| 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. 158.152.18.44 = risc.demon.co.uk |
| 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
http://www.youmustbejoking.demon.co.uk/progs.apps.html 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 |