Glossary: R

This page contains glossary terms beginning with the letter R.
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Word or Term Description or Explanation
Radio icons a group of buttons within a dialogue box, only one of which can be selected at a time
RAID stands for "Redundant Array of Inexpensive Discs" - it is a method of speeding up server response and maintaining data security - you get a socking great array of discs that you can access fast in parallel, and part of the array is redundant so that if one of the discs falls over, you can recover the data from the other discs
with RAID 1 the data is 'striped' across the discs, i.e. any file that is large enough is split into parts, each being stored on a different disc - since reading and writing to discs is a potential bottleneck in any system, if all disc accesses happen simultaneously, the overall response time of the discs is greatly improved - there is the side effect that if an individual disc dies, all the files that were part stored on it are lost and this is a potentially larger disaster than if each disc held data in the normal form
RAID 2 uses mirroring between discs which means that a duplicate of one disc's contents are held on another - this ensures data security in that if one disc dies, the data is still stored - however, as each write operation must occur twice, the overall speed of the discs is slowed
RAID 5 is known as 'striping with parity' - this method gives an improvement in system response as well as greater data security - in effect, you only write data to two out of three discs, and write some function of that data onto the third disc for error-checking - at its simplest, this would mean writing one byte (or word, or whatever) to one disc, the next to the second, and the exclusive-OR of them to the third - when you read, you read back all three bytes at once, and you can do the exclusive-OR again to check that nothing has been corrupted - furthermore, if one of the discs stops working entirely, you can work out what was on it from whatever value is needed to get the right check (an exclusive-OR again, as it happens)
it is possible to implement RAID in software (Windoze NT Server does provide the options to implement either RAID 1 or 2), but for any sort of system speed and reliability (especially when using NT) a hardware solution is preferable
RAM Random Access Memory - this is the place within the computer where information is stored on a temporary basis - when the computer is switched off, information in RAM is lost
RAM disc part of the computer's RAM memory can be set aside so that the user can store files and data on a temporary basis during a computer session - the information is accessed through a filer in the same way that you would access an external storage medium such as a floppy or hard drive
RARP Reverse ARP - the protocol used to map a MAC address (like Ethernet) to an Internet address
RDP Remote Desktop Protocol (Networking)
Readme files files found on FTP sites that explain what is in a given FTP directory or which provide other useful information (such as how to use FTP)
Real Soon Now a vague term used to describe when something will actually happ
RealAudio a program for playing audio over the Internet
the system is implemented as a client/server architecture - the RealAudio server incorporates an encoder which compresses sound into Realaudio files - the client side is a web browser plug-in or add-on (Internet Explorer and Netscape Navigator have built-in support for RealAudio) which allows the stream of data sent from the server to be uncompressed and output using the normal sound facilities of the computer, such as a sound card
a 14.4k or better modem is required, and a 28.8k connection is recommended for music-quality sound
RealVideo a version of RealAudio which includes video pictures with the sound
Relocatable module a section of computer code that can be used to extend the facilities of the operating system and which can then be used by any application running in the computer
Remailer a computer server that automatically privatises email or Usenet posts by removing all identifying headers, thus making the sender anonymous
Remote login operating on a remote computer, using a protocol over a computer network, as though locally attached
Removable hard
disc drive (1)
this is a cross between a hard drive and a floppy drive - it uses a solid metal disc so that it can store large amounts of data (currently up to 270Mb on a single disc) but the disc is held in a plastic case like a thick floppy disc - the cartridge can be taken in and out of the drive so that a number of discs can be used for different purposes, and the data can be transferred easily from one computer to another
Removable hard
disc drive (2)
there is a second type of removable hard drive in which the whole drive mechanism is removed rather than just the cartridge
Reply to send a private email to someone, either in reponse to an email or to a news article
Resolution the complexity of detail that can be seen on a computer screen or a printer can be specified in terms of resolution, i.e. the numbers of dots per inch
Resolve translate a numeric IP address into a textual domain name, e.g. =
Resources the various programs and data files which an application uses to perform its task
RFC Request For Comment - aseries of documents that describe various technical aspects of the Internet
RGB Red Green Blue - any colour can be made up of a combination of different amounts of light of these three primary colours - so colour monitors (RGB monitors) use sets of three coloured phosphor dots of these three colours
RIP Raster Image Processor - this is a device used in the printing industry to produce a very high resolution output
RISC this is an acronym for Reduced Instruction Set Computer - companies like Acorn (and many years later, Apple, though not yet, apparently, Intel) realised that the trend to more and more complex computer processors wasn't necessarily the best way to increase the overall speed of computer processing - these complex processors were spending the majority of their time doing simple tasks anyway - Acorn made the processors simpler, which meant they could work much faster doing the simple jobs like pushing text around and drawing dots on the screen - this is partly why RISC processors are so well-suited to DTP applications (N.B. this explanation is a gross over-simplification which doesn't do justice to the brilliance of the designers of the Acorn RISC processors!)
RISC OS this is the operating system used on Acorn's RISC-based computers
RISC_OSLib a library supplied with Acorn's ANSI C compiler designed to help you program applications that run in the RISC OS desktop
RiscBSD one of two public domain Unix clones currently being converted from PCs to run on Acorn machines - the other is ARM Linux - RiscBSD is derived from FreeBSD and ARM Linux from Linux
RMA Relocatable Module Area - the area of RAM set aside for the program modules used by different applications
ROM Read-Only Memory - a form of non-volatile memory that remains unchanged even when the power is switched off and which cannot (usually) be altered (but see Flash ROM and EPROM)
Root directory the main directory of a storage device which contains all other directories and files and which is displayed when the iconbar icon of the device is clicked
ROT13 a method of trivially encrypting text so that it cannot be read accidentally - this is used to prevent the punchline of jokes being revealed before the user has read the joke, or for prventing users reading about the ending of books or films
Route the path (through gateways or servers) that mail or other information takes to get from source to destination
Router (1) software, usually invisible to the user, which automatically chooses the easiest pathways (on a network) for data to be transmitted
Router (2) a router is normally a computer or other dedicated hardware that is set up to transmit packets from one network to others - the difference between a router and a gateway is that a router will normally be connected to several networks, whereas a gateway is only connected to two networks - you can buy routers with additional functionality, including: dial-up/cable modem support for connecting to the internet; multiple network sockets (RJ45) so that it acts like a hub or swtch; one or more parallel ports so that it can act as a printer server; a firewall
ROX RISC OS on X - a project to develop a new windowing environment for Linux, combining the best of both RISC OS and existing Linux/Unix environments
RS232/RS423 these are two different (but similar) electrical standards for the transmission of serial data
RS485 this is a physical interface (layer 1 in the ISO protocol stack) for serial data transfer - it is usable as an asynchronous or a synchronous interface - it uses 5-volt levels and differential signalling, making it good for longish cable runs and is relatively immune to common-mode noise as compared to RS232 - it is usually implemented as a half-duplex arrangement, where all nodes listen and when one wishes to talk, its drivers grab the signalling lines and send out the data
RSS Really Simple Syndication or Rich Site Summaries is a way to alert the recipient of something new on a website, news stories for example - a single file is fetched containing titles, links to and brief descriptions of the full stories - the format used for this RSS file is XML based with HTML like tags - on RISC OS Ticker (PD) from displays the items on a scrolling window, clicking on one will go to the full story - alternatively, Hermes, from R-Comp (comes with DialUp and NetFetch), converts each item as an email with a link to the full story

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