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Lesson 3Internet addresses
ObjectiveIdentify Components and Function of URL

Identify Components and Function of URL

How do you address a message so that it reaches the appropriate destination? Traffic on the Internet reaches the correct destination through the use of name and address conventions. The "address" of a Web resource consists of the domain (for example, plus additional information regarding the resource on the Web server (for example, The full "address" is called a Uniform Resource Locator, or "URL."
For example,
  1. is a URL, while
  2. is a domain name.

A URL specifies a unique address to a resource on the Internet. A resource can be a specific
  1. web page,
  2. a document, or
  3. an image.
URLs are sometimes called URIs, or Uniform Resource Identifiers[1], but URL is the more common term.

Parts of a URL

Delimiters separate the parts of a URL address. In general, the first part of a URL indicates which protocol to use; the second part specifies where the resource is located. The following diagram identifies and defines each part of a URL:
URL consisting of 1) https 2) Delimeter, 3) domain name 4) directory 5) Name of file

https Service or protocol. Type of Internet service the browser uses to access the resource.
//. Delimiter
www Optional host name for Web resources on HTTP servers. The domain name. This will take you to the home page of the site.
/website-deployment/ directory - location of the resource on the host server
/url-functional-components.php/ The filename of the specific web page document.

Key Web Technologies: URLS, HTTP, and HTML

The key elements for the development of the internet include an internet protocol to specify
  1. the client-server interaction,
  2. a way to identify the location of a resource, and
  3. a way to create content not dependent on a proprietary format, which was the HTML format.

These technologies of the web are explored further at the following course. Internet Protocols. Initially, Berners-Lee (1999) proposed a URI, a Uniform Resource Identifier (URI), as the way to identify a resource, but the IETF standards body changed this to the now familiar URL, the Uniform Resource Locator. URLs have a standard syntax. They begin with a protocol followed by a colon and a double forward slash, followed by a Fully Qualified Domain Name (FQDN, i.e., a host at some domain), followed by the directory path to a resource ending with the full file name. Figure 3.3 shows the structure of a sample standard URL. Besides the usual HTTP that start the standard URL, they can also accommodate the other Internet protocols that were prevalent at the time of its development, for instance a URL could designate "gopher" or "TN3270" as the protocol in place of the HTTP. So in addition to
http://hostname, "tn3270:// hostname" or "gopher://hostname" could be valid URLs as well. 

The format of a standard URL
Figure 3.3: The format of a standard URL.

Filenames are not always required elements to end a URL because several default names are sought by a server when the path ends with a machine or directory name. For example, the HTML files 1)welcome.html or 2) index.html is sought by the server without being specified in the URL. URLs frequently point to resources on Web servers running on UNIX machines, making case sensitivity a potential issue. However, most browsers have a "smart browsing" feature to overcome this problem. Long URLs can be shortened with the creation of an alias name and a subsequent HTTP redirect. Alternatively, services such as can be employed to provide shortened URL aliases and redirects. However, when URLs appear in HTML the match must be exact.

Other Uses for URLs

Uniform Resource Locators (URLs) are used widely across the internet and digital communication to perform a variety of functions. Here are some typical uses for URLs:
  1. Web Navigation:URLs are most commonly used to navigate to web pages. They provide the address for a specific resource on the internet, allowing users to access a variety of digital content including websites, blogs, news articles, and more.
  2. Linking:URLs are used to create hyperlinks in digital content, enabling users to click on a link and be directed to a different page or site. This is a fundamental feature of the web, allowing for easy access to related information and resources.
  3. File Download:URLs can be used to directly access and download files from the internet, such as documents, images, software, and media files. By entering the URL into a web browser or a download manager, the specified file can be retrieved and saved locally.
  4. Media Streaming:URLs are used to stream video and audio content over the internet. Services like video hosting platforms, music streaming apps, and live broadcasting use URLs to deliver media content to users in real-time.
  5. API Access:In the context of web development and software integration, URLs serve as endpoints for API (Application Programming Interface) services. They allow applications to communicate with each other and exchange data over the web, enabling functionalities like social media integration, online payments, and data retrieval from external sources.
  6. Email Links:URLs are often embedded in emails to provide direct links to web pages, promotional content, or to facilitate actions like email verification, password resets, and account management.
  7. Social Media Sharing:URLs are essential for sharing content on social media platforms. Whether it's sharing a news article on Facebook, a video on Twitter, or a product page on Instagram, URLs make it easy to distribute content across different networks.
  8. Bookmarking:URLs are used to bookmark web pages for easy access later. Most web browsers provide a bookmarking feature that saves the URLs of preferred pages, allowing users to quickly return to them without having to remember the exact address.
  9. Search Engine Indexing:URLs are crucial for search engines to index the vast array of content available on the internet. They provide unique identifiers for individual pages, helping search engines organize and retrieve content in response to user queries.
  10. Online Advertising:In digital marketing and online advertising, URLs are used to direct users to promotional content or landing pages. They play a key role in tracking the effectiveness of advertising campaigns and understanding user behavior.

These uses highlight the versatility and fundamental importance of URLs in facilitating access to information, services, and functionalities across the internet.
In the next lesson, the specifics of domain names will be discussed.
[1]Uniform Resource Identifiers: A Uniform Resource Identifier (URI) is a unique string of characters that identifies a specific resource, either physical or abstract. This can include resources like web pages, email addresses, phone numbers, books, and even real-world objects like people and places. Think of it as a unique "label" for anything that can be referenced or accessed.

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