[TECH NOTES] Introduction to Web Development

  • The internet:
  • A connection of computer networks using the internet protocol (IP). 
  • What is Internet Protocol?

  • IP is a simple protocol for attempting to send data between two computers.
  • IP address consists of 4 numbers, each of 8 bits.
  • An example to IP address is: 192.168.1.5
  •  

    Transmission Control Protocol (TCP)

  • TCP adds both multiplexing and guaranteed message delivery on top of IP.
  •  

    What is Multiplexing?

  • Multiplexing allows programs to use the same IP address. This can be achieved by introducing ports.
  • Port: is a number given to each program or service.
  • Programs access network connections using both IP address and port number.
  •   

    UDP Protocol

  • UDP is another protocol used by some programs like games and streaming media programs.
  •  

    Domain Name System (DNS)

  • DNS is a set of servers that map written names into IP addresses.
  • Some operating systems maintain local cache file called hosts file.
  •  

    Organizations

  • W3C: World Wide Web Consortium, which develop web standards.
  • IETF: Internet Engineer Task Force, which develops internet standards.
  • ICANN: Internet Corporation for Assigned Names and Number, which decides top-level domain names.
  •  

    Web Server

  • Web server is a program running on a computer and listens for web page request on TCP port 80.
  • Some popular web server software are: Apache and IIS.
  •  

    Web Browser

  • Web browser is a software application that displays web pages.
  • Some popular web browser software are: Internet Explorer and Firefox.
  •  

    Hypertext Transport Protocol (HTTP)

  • It’s a set of commands understood by a web server and sent from a browser.
  • Some HTTP commands are:

    • GET filename: for downloading file.
    • POST filename: send a web form response.
    • PUT filename: to upload file.

  • Web servers may return a special “error code” number to the browser and possibly followed by an HTML document.
  • Some common error codes are:

    • 200: OK
    • 301-303: Page moved (permanently or temporarily).
    • 403: Forbidden to access this page.
    • 404: Page not found.
    • 500: Internal server error.

  •  

    Uniform Source Locator (URL)

  • URL is an identifier for the location of a document on a web site.
  • URL consists of:

  • After entering the URL into browser, the browser will:

    • Ask DNS for IP address corresponding to the host of the URL.
    • Connect to that IP on port 80.
    • Ask the server to GET index.html
    • Display the resulting page on the screen.

  • Anchors: it’s a parameter added to the URL that identifies a given section of a web page.
  • Port: it’s a parameter added to the URL that identifies another pot other than the default port 80.
  • Query string: It’s a set of parameters passed to a web program. For example, query is sent to search program to perform search and return results.
  •  

    Web Programming Technologies

  • Hypertext Markup Language (HTML): It’s a markup language used for writing web pages.
  • XHTML: A newer, more rigidly standardized specification of HTML.
  • Cascading Style Sheets (CSS): It supplies stylistic information to web pages.
  • Javascript: It allows interactive and programmable we pages.
  • Asynchronous Javascript and XML (AJAX): It allows fetching web pages in the background for enhanced web interaction.
  • PHP Hypertext Processing (PHP): It allows the web server to create pages dynamically.
  • Structured Query Language (SQL): Interaction with databases.
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