COMP10001 Lecture Notes - Lecture 9: Html, Meta Element, Hostname
25 May 2018
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Used to address machines
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Each device has a unique IP address
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Represented as 4 "8
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bit" integers, each in the range [0, 255]
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Statically
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an IP is reserved for a given device
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Dynamically
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an IP is allocated to a device when it connects to the Internet
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Allocated to a device
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IPs:
Used to address machines as well
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Made up of letters and full stops
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Structured hierarchically relative to a domain name and end with a top
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level domain
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Resolve to IP addresses via the Domain Name System (DNS) using name servers
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Hostnames:
21 = FTP
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25 = outgoing mail (SMTP)
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80 = HTTP
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110 = incoming mail (POP3)
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Machines communication via a collection of numbered ports
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Applications and Ports:
Internet resources are addressed via Uniform Resources Locators (URLs)
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Scheme = the protocol for accessing the file
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Hostname = the device the file lives on
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Port = access port (optional)
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Path = where the file lives on the device
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In the form scheme://hostname:port/path
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URLs:
Primary language used to mark
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up web documents is Hypertext Markup Language (HTML)
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Made up of elements which are used to mark
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up content
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Empty elements = backslash at end of tag
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Tag pairs = backslash at start of closing tag
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Tags are enclosed in angle brackets and take the form of
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Tags may contain attributes
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<i></i> = italics
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<b></b> = bold
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<u></u> = underline
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Basic textual tag pairs
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<!DOCTYPE html>
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<html>
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<head>
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</head>
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<body>
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</body>
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</html>
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Document structure
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Often contains a title (<title></title>
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Often contain meta
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data as attributes to empty meta elements
The head
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HTML:
Week 9
Saturday, 5 May 2018 5:27 PM
Foundations of Computing Page 1
