A browser is a computer program that allows a computer to display information from the Internet. It also provides a way for the user to access and navigate through this information space.
A browser can also be thought of as a client , sending requests to Web servers using Hypertext Transfer Protocol (HTTP) . Whenever a browser is started, or a user clicks on a hyperlink, or a Uniform Resource Locator (URL) is typed in, the browser sends a message to a web server (based on the address indicated by the URL) to have a file transferred. The browser interprets the information in the file so that it can be viewed in the browser window, or if necessary, through another program. The information displayed may be text or images. The browser interprets information written in Hypertext Markup Language (HTML) and displays this information in the browser window.
Files that have sounds or animation may require different programs to enable the information to be heard or seen. Most capabilities are built into the browser but sometimes the computer needs special equipment or programs. To hear sounds, for example, the computer needs a sound card, speakers, and software that enable the sounds to be heard. Some other files need a type of program called a plug-in in order to be viewed. For example, to read files written in Portable Document Format (PDF), users need to download the Adobe Acrobat program to their computers so the documents can be displayed in the browser window.
More than 100 different browsers exist, and most of them are available to download from the Internet for free; however, not all of them are usable on all computer platforms. There are specialized browsers, for example, that are designed to work only on devices such as personal digital assistants (PDAs) (e.g., Palm Pilots). Others only work on Macintosh computers, Windows operating systems, or UNIX computers.
The two most popular browsers are Netscape Navigator and Microsoft Internet Explorer. Both work on Macintosh and Windows platforms, in addition to others. Online services such as America Online and CompuServe have offered their own browsers for some time, but now most online services offer Netscape and Internet Explorer as well.
Most browsers share similar characteristics and elements, and employ many of the same options and techniques. In addition to providing ways for the user to navigate between web pages, browsers also generally allow a user to search for words in an individual web page. A browser also keeps a history of the web pages the user has already visited, and allows the user to organize what has been accessed. Users may save locations of web pages for easy future retrieval. Netscape's Bookmarks and Internet Explorer's Favorites organize URLs into files and save them indefinitely.
A browser allows the user to move between web pages by going back and forward, and features a scrolling device so that the user can move up and down a web page. Most browsers display the title of the current web page being viewed at the very top of the browser window. Browsers have menus with several elements available that can help the user manage the information found on the web. There are options such as saving a web page, sending a page, printing a page, and more. In addition, there are options that allow the user to copy text and other information from the current web page and paste it in other applications. Also included is the ability to search a web page for a word or phrase.
A web browser also provides a way for the user to view the HTML source of the current web page. This is a useful function for web page developers who want to know how a particular page was constructed and which HTML tags and elements were used in its design. The user may also view the vital information about a page, including the date the page was modified or updated, and whether it is a secure document for private transactions.
The option to reload a web page is also provided, as is the option to stop loading a page. Stopping is a useful option when a page is taking a long time to load.
History of Browsers
The browser as it is known today owes its development to Tim Berners-Lee, director of the World Wide Web Consortium (W3C) and a researcher at the Laboratory for Computer Science at the Massachusetts Institute of Technology. It was while working at CERN, the European Particle Physics Laboratory near Geneva, Switzerland, in the 1980s and early 1990s, that Berners-Lee developed the groundwork for the World Wide Web.
Crucial to the web's development was Berners-Lee's work in defining Hypertext Transfer Protocol (HTTP), a set of rules that enable a web page to be browsed using hypertext, and the language computers use to communicate with each other over the Internet. Hypertext, a term coined by Ted Nelson in 1965, and a concept invented by Vannevar Bush in 1945, is defined as a way of presenting information non-sequentially. It includes hyperlinks, or selections of text or images, that when activated by a point-and-click with a mouse, take the user to other related text or images. As the information linked to can include images and sounds as well as text, the term is more aptly named hypermedia.
Berners-Lee completed his work on the first World Wide Web browser in 1990 on a NeXT machine, a personal computer developed by Steve Jobs, founder of Apple Computer. Special features of the NeXT platform made it easier for him to try his idea of programming a hypertext client program on it, and combining it with the Internet.
While there were several hypertext projects being worked on in several countries at the time, none of the projects fit Berners-Lee's vision of what he wanted this system to look like, so he developed his own. He wrote the code for HTTP and invented the Universal Resource Identifier (URI), the scheme for document addresses. The most common type of URI is the URL. The browser he developed was called WorldWideWeb. He later renamed the browser Nexus so as not to confuse it with the World Wide Web itself. He also wrote Hypertext Markup Language (HTML) that contains the rules for formatting pages with hypertext links, or hyperlinks.
The problem with the WorldWideWeb browser was that it only ran on the NeXT computer. Browser clients were needed for use on PCs, Macintosh computers, and UNIX platforms. Universities in Europe and the United States were urged to take on browser creation projects. In 1992 students at Helsinki University developed a browser called Erwise that ran on a UNIX machine. At about the same time, Pei Wei, a student at the University of California, Berkeley, created Viola-WWW, a web browser for UNIX computers that was able to display HTML with graphics, load animations, and download small, embedded applications. Viola-WWW was a precursor to the popular software Hot Java, which was not in use until a few years later.
Mosaic, developed by Marc Andreessen and Eric Bina at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign, was the first widely distributed browser that was compatible with several platforms. It was also the first web browser with a graphical user interface (GUI) . It was released in 1993 as free, downloadable software on the Internet.
Mosaic introduced the Internet and the World Wide Web to a wide audience. The graphical interface made the web appear more exciting and made the information more accessible to people. Lynx, a text-only browser, was developed at the University of Kansas at around the same time. Lynx is still used by people who are not able to use graphical browsers due to their computers' limitations. It is also useful for users who want to view information only in text format, or those who are visually impaired and find that Lynx is ideal for use with Braille or screen reading software.
Many of the features of Mosaic were integrated into a new browser developed by Netscape Communications, a company formed with Andreessen and other people from the NCSA. In October 1994 Netscape released the first version of its browser, called Mozilla, as a beta, or test version. The commercial version, Netscape Navigator 1.0, was released in December of 1994 as a free, downloadable software package on the Internet. In August 1995 Microsoft released Windows 95 and the Internet Explorer browser. In the spring of 1998 Microsoft provided the Windows 98 operating system along with Internet Explorer 4.0, which came as an integral part of the operating system. Netscape Navigator and Microsoft Internet Explorer continue to compete with each other as the dominant software options in the web browser market.
The World Wide Web Consortium and other developers continue to try to create speech recognition software that will allow users to interact with the Internet using spoken words. People with visual impairments or those who access the web in situations where their eyes and hands are occupied, will find these browsers helpful. Also possible are browsers that talk back to the user. Other browser developments will include the full support of Extensible Markup Language (XML) and Resource Description Framework (RDF), both of which advance the organization of web information in a structured way. Browser programmers will continue to work on projects that increase the browser's capability to improve human-computer information processing in the complexity of the web environment.
see also Bandwidth; Internet; Internet: Applications; World Wide Web.
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Berners-Lee, Tim, with Mark Fischetti. Weaving the Web: The Original Design and Ultimate Destiny of the World Wide Web. New York: Harper Collins, 2000.
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Berners-Lee, Tim. "WorldWideWeb, The First Web Client." World Wide Web Consortium. <http://www.w3.org/People/Berners-Lee/WorldWideWeb.html>
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