occur in the HEAD of the document.
There may be only one title in any document.
It should identify the content of the document.
The <TITLE> element is not part of the body text, it is displayed in the window title.
It may not contain anchors, paragraph or any highlighting or other HTML Tag.
The title may be used to identify the node in a history list.
Your title should be descriptive but short, less than 64 characters.

Body Element

It specifies the main content of the document.
Body tag is placed immediately after the closing head tag(</Head>) and before any image or text included in the document.
The body of the HTML document contains all the text and images that make up the page together with all the HTML elements that provide the control or formatting of the page.
It is possible to control the document color scheme and background by specifying certain attributes in the <BODY ….> declaration.

Attributes are

used to point to an image file
BgColor: allow settings of background color
Text: used to change the text color

For Additional Quarries Please put Your Valuable Comment (!)

Electronic Journal

ELECTRONIC JOURNAL

Define as the journal that may take two different forms:
Journal that published in print form or digital form
Electronic –only journal, which is produced, published and distributed via electronic medium.

Advantages

Instant access
Issues can be unbundled.
Issues are directly loadable into an electronic database.
Proofreading can be done by authors
Electronic storage is more efficient than that for print volumes.
Paperless, but it has to be recognized that readers may want a printout of the articles they are interested in.

Disadvantages

Hardware and software are required
Training
Peer review is less common
Graphics are problematic
Copyright is undecided.
Archives(records) are hard to maintain

Types of Electronic Journal

Types of electronic journal may be classified in various way such as:

By location
By products
By Availability of print products
By Types of Technology Applied
By Price
By Peer Review

Characteristics

Limited Cost
Global Distribution
Very Satisfactory Quality of Reproduction of Image
Electronic subscription and sending in of articles
Personalized Subscription
Possibility of reliable analysis of readership
Use of hypertext
Digital Storage
Good Communication between the author and reader
Commercial Independence

LISTSERVE || NEWSGROUPS || TELNET || GOPHER || VERONICA || WAIS

LISTSERVE

First electronic mailing list software application, consisting of a set of email addresses for a group in which the sender can send one email and it will reach a variety of people.
Also called “distribution lists” or “discussion forums”
Lists of users hold a discussion about a particular subject.
Distribution lists are free and very satisfactory
This system is one of those with easiest access via the Internet, since it only requires the ability to send e-mail.
There are two types of distribution lists:

Moderated-The lists maintained by a single person, whose active participation is necessary for maintaining the list. This type is sometimes called a mailing list. The owner may edit the message in this type.
Unmoderated- The lists that do not require the intervention of anybody, to be maintained, since all the messages are managed by software, which does all the work. This type is called Listserve.

Advantages Of Listserve

Information exchange
Does not require full access to the Internet.
Great independence to the user.

There are major four listservers which provides distribution lists:

ListServe
Listprocessor
Majordomo
Mailbase

NEWSGROUPS

Worldwide system for the electronic exchange of news and views on a particular topic.
Also referred to as Usenet News.
Usenet is a discussion forum similar to distribution lists.
On the Usenet the messages are stored on notice board rather than distribution.
You do not need to subscribe to a newsgroup.
To participate in global distributed discussion system you must have the following facilities:
Your Internet provider must offer a “news feed” service
You must have a client on your computer that can interpret data sent from an NNTP server. This will take the form of a dedicated newsreader, or your web browser if it has been “news enabled

TELNET(TELETYPE NETWORK)

Telnet is a protocol that is most commonly used to log into a remote computer.
Telnet act as a terminal emulator.
Telnet is the protocol that enables one computer to connect to other computer. This process is also referred to as remote login.
The user’s computer which initiates the connection is referred to as the local computer.
The machine being connected to which accepts the connection is referred to as remote or host computer.
Once connected, the user’s computer emulates the remote computer. When the user types in commands, they are executed on the remote computer.
Telnet environment is based on text, as it does not support the graphical interface.
To get access via Telnet, you need an access code

#Using Telnet, you can

Send email
Download source code from websites
Send unexpected input to web servers that can give you amazing and illegal results.
Give arbitrary(random) input to many other services on Internet host computers
Probe the services offered by servers, routers and even people’s home computers.

#There are two ways of using the Telnet tool:

The input mode

Input mode allows you to establish the connection and use the remote computer

The command mode

Command mode is used to set the parameters to Telnet

GOPHER

It is a hierarchical menu-based system for exploring the Internet.
Gopher is a protocol designed to search, retrieve and display documents from remote sites on the Internet.
Originally Gopher had text based interface then it has evolved greatly, becoming a tool for obtaining multimedia data.
You can access Gopher by means of Telnet, although the menu options cannot be selected with the mouse.
Information accessible via gopher is stored on many coputers all over the Internet. These computers are called gopher servers.
Servers do not just contain a files, directories and searchable databases, they can also contain references to other servers.
To retrieve and search this information, you need to run a gopher client application on your computer.
Information stored on many kinds of non-gopher servers is also available via special gopher servers that act as gateways.
Gopher was created as a piece of software to utilize some of the services that were becoming available on the Internet.
It was designed to work with a variety of different Internet stand alone services.

Characteristics

Ease of use with user interface based on menus
It offers the possibility of discovering sources of information on the Internet without needing to know their location.
Gopher server automatically directs the search to the address, where what you want to see is stored.

VERONICA

Veronica is a tool which simplifies the search for resources in Gopher.
Veronica comes from “Very Easy Rodent Oriented Networked Index of Computerized Archives”
Veronica starts the search on the Gopher menus, from which you select “GOPHER-space search” or the name veronica, by keying in a keyword.
It gives you Gopher addresses with the keyword on their menus.
You can choose which of these sources in order to enter them.
While searching following things must be in consideration:
Search is not case sensitive
Veronica does not carry out searches in the complete text of the resources available on the Internet.

Types of Search Using VERONICA

Searching GOPHER space by keywords in titles- This type locates all types of resources that have title containing the keyword.
Searching GOPHER directories only for keywords in titles- It searches only for directories in which the keyword is contained in the title.
Simplified Veronica- When you select the option, veronica asks you for the keyword or words you want, together with additional information to control the search:

Simple search
Search by more than one keyword
Search for word roots
Search by types of Gopher
Specification of the number of resources analyzed

WAIS(WIDE AREA INFORMATION SERVERS)

It is a tool designed to search for information on the Internet by means of the keyword and provide as a result a list of the resources related to the keyword, ordering them according to the number of times the keyword appears in the document.
WAIS searches for the keyword , selected by the user in the text of the files stored on the network.
It is a system of searching in the complete text, not just on the menus or in the names of files.
WAIS uses Natural Query Language
The query is put into the system in natural language and WAIS discounts the irrelevant words and starts to search for the keywords

Searching For Documents With WAIS

You can gain access to WAIS in various ways:
Using a client program
Making a connection with quake.think.com and login as wais
Entering WAIS via WWW .

Domain Name Service && IP Address

Domain Name Service

Domain name is a way to identify and locate computers connected to the Internet.
No two organizations can have the same domain name.
A domain name always contains two or more components separated by periods, called dots(“.”)
Once a domain name has been established , ”Sub domains "can be created within the domain.

#The structure for this is:

Hostname.subdomain.second-leveldomain.top-leveldomain
DNS as a whole consists of a network of servers that map Internet domain names like www.google.co.in to a local IP addresses.
DNS enables domain names to stay constant while the underlying network topology and IP address change.
Each domain name corresponds to numeric IP addresses.
The Internet uses the numeric IP address to send data.

#For instance,

You may be connecting to a World Wide Web server with the domain name www.microsoft.com”, but as far as network is concerned, you are connecting to the web server with the IP address associated with that domain name.
E.g. IP address for www.microsoft.com is 192.11.1.1
Domain Name System completes the task of matching the domain names to IP addresses.
Domain names and their corresponding IP addresses, must be unique.
Domain Name System is a collection of databases that contain information about domain names and their corresponding IP addressing
Domain Name Servers are computers that translate domain names to IP addresses.
This system allows the Internet users to deal with the more sensitive domain names, rather than having to remember a series of numbers.
Domain name space is a hierarchical ,tree structured name space, starting at an unnamed root used for all DNS operations.
In DNS name space, each node and leaf in the domain name space tree represents a named domain.Each domain can have additional child domains.

#There are three components of DNS:

Resolver
Name server
Database of resource records(RRs)

Web Hosting || Virtual Private Network || Voice Over Network

WEB HOSTING

It is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via world wide web.
To put your web site on the Internet you need three things:

Domain name is an identification label that identify IP resources such as web sites.
E.g. www.google.com
Web host account is the account hosting companies
Web site is a site created by the user.

VIRTUAL PRIVATE NETWORK

It is a group of computer systems, connected to a private network.
It is secure way of connecting to a private LAN at a remote location using Internet.
VPN’s include encryption, strong authentication of remote users or hosts, and mechanisms for hiding or masking information about the private network topology from potential attackers on the public network.

VOICE OVER INTERNET

Internet telephony is the new technology, where phone calls can be made in any part of the world through the internet.
There are various web sites offering Net Telephony services like Net2phone, Vocal tec, net meeting.
Family of internet technologies, communications protocols and transmission technologies for delivery of voice communications and multimedia sessions over IP networks, such as Internet.

Listening the word Internet Concepts the first Question stuck to the mind is....

What is Internet..?

Internet is a global network of interconnected computers over world wide web.
It is a global web of computers that allows individuals to communicate with each other.
Internet consists of two types of computers:

Server
Server is a computer or program that fulfils the request of another computer or program.
Client
Client is a computer or program that requests a service of another computer or program.

Applications of Internet

Communicate with other people
Sharing information or resources
Connect to other computer systems

Types of Network

MILNET - Military Network
DARPA - Defense Advanced Research Network
BITNET - Because it’s Time Network
USENET - User Network
NSFNET - National Science Foundation Network.
ARPANET - Advanced Research Projects Agency/Administration Network

History of Internet

In 1969, the Department of Defense (DOD) of the United States (US) started a network using four computers at four separate universities throughout the United States enabling users to share resources and information, which was known as ARPAnet(Advanced Research Projects Administration Network).
In 1972, there were 37 computers connected to ARPANET. In that year, ARPA’s name was changed to DARPA (Defense ARPA).
In order to manage the size and complexity of the network were broken into two parts:
MILNET-for managing Military sites
ARPANET –for managing non-military sites(Network for research and educative purpose)
In 1970’s other networks like BITNET and USENET also come into being.
In 1980’s NSFNET was created. NSFNET allowed universities and research agencies to link up with its super computer.

# How Internet works...?

Internet is a global network of computers, each computer connected to the internet must have a unique address. That address is known as IP address.
Internet includes thousands of host computers(servers) which provides data and services as requested by client system.

Message starts
Message is divided into small chunks known as packets
Each packets are assigned a port number.
Each packets receives its destination address.
Data conversion from analog to digital and vice versa.
The ISPs router examines the destination address in each packet and determines where to send it.

ISP(Internet Service Provider)

When you connect your computer to the internet, you are connecting to a special type of server which is provided & operated by your ISP.
The job of this ISP is to provide the link between your browser & the rest of the internet.
The single ISP server handles the internet connections of many individual browsers.
The main component of providing access to the Internet consists of:
International connectivity, which allows you to connect to the amorphous(unstructured) Internet.
Domestic connectivity, which allows you to connect to the domestic gateway.
There are three ways an ISP can connect to the Internet:

VSNL(Videsh Sanchar Nigam Limited)/DOT(Department of Telecommunications)
STPI(Software Technology Park India)Private Operators
VSNL-VSNL is india’s leading provider of international telecommunications and Internet services.
DOT-DOT is responsible for issuing security clearances.

STPI- STPI is a semi government organization that has authorized to sell international gateway services to companies involved in developing software
Private Operators- Private operators are a private independent companies competing directly with the multi-system operators

Types Of Internet Connections

Connection Types

Dial-up Access
ISDN(Integrated Services Digital Network)
Leased Lines
Cable Internet

Dial-up Access

Also known as narrowband
Least expensive way to get connected with Internet
Speed is too low.
Use the Point-to-Point Protocol.
To use a Dial-up You need a modem.
Doesn't require any special H/W.
Only used for Email & light Web Browsing.

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