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GLOSSARY

UDP - USER DATAGRAM PROTOCOL
URL - UNIFORM RESOURCE LOCATOR
UNZIPPING


• UDP, User Datagram Protocol is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP). Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically, UDP doesn't provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. Network applications that want to save processing time because they have very small data units to exchange (and therefore very little message reassembling to do) may prefer UDP to TCP. The Trivial File Transfer Protocol (TFTP) uses UDP instead of TCP.
  In the Open Systems Interconnection (OSI) communication model, UDP, like TCP, is in layer 4, the Transport Layer.
  

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• URL, Uniform Resource Locator is the address of a file (resource) accessible on the Internet. The type of resource depends on the Internet application protocol. Using the World Wide Web's protocol, the Hypertext Transfer Protocol (HTTP) , the resource can be an HTML page (like the one you're reading), an image file, a program such as a common gateway interface application or Java applet, or any other file supported by HTTP. The URL contains the name of the protocol required to access the resource, a domain name that identifies a specific computer on the Internet, and a hierarchical description of a file location on the computer.
  On the Web (which uses the Hypertext Transfer Protocol), an example of a URL is:
                                             http://www.cnsny.net/personal
  

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• UNZIPPING is the act of extracting the files from a zipped single file or similar file archive. If the files in the package were also compressed (as they usually are), unzipping also uncompresses them.
  When you download programs from shareware or freeware companies on the Web, they almost always send you a zip file (the file name has a suffix of ".zip"). You can usually extract the files from a zipped file just by double-clicking on it since many archives include a "self-extracting" program. Several popular tools exist for zipping and unzipping: PKZIP in the DOS operating system, WinZip in Windows, and MacZip in Macintosh.
  

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