Montecino's CS 103 Course Page

Lecture 4
 The Internet, html and Unix

The Internet - A global network of thousands of computer networks linked by data lines and wireless systems. 

Background history on the Internet -The Internet, originally the ARPAnet (Advanced Research Projects Agency network), began as a military computer network in 1969. Other government agencies and universities created internal networks based on the ARPAnet model. The catalyst for the Internet today was provided by the National Science Foundation (NSF). Rather than have a physical communications connection from each institution to a supercomputing center, the NSF began a "chain" of connections in which institutions would be connected to their "neighbor" computing centers, which all tied into central supercomputing centers. This beginning expanded to a global network of computer networks, which allows computers all over the world to communicate with one another and share information stored at various computer "servers," either on a local computer or a computer located anywhere in the world. The Internet is not governed by any official body, but there are organizations which work to make the Internet more accessible and useful.]

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 World Wide Web (WWW) - A hypermedia information storage system which links computer-based resources around the world. Computer programs called Browsers enable words or icons called hyperlinks to display, text, video, graphics and sound on a computer screen. The source of the material is at a different location - a different file in the same directory, a file in another computer, which can be located anywhere in the world.

The WWW was invented in 1990 by a CERN - (European Laboratory for Particle Physics - ( computer scientist. It was originally conceived and developed for physics collaborations, which require for instantaneous information sharing between scientists working at different universities and institutes all over the world. This software used URLs, HTTP and HTML.

Marc Andreesen was instrumental in creating the first public WWW browser, Mosaic, in 1993, through the University of Illinois National Center for Supercomputing Applications (NCSA).  Mosaic was initially developed for UNIX, then adapted to Windows applications.

URL - A universal resource locator (a computer address) that identifies the location and type of resource on the Web. A URL generally starts with "http."

Domain Name - URL addresses can be recognized by the "Domain Name." Domain Names are divided into categories such as: 
.edu - for education sites
.gov - for government sites
.org - for organization sites
.com - for commercial sites 
.net - for network infrastructures

UNIX - The operating system which we use to create our Web pages and use Pine email. It is a multiuser, multitasking operating system, with many versions, that is widely used  in workstations and servers. UNIX is written in C, and both UNIX and C were developed by AT&T and freely distributed to government and academic institutions. Here are some examples of basic UNIX commands.

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The Internet is not the only WWW application.

A few other applications using the Internet:

FTP ( file transfer protocol) - software to receive from upload) or send to (download) files (text, pictures, spreadsheets, etc.) from one computer/server to another.

Telnet - a program that you can use to log in to another computer ("host") on the Internet and then use its functions. Some web browsers use Telnet as a "helper application" to connect to a remote machine.

Example: telnet://

Pine ® - software for Internet News & Email - tool for reading, sending, and managing electronic messages using a non-graphical interface - without getting on the WWW (the Web).


HTML - A type of text code (tags) in Hypertext Markup Language which, when embedded in a document, allows that document to be read and distributed across the Internet. See examples of html tags

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See Guidelines for Student Web pages - protections and precautions

SeeCopyright and the Internet

Client/server - The client- requesting maching (personal computer or workstation) - is computer which receives applications / information / data / access to the Internet , etc., for the  individual computer users. The server is the "master" computer which sends/ supplies the applications / information / data / access to the Internet to the individual computer users. A local area network (LAN) or wide area network (WAN) connects the server to a number of client computers , run by individual users.

IP ADDRESS - The number or name of the computer from which you send and receive information on the Internet. The address of a computer attached to a TCP/IP network. Every client and server station must have a unique IP address. Client workstations have either a permanent address or one that is dynamically assigned to them each dial-up session. IP addresses are written as four sets of numbers separated by periods. For example -, The IP address can also be a name, such as, which corresponds to a number.

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TCP/IP - (Transmission Control Protocol/Internet Protocol) A communications protocol developed under contract from the U.S. Department of Defense. This UNIX standard has become the standard protocol of the Internet and the global standard for communications.

TCP - provides transport functions, which makes sure that the total amount of bytes sent is received correctly at the other end. 

IP - provides the routing mechanism. TCP/IP is a routable protocol, which means that all messages contain not only the address of the destination station, but the address of a destination network. This allows TCP/IP messages to be sent to multiple networks within an organization or around the world.

Every client and server in a TCP/IP network requires an IP address, which is either permanently assigned or dynamically assigned at startup.

ISP - Internet Service Provider - Small providers typically provide service via modems and ISDN while the larger ones also offer private line hookups, such as T1 lines.

T1 line - A 1.544 Mbps point-to-point digital line provided by the telephone companies, and used for private networks and high-speed links to and from Internet service providers. The first T1 line was introduced by AT&T in January 1983.

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ISDN - (Integrated Services Digital Network) An international telecommunications standard for transmitting voice, video and data over digital lines.

PPP -(Point-to-Point Protocol) A data link protocol that provides dial-up access over serial lines (SLIP).

SLIP - (Serial Line IP) A data link protocol for dial-up access to TCP/IP networks. It is used to gain access to the Internet and provide dial-up access between two LANs.

Netiquette - acceptable standards of behavior on the Internet. 
Netiquette Web Sites: &

Disinformation -  The WWW, because of the inexpensive and sometimes "free," democratic nature of the Web, anyone can post information, whether it is credible or not. See these guidelines for critiquing Web sites.  Also be wary of email message hoaxes - for ex: messages about needy people needing money, help;  computer virus scares.  Some messages of this nature may be valid, but more often than not, someone is playing a joke at your expense.  E-mail "chain letters" violate the GMU computing policy. Don't be victims of Internet scams.

Search Engines - See Searching the WWW. See explanation of how different search engines work and explanation of Boolean logic.

Newsgroup - An Internet "site" centered around a specific topic. Some newsreader software can "thread" discussion so there can be various topics centered around a central theme. An advantage over e-mail is that the messages are archived and don't reside in your e-mail account, taking up your memory, unless you set up a "sent mail" or "carbon copy" option. The messages can often be threaded according to a particular discussion.

Chat - A virtual room (communications channel) where a "chat" session takes place.  the word "room" is really a metaphor, not a real room.
Try out our CS 103 Chat Room. When the Chat room appears, scoll down until you see the message window and type in your message.  The messages of the other participants will appear in the top window.  The messages will disappear when you log off Netscape.  You and other participants have to arrange to go on the Web at the same time, but from anywhere you have access to a computer hooked up to the Internet. This is called synchronous communication.

bandwidth - The transmission capacity of an electronic line such as a communications network. It is expressed in bits per second, bytes per second or in Hertz (cycles per second). When expressed in Hertz, the frequency may be a greater number than the actual bits per second, because the bandwidth is the difference between the lowest and highest frequencies transmitted.

fiber optics - Fiber optic cable (made of glass or plastic threads) is a popular technology for LANs because of the greater bandwidth, which can transmit more information at the same time than metal cable. Some telephone companies are replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics. Data can be transmitted in a digital format (the natural form for computer data) rather than in an analog format. Fiber optics is more expensive and more fragile.

digital versus analog - Analog transmission goes from one value to the next in a continuous flow. Digital transmission occurs with discrete intervals. For example, when you turn the volume up on an analog radio the sound goes higher in a continuous movement. The same action with a digital radion causes the sound to rise in steps. Sometimes it is hard to set the volume at your comfort level - it is sometimes still too low or a bit too high. For a diagram, see the definition of "analog" at Webopedia:

Baud - The signalling rate of a line, which is the number of transitions (voltage or frequency changes) that are made per second. The term has often been erroneously used to specify bits per second. However, only at very low speeds is baud equal to bps. For example, 300 baud is the same as 300 bps. Beyond that, one baud can be made to represent more than one bit. For example, a V.22bis modem generates 1200 bps at 600 baud. Modems now transmit data at 56 bps, if the line is capable of transmitting at that rate and if the sending and receiving computers both have that rate and if the traffic does not slow things down.

cookie - Data created by a Web server that is stored on a user's computer. It provides a way for the Web site to keep track of a user's patterns and preferences and, with the cooperation of the Web browser, to store them on the user's own hard disk. The cookies contain a range of URLs (addresses) for which they are valid. When the browser encounters those URLs again, it sends those specific cookies to the Web server. For example, if a user's ID were stored as a cookie, it would save that person from typing in the same information all over again when accessing that service for the second and subsequent time. You can have your browser warn you before accepting a cookie. 

Modem - A device that connects your computer to the Internet, when you are not connected via a LAN (local area network, such as at work or on a campus.) Most people connect to a modem when using a home computer. The modem translates computer signals to analog signals which are sent via phone lines. The telephone "speaks" to the computer/server which provides your Internet access.

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Montecino's CS 103 Course Page