A Basic Introduction to the
WWW and HTML
How the World Wide Web Works
What is the WWW ?
• It’s a service available through the Internet which
allows the transmission and rendering of
multimedia documents
• It uses a special protocol named HTTP (HyperText
Transfer Protocol)
• It uses a set of network addresses named URL
(Uniform Resource Locator)
What is a protocol ?
• It is a convention or language which allows the
communication between any two computers
through a network
• The main protocol used by Internet is TCP/IP
(Transfer Control Protocol/Internet Protocol)
• There are many other protocols running under
TCP/IP. Examples:
– SMTP: Simple Mail Transfer Protocol
– FTP: File Transfer Protocol
Address format for the WWW:
Uniform Resource Locator
• http://www.nlm.nih.gov/visible/sample.htm
Protocol
Host
Directory
File
WWW: Client and Server
Client
Computer which is
asking for an archive
on the net
Internet
I
Server
Computer which
sends the desired
archive
WWW: Client and Server
Client
Internet
I
Client software:
HTTP
Netscape, Internet Explorer
(browser)
Server
Server software:
WWW Server
WWW: Client and Server
Cliente
http://www.nih.nlm.gov/visible/sample.htm
Internet
I
Server
www.nlm.nih.gov
Finding
Connecting
Retrieving
HTTP
Client software:
Netscape, Internet Explorer
Server software:
WWW Server
WWW: Client and Server
Client
Http://www.nih.nlm.gov/visible/sample.htm
Internet
I
Confirmation
Transference
Closing
HTTP
Client software:
Netscape, Internet Explorer
Server
www.nlm.nih.gov
sample.htm
logo.gif
return.gif
Server software:
WWW Server
How the Client Works
Client
Http://www.nih.nlm.gov/visible/sample.htm
sample.htm
logo.gif
return.gif
Client software
browser
Rendering by the browser
<HTML>
<BODY BGCOLOR=#FFFFFF>
<IMG SRC=“logo.gif” ALIGN=left>
<H1>The Visible Human Project</H1>
<HR>
<IMG SRC=“return.gif” ALIGN=left>
National Library of Medicine
Script in HTML
What is Hypertext
<HTML>
<BODY BGCOLOR=#FFFFFF>
<IMG SRC=“logo.gif” ALIGN=left>
<H1>The Visible Human Project</H1>
<HR>
<IMG SRC=“return.gif” ALIGN=left>
National Library of Medicine
<P><A HREF=“imagem.htm”>Amostras</A>
<P><A HREF=“http://www.who.ch”>WHO</A>
amostra.htm
<HTML>
<BODY BGCOLOR=#FFFFFF>
<IMG SRC=“logo.gif” ALIGN=left>
<H1>Visible Human: Amostras</H1>
<BR>
Nesta página você poderá achar algumas
amostras de imagens geradas pelo Projeto
“Ser Humano Visível” em três dimensões.
imagem.htm
What is HTML ?
• It’s a language for the specification of documents
(mark-up language)
• It specifies for the browser what are the elements
of a page (text, images, etc.) and where and how
they should be rendered
• A text file .HTM contains embedded mark-up
commands and tags, enclosed by < and >
• The browser interprets these tags and commands
and renders the page
Elements of HTML
• Tags for document definition:
title, head, body, etc.
• Tags for text definition:
paragraphs, color, size, font, emphasis, etc.
• Tags for placing images
• Tags for defining hyperlinks
• Tags for defining tables, forms, frames, etc.