Web Pages are created with HTML
HTML files or web pages are plain
text (ASCII) tiles with a lot of tags. These tags are the
building blocks of HTML. The tags help document and displaying visual features
such as font size, color, italics etc. The tags are also used in creating
hyperlinks and embedding images, sounds, video
and other multimedia content. HTML tags come in pairs (most
of the times); there is a starting and a closing tag. Tag names and tag
attributes are enclosed in < /> signs.
Let us look at a simple tag - The Bold
tag that displays text in bold.
The
starting bold tag is <B> and the ending tag is </B>. Any text
enclosed between these is rendered
(displayed) in bold by the browser. Remember all closing tags have the extra
slash
(/).
Web Browsers
Though
the World Wide Web is a part of the Internet, it serves as an important interface through which all of the net can be
accessed. This interface to the Internet is the browser. The browser displays
the HTML files using the instructions in the tags. In addition, the browser can also display images and video.
The web has grown tremendously
over the few years and provides a vast range of experiences
including video, multimedia presentations, real-time collaboration, interactive
pages, radio and television broadcasts. With the use of
programming languages such as JavaScript. VBScript, Per!, PHP,
ASP, Java. VRML, the functionality of the web is being increased.
The pages on the web can also be linked to databases to provide dynamic content
to the visitor. This feature attests the active and
energetic nature of the web.
Data transfer over the web and
client-server interaction
Data transfer over the Internet starts
with an event.
The event
can be of human origin, for example, you start the browser (a client program)
on your computer and request for some information, say an HTML file, located on
a remote computer. There are two important
ways in which information is requested from a browser, a hyperlink is clicked or a URL is entered in the
"Address" or "Location" field.
The event can also be
generated from the instructions in a program. Thus, we can automate
uploading and downloading of files (data transfer) with the help of a program.
Let us
suppose you have requested for an HTML document from a remote computer using a web browser. The browser searches for the
remote computer and on locating it, passes the request to a program called the
server running on this distant computer. The server then checks up your request and tries to locate the HTML
file on its hard disk. On finding it, the server sends this file to your computer. If this HTML document has
embedded image, video, and/or sound
files, the information and the content of such files are also passed to the browser.
On receiving data from the server, the client
which is a browser in our case, starts to display the HTML page. The client holds the sole
prerogative on document display, with no involvement from the servers' side. Once it sends the
data to the remote computer, the server, so to say, washes its hands off it. On
receipt of all requested data, the client-server connection is lost. Thus, the next time this client asks for some
information from the server, the server will treat it as a new request without any recollection of
previous requests. This means that client-server
interaction is "stateless" with every new request generating a new
response. Email - How does it work? Email
client and programs
Email is the most used application on the Internet. Emails
allow users to communicate with each other almost instantly.
Daily millions of emails are sent from one part of the globe to the
other. You can receive and send emails from all systems whether it is a Windows
PC or a Unix machine (even my cell phone allows me to send
one!). Employing MIME, you can send video, pictures or sounds along with text
messages via email.
Each email account has a unique address. A general format for
an email address is:
Each email message consists of a header and
a body. The email header has the following information:
·
Recipient email address
·
Senders email address
·
Email address of the people to
whom a carbon copy (Cc) and blind carbon copy (Bcc) is been sent.
·
The subject line
The main email message resides in the
email body.
Emails can be sent by typing the
recipients' email address in the 'Send to' field. Any additional recipients can be specified using the Cc or
the Bcc.
File Transfer Protocol - FTP
The File Transfer Protocol is an
excellent method to transfer (download and send) files from
one computer to the other over the Internet. Though you can transfer files
using email, it is not a
good choice especially when the file size is large
or when you need to transfer several files. The
objectives of FTP are to:
·
promote file
(programs or data) sharing
·
efficiently
transfer data from one computer to another
·
provide a common platform for file storages among different
hosts
HyperText
Markup Language (HTM,L) basics and the format
of HTML tag
. The word HyperText
means that some text in the HTML document carries a link
to a different location. which can be on the same page or
another page. On clicking this 'hot spot' the viewer is transferred to that
location. The word Markup means that specific portions of a document are
marked up to indicate how they should be displayed in the browser.
The main purpose of HTML is to
describe the structure of a document and this structure
can consist of tables, lists, links, blocks of text such as paragraphs etc.
However, the formatting of HTML document, or how the HTML
document should look like, depends solely on the
browser. It is common knowledge that even different versions of the same
browser do not display HTML alike. Thus, HTML was not designed
for document layout - it simply describes the structure of the
document. So over the years, web developers have been employing
several tricks to layout web pages.
Cascading
Style Sheets are now supported pretty well by all modern browsers though there are still some differences to be ironed out.
An HTML
document is a plain ASCII text file and, typically consists of a HEAD and a BODY. The head encloses style attributes, meta
tags and any client side scripting while the text for the document along with formatting rules are placed in the body
section.
Each
HTML document begins with the <HTML> tag and ends with </HTML> tag.
The head is enclosed in <HEAD>
and </HEAD>. Similarly all the elements inside the HTML body
section are encased in <BODY> and.</BODY>.
There
are hundreds of HTML tags and some of
these are proprietary, which means that only some browsers recognize them. HTML tags come in a pair - there is a starting and
an ending tag... though there are some exceptions
to this rule.
An HTML
tag is easily recognized because it is enclosed between < and > signs. The
format of a tag is as follows:
<TAG-NAME
[ATTRIBUTE1= [value1]] [ATTRIBUTE2= [value2]]...> Some text
</TAG-NAME>
As you will
notice, the ending tag differs from the starting tag by a slash (/).
Also,
most HTML tags also have attributes associated with them. These
attributes change the properties of
the tag. Most of the attributes also need a value through which formatting is achieved. A tag can have many attributes. These
attributes are placed inside < and > signs of the starting tag. Tags can also be nested to
increase the formatting feature of the text enclosed. Finally, inclusion of
multimedia content such as images, animation, sound clips, video etc. on HTML pages is achieved by using tags.
No comments:
Post a Comment