Glossary: U

This page contains glossary terms beginning with the letter U.
!-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Word or Term Description or Explanation
UART Universal Asynchronous Receiver/Transmitter - a component that manages the reception/transmission of serial data from/to the outside world - it converts it to parallel data suitable for use within the computer
ucb (University of California at Berkeley) - it refers to a variant of the POP3 email server that doesn't support command buffering - the suffix /ucb disables command buffering, so ANT's !InetSuite has to wait for the response of a single command before sending the next single command
when mail from "mail.surfaid.org" stopped working, ANT recommended changing to "mail.surfaid.org/ucb", whereupon the flood-gates opened
UDP User Datagram Protocol - an alternative to TCP, used in cases where reliability is considered unimportant, or where a connection-oriented dialogue is not required - each datagram is fired into the network as a single IP packet, and if it gets lost before reaching its destination, then tough luck
Unix the operating system used by most of the computers that provide services on the Internet - unlike a personal computer system like RISC OS, Unix is designed to provide access to many users at once and almost always comes with built-in TCP/IP and so it has become very popular as a network machine - the main thing to watch out for when connected to a computer running Unix is that it allows very long file names that are case sensitive, i.e. Fred, fred and FRED are different - the reason most Internet servers run one of the many varients of Unix is that the Internet Protocol Suite was developed in the academic community which also embraced Unix in the seventies - Unix was not only freeware, but also offered more features than anything else available - also, because it had its own system programming language ('C'), it was the ultimate 'mix-and-match' operating system and a programmer's paradise
Upload transfer files or messages from your computer to a distant computer
UPS Uninterruptable Power Supply - a device connected between the mains supply and the computer, which provides a short term supply in the event of a power failure - this gives you a few minutes to shut down your applications and save your data in an orderly fashion (well, a bit more orderly than phut and a black screen!)
URL Uniform Resource Locator - a universal addressing scheme for Internet resources - the idea was introduced at the same time as the World Wide Web, and most web browsers support it fully - the general format is: protocol://machine.site/directory/filename

For example:
http://www.acorn.co.uk/acorn/Home
ftp://ftp.acorn.co.uk/pub/documents/pricelist


the first example is a hypertext page fetched from Acorn's World Wide Web server using HTTP, and the second is a file fetched from Acorn's FTP server, using anonymous FTP - other protocols supported include 'gopher:' and 'news:'
USB Universal Serial Bus - a bus-bar system developed by Intel and Microsoft to allow connection of up to 127 peripherals daisy-chained, internally or externally, giving a quick, simple, expansion potential for the computer - USB will allow 'hot' connection, i.e. without the need to power down the system while making the connection
Usenet the term used to refer to the Internet news network - Usenet is not a real physical network as such (although it was once, apparently) - it is a virtual network of news servers which communicate via the Internet - there is no central Usenet site - instead, news propagates around the world as each server connects to its news feed (another news server) and exchanges new articles with it - hence, no single server ever holds the entire contents of any given newsgroup
User-id UID - a name or number used to identify a specific individual user when accessing a remote system - often has to be followed by a password
User name on most host systems, the first time you connect you are asked to supply a one-word user name - this can be any combination of letters and numbers - it is a unique identifier that is linked to a UID in the Unix operating system(s) - this is done so that people don't have to go around and remember their UID
User port an 8-bit parallel interface which can be used for the input and/or output of data - commonly used for connecting to concept keyboards and for doing control experiments
UUCP Unix to Unix Copy Program - a protocol used on dialup connections to transfer files and execute commands - this can be used to let the server call the clients or vice versa and is extremely efficient on low bandwidth connections - this is the original protocol used to transport NetNews and also the original protocol on Usenet - there are actually two UUCP ports for the RISC OS: one is the port of Taylor UUCP and the other is the port of some other UUCP implementation
Uudecode a program that takes a uuencoded file (see next) and recreates the original binary file(s)
Uuencode a coding system by which binary data can be transmitted over a text-only email system - Uuencode takes data using bytes in the range [0-255] and encodes it to a limited range of ASCII codes, usually in the range [32-127] - as a result, the encoded data can take up more space than the original binary file

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