This chapter discusses various storage methods. The objectives important to this chapter are:
In the interest of time, I am cutting this chapter to the essentials.
Any networks can be connected to together to make a network that can be called an internet. When the word is capitalized, the Internet refers the global publicly accessible network that was created by the the United States Department of Defense. The Internet grows daily. It is not possible to measure it exactly because it is always changing, and because it is not under a central control any longer. It is a connection method between many separate networks.
One of the strengths of the Internet is that it is connected like a mesh, which means that it is connected like a fishing net. There are many possible paths that could be used to send a signal from one machine to another machine on the Internet. In fact, messages, files, and other signals sent across the Internet are broken into pieces called packets. Each packet is sent independently from each of the others. Each packet may be sent along a different path, depending on what paths are available when the packets are sent. The packets are numbered so that the receiver can reassemble them into the original message.
Every device on the Internet uses a protocol (set of communication rules) called TCP/IP (Transmission Control Protocol / Internet Protocol). Actually, these are only two protocols in a larger suite of them, but the suite is known by that name. Devices using TCP/IP are assigned addresses, called IP addresses. Usually, the address looks like the example on page 7.6: 18.104.22.168, four numbers separated by periods. There are millions of these addresses, and it would be hard for human beings to remember them, so a domain name system is used. The above address, according to the text, is assigned to a particular server owned by Microsoft. A domain name has been assigned to it: www.microsoft.com. With either the name or the address, a computer on the Internet can contact that server and request files from it.
The server mentioned above is a server for the World Wide Web, a graphic oriented part of the Internet invented in 1991. The terminology in the book is a little vague. A web page is a document that can be accessed on the World Wide Web. A collection of pages that are administered by a particular person are a web site.
Web pages work because of hypertext, which is a way of linking pages together. When you clicked on the link for this page that appears on the menu for this course, you were clicking on a hypertext link which told your browser how to get to this page. Web pages are written in a language called HTML (Hypertext Markup Language).
Anyone reading this page should know what a browser is, but that's the next topic. A browser is an application that is used to read and interact with hypertext pages.
One way to use a browser is to tell it to open a page directly. Servers and clients on the Internet have specific IP addresses and may have domain names. Pages do not. You access a specific page by using a URL (Uniform Resource Locator), which is often a domain name followed by a path (subdirectories) to a specific file name.
Another way to use a browser is simply to follow links to other pages, or to use a search engine to find a page. A search engine is a program that looks up web pages it knows about which match a description that you supply to it. Many good search engines exist, such as the ones listed on page 7.17, and they are all useful for finding information. Despite the impression some people have about the web, a search engine will not lead you to all pages. Most search engines only lead you to pages that the author of those pages has listed or registered with the search engine itself.
Some pages are available only to people within a certain network. These are intranets, web networks that are only for the use of specific individuals, such as employees of a company. An intranet may be protected by a firewall, a computer or a program that keeps others out. A firewall may be set up several ways, such as only granting access to users with specific IP addresses, or asking for a user name and a password before allowing access.
Connecting to the Internet is discussed on page 7.28. Several methods exist: