Computer Network 

Compute Network

When you have two or more computers connected to each other, you have a network. The purpose of a network is to enable the sharing of files and information between multiple systems. The Internet could be described as a global network of networks. Computer networks can be connected through cables, such as Ethernet cables or phone lines, or wirelessly, using wireless networking cards that send and receive data through the air.

In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain sub networks.

The most common topology or general configurations of networks include the bus, star, token ring, and mesh topologies. Networks can also be characterized in terms of spatial distance as local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs).

Web Page

What a web page

A web page is the representation of a document which resides at a remote site. This is key to understanding what the web itself is and the implications. If a "web" document resides on the machine you are working from, the document is called an HTML document.

A web page has the wonderful feature of allowing embeded references to other pages.

Please, let me explain by example. The page you are reading right now resides in Alexandria Virginia, the USA. The author (thats me) edits the page from a dingy apartment 5 minutes north of the nations capitol. In fact, I work in DC at NASA HQ. Stop by if you are ever on capitol hill.

When you "visit" this web page you are instructing your browser to go get a copy of of this page from Virginia. The computer then uses the telephone wires to request a copy from the machine in Virginia. The machine in Virginia sends back the copy and viola, there it is on your screen. If the page were to be modified this evening and you came back tomorrow you would see the new web page (ignore caches for now).

So what?

So... in essence you are "looking over my shoulder". When I make a change here in DC you can see it as soon as you load the page. Because of this, web pages are often called "live documents". Wouldn't it be neat if documents (books, magazines etc..) with time sensitive material could update at any time? It *is* neat and its called a web page.

Implications

You should be excited right about now if this is the first time you are realizing this. Each web page puts you in contact with the author. So if you visit the Database of China Law and Taiwan Law (Li & Partners) page you are getting a page from a machine in Taiwan. That is what the "tw" means in the URL of the page (http://www.law.com.tw). The Law web page is maintained by folks who *live* in Taiwan. No middle man to interpret for you. No news anchor to tell you what Taiwan Law is.. hear it is from Taiwan itself.

And because of the availability of "cyberspace" virtually anyone can put up a page saying anything. A soap box to the world if you will. I certainly enjoy it. Send me mail .. let me know you stopped by.. I love to keep all the nice letters folks send me from all over the world. I may even add yours to this web page! Makes the world seem cozy and warm doesn't it?

Applications

* A weather page - updated every hour with current weather reports.

* Stock tickers - stock prices which are updated every 15 mintues.

* Store fronts - go to Amazon and buy a book from the largest book store I know of (2.5 million titles) without having to go to Washington state (USA). Oh and you don't have to browse if you don't want to. Just type in the name of the book you want on the Amazon page and they will tell you the price.

Web Browser

What is a Web Browser?

Browser, short for web browser, is a software application used to enable computers users to locate and access web pages. Browsers translates the basic HTML (Hypertext Mark Up Language) code that allows us to see images, text videos and listen to audios on websites, along with hyperlinks that let us travel to different web pages. The browser gets in contact with the web server and requests for information. The web server receives the information and displays it on the computer.

There are different browsers for various things you do on the internet. There's a text based browser. With a text based browser you are only allowed to see text. Graphical material are not displayed. Hyperlinks are accessed by typing it in through the keyboard. An example of a text based browser is LYNX. There's a graphical browser and that allows the user to see all types of multimedia.

There are several types of browsers but the one thing they have in common is that they carry out the same function; they transfer hypertext. Here are some familiar common web browsers:

* Mozilla FireFox

* Netscape Navigator

* Microsoft Internet Explorer

Every browser features a toolbar that allows you to perform various functions like:

* Go back to the first page you started on the internet which is called Home.

* Book your favorite websites

* Print content you find interesting on web pages

* Check your web history, like the websites you visited in the past

* You can go forward and backwards to see the previous sites you viewed

There are two basic ways that you can navigate through the browser:

* You can click on links on different web pages. Those links will lead you to other web pages.

* If you know the URL or the address of the website you can type it in write in the browser's box all the way at the top. There's no need to type in the: http:// part when inserting the address because the browser automatically places it in. Then you have to click enter.

Once you click enter you have to wait for the page to load. While it's loading you will see the browser icon. Usually a little box will appear at the bottom with bars. It's called a status bar. When all the bars are filled you will know that the page has finished loading.

So every time you click or a link or enter a URL your browser will request the information from the web server. If your browser returns to the page with a error message the address you typed in could be wrong on you may not be connected to the internet.

Web pages can look different in various types of browser. It's always important to download the latest version of your browser. Today most web pages are designed to be viewed in updated browsers. By keeping up with the most up-to-date version of your web browser you will be able to get the best of the web for everything that you need.

URL

Each day when we use the Internet to check our mail online, visit a web page or browse an FTP folder, we use our browser. And while there can be a great number of Internet browsers out there, each of them offering different functions and boasting a different design, one thing that unites all of them is the fact that they are built with a single purpose - to handle URLs.

The URL

Each file available on the World Wide Web can be identified and accessed through its corresponding URL. Standing for Uniform Resource Locator, a URL represents the global web address of documents, including web pages or image files, and programs such as CGI applications or Java applets. Its main mission is to identify the location of a document or a program available on the web and specify the mechanism for accessing it through a web browser.

The URL structure

A URL has a linear structure and is comprised of two main parts. It begins with a short protocol identifier, i.e. the name of the protocol that is to be used for reaching a particular document or program file. The most commonly used protocols are 'http' for viewing web pages, 'ftp' for transferring files over the Internet and 'mailto' for transmitting emails. The protocol name is followed by a resource name, which specifies the actual file address, including the domain name or the IP address where it is located and the exact pathname to that file.

While the protocol name is system pre-defined, short, and may contain only letters, the resource name could vary in length, depending on the specifications given by the user, and could contain letters, numbers and a hyphen. Both URL parts are visually separated by a colon and two forward slashes.

The URL in everyday life

Let's take a look at a few examples that will further clarify what stands behind a URL. For instance, if you look at the address bar of your browser you will see that the URL of the web page where this article is located is:

http://www.ntchosting.com/internet/url-global-web-address.html

Here you see the 'HTTP' protocol used for retrieving website files from the server where they are located with the help of a web browser. The resource name here is comprised of the domain name 'ntchosting.com' and the file pathname '/internet/url-global-web-address.html', where '/internet' and '/www' are hierarchically ordered folders, and 'url-global-web-address.html' is the name of the article file itself.

Search Engine

A program that searches documents for specified keywords and returns a list of the documents where the keywords were found. Although search engine is really a general class of programs, the term is often used to specifically describe systems like Google,  Alta Vista and Excite that enable users to search for documents on the World Wide Web and USENET newsgroups.

Typically, a search engine works by sending out a spider to fetch as many documents as possible. Another program, called an indexer, then reads these documents and creates an index based on the words contained in each document. Each search engine uses a proprietary algorithm to create its indices such that, ideally, only meaningful results are returned for each query.

On the Internet, a search engine is a coordinated set of programs that includes:

* A spider (also called a "crawler" or a "bot") that goes to every page or representative pages on every Web site that wants to be searchable and reads it, using hypertext links on each page to discover and read a site's other pages

* A program that creates a huge index (sometimes called a "catalog") from the pages that have been read

* A program that receives your search request, compares it to the entries in the index, and returns results to you

An alternative to using a search engine is to explore a structured directory of topics. Yahoo, which also lets you use its search engine, is the most widely-used directory on the Web. A number of Web portal sites offer both the search engine and directory approaches to finding information.

Different Search Engine Approaches

* Major search engines such as Google, Yahoo (which uses Google), AltaVista, and Lycos index the content of a large portion of the Web and provide results that can run for pages - and consequently overwhelm the user.

* Specialized content search engines are selective about what part of the Web is crawled and indexed. For example, TechTarget sites for products such as the AS/400 (http://www.search400.com) and CRM applications (http://www.searchCRM.com) selectively index only the best sites about these products and provide a shorter but more focused list of results.

* Ask Jeeves (http://www.ask.com) provides a general search of the Web but allows you to enter a search request in natural language, such as "What's the weather in Seattle today?"

* Special tools and some major Web sites such as Yahoo let you use a number of search engines at the same time and compile results for you in a single list.

* Individual Web sites, especially larger corporate sites, may use a search engine to index and retrieve