ISP 523: Fundamentals of Information Technology

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ISP 523 Fundamentals of Information Technology

• Instructor Stephen Lackey
• September 7, 2005

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As We May Think

• http//www.theatlantic.com/doc/194507/bush/2
• What has changed since 1945 in terms of access to
  information technology?
• What has not changed? Are we better off today
  than we were in 1945?
• Have we created the world anticipated by the
  writer because of these advanced information
  technologies?

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Questions from last week

• What happens when you connect to a web server?
• What does the web server send to the browser?
• What does the browser do with it?

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What happens when you connect to a web server?

• Your browser contacts a web address (URL) to
  request a page
• http//albany.edu
• http is the protocol (a web page)
• Albany.edu is the network resource
• The network resource (albany.edu) finds/creates a
  file to send to your browser
• Your browser reads the file, parses it, and
  renders it accordingly.

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Whats a URL / URI?

• URI Universal Resource Identifier
• URL Uniform Resource Locator
• Absolute (whole address)
• Relative (address relative to current page)
• Fragmented (using bookmarks on page)

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What does the web server send to the browser?

• Depending on the request, the server must find
  the page or create the page using server-side
  programs or page fragments.
• The server may combine multiple sources of data
  to produce a single web page.
• The web server sends plain text documents using a
  Markup Language to indicate how to format and
  style the text of the page
• Its called HyperText Markup Language (HTML)

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Chapter 4 Web Server Basics

• The web was invented on the UNIX operating
  system, and is still primarily served from UNIX
  or a variation (i.e. Linux)
• Alternate web servers include
• Microsoft IIS / ASP
• PHP
• Apache (most common) files and CGI programs
• Coldfusion
• Many others

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Chapter 4 contd

• For basic content management, a web server may
  store pieces of web pages in various directories
  of the web server, and assemble them for each
  request.
• Inputs
• Static HTML files
• Server Side Includes (Ch. 18)
• Common Gateway Interface (CGI )
• Output
• HTML file

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What else you need to know

• How to set up your web account
• Where your web files are located on your
  Albany.edu UNIX account
• The URL for your web pages
• What is HTML?

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How to set up your web account

• Start your terminal emulator program (SSH)
• Connect to acunix.albany.edu
• Login with your net id and password (typically
  the same as your myAlbany or albany webmail
  account)
• Create default web directory
• Create public_html directory (mkdir public_html),
  set permissions for public read/execute
• - or type startweb and a UNIX batch program
  will do it for you.

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Where the web files are

• My net id SL239263
• My html files from UNIX /home1/s/s/sl239263/publi
  c_html/index.html
• The URL for the same page
• http//albany.edu/sl239263/index.html
• The contents of the /public_html/ directory are
  exposed to the web (if you set the correct
  permissions public read)
• If you create a subdirectory, your URL will be
  relative to your public_html directory.

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What is HTML?

• HyperText Markup Language
• A way to imbed structure into a flat text file
  using pairs of tags
• They can nest to arbitrary levels of detail
  tags are containers that can hold text or other
  pairs of tags.
• Tags are keywords surrounded by angle brackets,
  to form containers lthtmlgt some text lt/htmlgt

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HTML History

• HTML is derived from an older, more complex
  markup language, SGML
• Standard Generalized Markup Language
• Developed in 1990 by Tim Berners-Lee as a means
  for physics researchers to communicate their
  findings more quickly and efficiently
• Based on earlier research on hypertext linking
  of documents, allowing a non-linear means of
  accessing documents
• HTML is superceded by XHTML, an XML version of
  HTML

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Chapter 8 HTML Overview

• Basic structure of document
• ltHTMLgt
• ltHEADgtlt/HEADgt
• Contains document metadata (data about the
  document)
• ltBODYgtlt/BODYgt
• Contains document itself
• lt/HTMLgt

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The HTML container

• The HTML root contains two nodes (branches)
• ltheadgt
• ltbodygt
• These comprise the two basic structural elements
  of an HTML document
• Head meta information about document
• Body the (usually) readable content of document

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More about tags

• A tag is a container
• It is really made up of elements and attributes
• ltELEMENT ATTRIBUTEvaluegtsome textlt/ELEMENTgt
• Tags must be nested they cannot overlap
• ltbgtltIgt some textlt/Igtlt/bgt

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What do browsers ignore?

• Whitespace
• More than one space
• Tabs
• Linefeeds
• Comments lt! some ignored text ?

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Chapter 9 Structural Tags

• ltHEADgt
• ltTITLEgtMy First Web Pagelt/TITLEgt
• ltMETA/gt
• ltBASE/gt
• ltLINK/gt
• ltSCRIPT/gt
• ltSTYLE/gt
• lt/HEADgt

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Metadata for document HEAD

• HEAD container for
• META - Metadata about document (kewords,
  generator, etc)
• TITLE the text that appears on the title bar of
  the browser
• LINK relates to external files
• SCRIPT javascript code used in Dynamic HTML
  (ch. 28, 29)
• STYLE CSS stylesheet for document

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Looking Ahead

• Document formatting structuring content
• Headings (ch 10)
• Paragraphs
• Lists
• Anchors (links) ( ch. 11)
• Tables (ch 13)
• Document Styling
• Cascading Style Sheets (ch. 17)
• Fonts, colors, borders, other effects