sarkinen.com > johan > Teaching > Programming

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The world wide web consists of three core components:

1. Web servers - information sources, holders of information created and uploaded to servers by users and applications creating contents 'on the fly', like by accessing a database.
2. Communication - transfer of information
3. Web browsers - the user interface to information, presents information to the user - You. Like here and now.

Web Server Development

Web Server:

• PHP / Perl / Python - for web server programming
  • Also CGI - common gateway interface
• SQL - for web web server database handling

Communication

The transfer of information between web browsers and web servers is typically done using two primary protocols:

1. HyperText Transfer Protocol (HTTP)
2. Hypertext Transfer Protocol Secure (HTTPS)

The difference is in the case of HTTP all communication is sent in clear text - and can be easily intercepted - and in the case of HTTPS, the data is encrypted. The latter should always be use for any sensitive information and why banks, other financial institutions, tax filing, account information for your utilities, phone services, etc should always use HTTPS.

HTTPS comes with overhead in terms of speed and costs of implementation and operations why not always used.

If you haven't already thought of it, what communication protocol used is the first part of an Uniform Resource Locator (URL) - a "web address".

• <protocol>://<server-address>/<local-specification-how-to-access-information-at-server>.
  Examples:
• http://sarkinen.com/johan/teaching/.
• https://securebank.com/accessingmysensitiveinformation.

Web Browser Development

I.e. not development of web browser applications but development for web browser.

• Web Browser:
  • HTML - for web page content
    • http://en.wikipedia.org/wiki/Html
  • CSS - for web page style
    • http://www.w3schools.com/css/css_intro.asp
    • http://www.w3.org/TR/CSS2/syndata.html
  • JavaScript - for web page functionality
• ASP
  • Google what is ASP
  • w3schools' ASP Introduction

• Google HTTP
• Google HTTPS
• http://en.wikipedia.org/wiki/Uniform_Resource_Locator

### started 2011-10-04