Practical Guides for Beginners

6 Some basic terms

Here are the parts of a URL considered more closely.


Note: it's not essential to remember everything you'll find in this chapter. Just read it through so that you'll know where to find the information if it's needed.



In Chapter 3 'Web page and website' there appeared the following URL:


http://www.nypl.org/sitemap/index.html


Let's study more closely what the parts of this string indicate.



The parts of the URL:


http Protocol used in the communication between the browser and the web server.

'Protocol' is a set of rules a browser and a web server use to communicate with and understand each other.


: Colon simply separates the protocol from the other part of the web address.


// Indicates that a contact to a server is to be achieved. (For example, when sending email the notation 'mailto:<email address>...', without slashes, could be used). Note that this doesn't mean a connection between a browser and server. When a browser has sent a request, there is no connection between the browser and the server. (You can read more about how the web actually works here.)


www Name of a server listening to messages using the http protocol. Note that this name is not always shown in the URL in the Location Box. And the name can be something other than 'www'.


nypl.org Name of the domain where the web server belongs. Domain is like an address by which you can get to some specific 'area' on the Net. For example, the domain name 'nypl.org' is registered to The New York Public Library and there are probably several server programs in that domain each dedicated to different tasks.


www.nypl.org


This part of the URL is actually the name of the web server seen over the Internet. In other words, it's the server that hosts the web site of The New York Public Library. By using it the request a browser sends can be directed to the right web server.


You may wonder how a request can be directed to the right server if the name is not shown in the URL. In fact, the sequence is such that a request is first directed to the domain and then in the domain the right server is found. In the domain an http request goes to the server that is listening to messages using the http protocol.


/ Indicates the root folder of the folder system hosted by
the web server www.nypl.org.


sitemap/ Indicates a folder in the root folder.


index.htmlThe name of the document file requested.



Note that though there is a URL seen on the Location Box, the browser doesn't have a direct connection to a folder and a document file there on the disk of the server machine. It is always the web server that fetches the document and sends it to the browser. So nothing can be 'disturbed' on a web server by using a browser.



In folders hosted by a web server there is usually a file which is returned in case only the name of the folder is given. (For example, you can try what happens when you type 'nypl.org/sitemap/' on the Location Box and press Enter.) This specific default page can be named in several ways:

       index.htm

       Index.htm

       index.html

       Index.html

       default.html

       default.asp

       etc.


However, the name doesn't make a difference; a default page is shown if no other file is mentioned after the name of a folder.




You can study these things yourself by trying different URLs.




Summary


On some occasions this chapter may be helpful. For example, if you

have to give somebody a URL for a certain file, it's good to know

what a correct URL must contain.




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