It all began at the high-energy physics laboratory in Geneva, Switzerland, named CERN. The simple problem encountered by the scientists involved the time delay in disseminating research papers and other documents. And this time delay wasn't restricted to the nucleus of buildings on the CERN campus; their vital statistics were shared throughout the world. It is Tim Berners-Lee, who is credited with designing the system that would allow scientists to easily share fairly complex materials using a simple set of protocols over the Internet (the term used to describe all the worldwide interconnected TCP/IP networks).
TCP/IPis an abbreviation for Transmission Control Protocol/Internet Protocol. A set of protocols that applications use for communicating across networks or over the Internet. These protocols specify how packets of data should be constructed, addressed, checked for errors, and so on.
Tim broke his solution down into two parts: HTTP, the Hyper Text Transfer Protocol definitionwhich provided a simple way for users to request and receive files over the Internetand the more familiar HTML or Hyper Text Mark-up Language. Unlike HTTP which defines how information is sent or received, HTML defines the visual presentation of the material on the receiving end.
Needless to say, as originally designed, HTML was never intended for the variety of display potentials presented by today's multitasking object-oriented operating systems like UNIX and Microsoft Windows. Nor was it ever designed to create wild multimedia sites that incorporated graphics and animation. The fledgling Internet was seen more as a library than as a virtual reality mall. As such, the original definition of HTML included as much output display control as would be needed by the typical scientific journal article.
Because HTML's protocols were succinct and complete, they were immediately accepted by the scientific community, which adopted it as their electronic typesetter. Scientists were particularly excited about HTML's ability to create links to other pages of information, making the documents much more alive than a static piece of paper. Unfortunately, this forward-only hot-link capability left something to be desired.
One of the earliest scripting languages was CGI or Common Gateway Interface. Its most common application is in forms processing. CGI allows you to create pages for users as individual requests come in, and you can customize pages to match that information.
The user usually fills out a form and clicks on a submit button. Then the user's browser sends a request to the server that includes information the user entered into the form. The server then sends this information on to another program for actual processing and responds with the appropriate output at the client or user end. Actually, depending on the kind of server your site resides on, you can write CGI programs in C++, PERL, and even AppleScript.
PERL is undoubtedly the most common language used for scripting CGI in UNIX environments with its combination of C syntax and the power of UNIX regular expressions. It is possible to write simple programs in PERL with a minimum of effort.
These languages provide HTML developers with additional programming horsepower that enables them to make browsers do new and different things. Not everything has to take place on the server end; now the client can take on more of the responsibility of processing.
Plug-Ins and ActiveX
Netscape is originally credited with developing the first plug-ins; Microsoft with developing ActiveX controls. The idea behind both is that the controlling software is loaded onto the user's computer (client), and then the Web page contains another file that contains the specific instructions or content.
While there are significant structural differences between plug-ins and ActiveX controls, their basic purpose on the page is basically the same. Like a Java applet, they add additional features and functionality to a Web page without directly affecting the host page. They also create a bidirectional communication between the end-user and the plug-in.
Java Applet versus Java ApplicationJava applets are programs that will only run when hosted by a Web browser, while Java applications are stand-alone programs that are designed to run on any system and need no Web browser or Internet connection.
The downside to both technologies is that they add to the download time of the Web page. In addition to the time it takes to download and install the actual plug-in or control, there's also the extra time to download the content files. In addition, neither technology really provides interaction with other elements on the page. There are some ActiveX controls that provide features like tool tips or pop-up menus, but, like plug-ins, these items are operated directly by the control with no ability to go beyond the feature itself.
It Allows Every Type of Computer World Access!
The Web is, most importantly, platform independent. This means that you can access the World Wide Web regardless of whether you're running on a low-end PC, an Apple Mac, an expensive Silicon Graphics workstation, a VAX cluster, or a multi-million dollar Cray super computer!
Web BrowsersThe Electronic SEARS Catalog
A Web browser, as mentioned earlier, is a program that you use to view pages on the World Wide Web, sometimes called web clients. A vast diversity of Web browsers are available for just about every type of architecture you can imagine, most importantly graphical-user-interface-based systems or GUI systems such as X11, Windows, and Mac platforms. There are even text-only browsers available for simple dial-up UNIX connections.
Full Color Shopping at Your Fingertips
One of the key features of Web browsers is their ability to display both text and graphics in full color on the same page, and all of this with a simple URL address, followed very often by nothing more than consecutive mouse clicks. If you are just jumping onto your Internet surfboard for the first time, you may not be aware that in its fledgling state the Internet was accessed by non-standard, confusing, command-line, text-only protocols. Of course, today's state-of-the-art rendition reacts to simple mouse clicks and is much more interesting with its new sound and streaming video capabilities. Even 3D virtual-reality simulations are possible with VRML (Virtual Reality Modeling Language).
VRMLYou can find a very interesting World Wide Web Virtual Library at http://www.w3.org, supported by individuals interested in promoting/sharing information on this extremely exciting outgrowth of HTML.
Info Info Everywhere
Of course, the very name, World Wide Web, indicates that the information you are downloading is potentially distributed throughout the entire globe. Since the information you are accessing occupies vast amounts of disk storage particularly when you include images, multimedia, and streaming video, there hasn't been a computer built to date that could house this bit explosion in one physical location.
Actually, this distributed diversity of data storage repositories is to your advantage. Were this information stored in a single location, imagine the chaos generated by a downed mainframe! The Web is so successful in providing so much information because that information is distributed globally across thousands of Web sites. And the best part about the interconnection is that if one leg of the information route is interrupted, for any reason, an alternate Web link takes over.
Provides Full Bidirectional Communication
An exciting aspect to Web interaction is its provisions for you to "talk back." Take, for example, a radio or television broadcast. This is one directional output.
The exciting news is that with today's evolution of HTML your document's display instructions are not limited to text only, but can now include graphical and auditory elements and can communicate back to the server.