Dictionary of computer jargon (M-R)

WA dictionary of computer jargon

Compiled by Jon Storm.
2022 edition.

You will certainly have noticed that there is lots and lots of strange gibberish associated with computers; and the industry just loves acronyms. Please bear with me for a moment while the table containing the definitions downloads.

The dictionary is divided into four sections, to speed up download and navigation :
this is M-R; click here for A-D (+ numbers); E-L; S-Z.

It says... It means...

Mac, Macintosh, Macbook The Apple Corporation's alternative to the PC, much loved by its devotees. It is the only widely available personal computer that doesn't use Microsoft Windows. Most popular Windows software is also released in Mac format. The Macbook is a laptop.

Mac address (Media Access Control) The unique serial number of an Ethernet card or other networking device. (Nothing to do with Apple Macs, despite the name). It is mostly used to identify which device is talking to which on a network, and is usually only needed when troubleshooting network problems. In the UK, a "MAC code" is a unique number used for switching broadband providers smoothly.

Macro A small program used to automate repetitive or complex tasks.

Mailbomb One or more very large emails, sent to someone maliciously to stop them being able to use their mailbox and/or internet connection, because all the available bandwidth is being used up downloading the mailbomb(s). See also DoS (Denial of Service).

Malware A catch-all term for software installed by stealth onto a PC for malevolent purposes (hence the name). These may include displaying unwanted ads (adware), installing software you didn't ask for, or spying on your activities (spyware) and reporting them back to the culprit so that he can steal your bank account, address book etc.

Mbps (MegaBits Per Second) A measure of speed of information flow over a network (and if it's measured in Mbps, it's reasonably quick.) A Megabit is one million bits. (Actually slightly more if you want to egt pedantic about it). See also bps, Kbps.

Megabyte Unit of measurement for pieces of information : approximately 1 million bytes or a thousand kilobytes. Often shortened to Meg or just M. See also Gigabyte, Kilobyte, Byte.

MegaHertz See MHz.

Megapixel A million pixels. Often used to measure the quality of digital cameras : the higher the number the better the camera.

Memory Also known as RAM. Where the computer holds whatever you are currently working on. The contents of memory are lost when the computer is switched off.

Meta The company which owns popular social media sites Facebook and Instagram.

MFD (Multi Function Device). A combined printer, scanner, photocopier and fax machine.

MHz (Megahertz). Millions of cycles per second. Most often used as a measurement of a PC processor chip's speed and power, with bigger numbers meaning more speed and a higher price. See also GHz.

Micro-filter A device which allows you to use an ordinary phone over a telephone line set up for an ADSL internet connection. Sometimes just called a filter.

Microsoft

The largest business software provider for desktop PCs and laptops, There best known software is Windows, now up to version 11, and Microsoft Office which includes Word, Excel, Access and Powerpoint, and Outlook, a combined mail and calendar program.

MIDI (Musical Instrument Digital Interface; pr. "middy") A very popular standard for controlling musical instruments connected to computers. A MIDI file is a list of instructions to play particular notes at particular intervals in particular styles, not a sound recording.

MLM (Multi-Level Marketing) A scam similar to pyramid selling, once much in evidence on the internet, particularly in spam. Despite the claims of those promoting MLM, it is of dubious legality in most jurisdictions.

MMORPG (Massively Multiplayer Online Role-Playing Game). An online role-playing game (RPG) designed to played by thousands of players simultaneously.

Modem (MOdulator/DEModulator) A device for allowing computers to communicate over a phone line, now largely obsolete.

Monitor The screen of a PC.

Motherboard The main circuitboard in the computer - all the other bits and pieces are plugged into it.

Mouse A device used to move a pointer around on the computer screen. Essential to get the most out of Windows, though it is not quite impossible to use Windows without one.

MP3 (MPeg-1 audio layer 3). A very popular standard for compressing audio and particularly music files down to a reasonable size with little or no perceptible loss of quality, and the files created using it - "an MP3" is an audio file. See MPEG, Compression.

MPEG (Motion Picture Experts Group; pr. "em-peg") A set of standards for compressing video and audio files, and the committee that came up with them. Also, often used to mean movie files created to the MPEG standard.

Nameserver An internet server which translates the alphabetic web addresses favoured by humans into the numeric ones used by computers.

Napster A pioneering peer-to-peer internet file-sharing system. Because much of the data shared was copyrighted, and thus being distributed illegally, the operators of Napster were hit with a number of large lawsuits by the music industry, and eventually closed down. The name was bought and is now used by a legal pay-to-download service.

Netbook A smaller version of the popular laptop computer format.

Network A way of linking several computers together so that their users can share resources such as printers and documents, often via a central computer called a server. See also LAN, WAN, Ethernet.

Network card, Network Interface Card An Expansion card which lets a PC communicate with a network, required for broadband Internet access. See also Ethernet, NIC.

Newbie (New beginner) Internet slang for someone who is new to using computers, the internet or a game.

Newsgroup (or just News) A public area where you can read and post messages on a particular topic or theme, allowing public discussion, either on the Internet or a Bulletin Board. Largely replaced by internet forums.

NIC (Network Interface Card) An Expansion card which lets a PC communicate with a network or use a broadband internet connection. Almost all modern NICs are Ethernet cards.

Noob Someone who is new to a game or internet service, derived from newbie

Notebook A portable PC, with system unit, screen and keyboard in one package. Also called a laptop.

OCR (Optical Character Recognition) A program which attempts to convert a scanned image (ie a picture) of text into text that can be edited in a word processor. The result is rarely 100% accurate and must be carefully proofread, but it can save a lot of retyping.

OEM (Original Equipment Manufacturer) A company that actually builds computers, as opposed to just retailing them. "OEM software" is ordinary software bought in bulk at a discount by the OEM and pre-installed on a new machines, usually without printed manuals. OEM software cannot legally be sold separately from a computer, so when offered for sale at huge discounts is either pirated, or not what it claims to be.

Office Suite A related group of programs for business use, usually including a word-processor, spreadsheet, database and a number of other programs. The best known is Microsoft Office.

Off-topic A message which is not relevant to a particular discussion, for example on social media. Posting off-topic messages annoys people and can make a discussion unreadable if there are a lot of them, so will often get the perpetrator banned.

Online Connected to the internet, or of the internet.

Open Source Software (usually) that is created and distributed with either relaxed or no copyright restrictions.

Operating System Every computer has an operating system, which is a sort of master program that runs automatically when you switch the computer on, and continues running till you switch off. It is responsible for the many routine tasks required to keep a computer running : moving the pointer when you move the mouse, providing icons and menus, running other programs such as a word processor or a game which you may request, controlling the various disk drives, the screen and so on. The most widely used PC operating system is Microsoft Windows. Apple's operating system is called macOS, and there is also an open source operating system called Linux.

OS/2
(Operating System 2) A rival PC operating system to Microsoft Windows, produced by IBM in the 1990s, now obsolete.

Overwrite Replace a computer file such as a document or picture with a newer version, destroying the earlier version. If you make changes to a document and save it with the same filename, the previous version is overwritten and usually cannot be restored.

P2P See peer-to-peer

Palmtop A small computer which fits into the palm of your hand. They run similar software to conventional PCs, but (unlike notebook PCs) are more limited in what they can do than desktop PCs, because of the constraints of miniaturisation. See PDA.

Parallel Port A special socket for plugging a printer into a computer, now obsolete.

Patch A program which makes updates to computer software, usually to fix bugs which had not been detected when the software went on sale. The best place to look for a patch is on the software manufacturer's website.

PAYG (Pay As You Go) A cellphone network connection where you add credit to the phone manually, rather than having a contract billed monthly.

PC (Personal Computer) Originally just short for "personal computer", PC is now an industry standard, partly evolved in the marketplace, partly agreed by a committee of the major players in the computer industry.

PCI (Peripheral Component Interconnect) A standard for PC expansion cards, currently the most popular in desktop PCs. A "PCI slot" is a socket on the motherboard for such cards.

PCI Express A special type of PCI slot for graphics cards, replacing AGP in most new computers.

PDA (Personal Digital Assistant) A small handheld computer used for taking notes on the move, keeping contact information and so on. See also palmtop.

PDF (Portable Document Format) A popular document format, often used for online computer manuals and copies of formal letters, which retains the look of a printed letter or book onscreen. PDFs are created using Adobe Acrobat, but can be read and displayed by many different programs.

Peripheral Anything that plugs into the computer, such as mouse, keyboard, printer etc.

Phishing An internet scam in which a forged message from a bank provides a link for you to go to their website and "confirm your details" - but the website is a fake, and if you do enter your details they will be used to steal your money. Note that a legitimate email from your bank will be addressed to you personally rather than "Dear customer" etc, and will never ask you to enter your PIN.

Pixel (PICture ELement) All computer screen or printed images are made up of pixels, small square dots - the smaller the pixels, the higher the image quality.

pixelated A picture that has been compressed so much that the pixels that make it up are large and visible to the naked eye, making the image look like it is made out of square blocks (which it is, but they shouldn't be visible).

Plasma A type of very large screen, either TV or computer monitor. No longer sold in most places as they use a lot of power.

Platform-independent If something is platform-independent, you don't need a particular type of computer or particular software to use it.

Podcast An audio file that can be downloaded to a portable audio player or computer or streamed, usually speech.

POP3 (Post Office Protocol version 3; pr. "pop 3") A protocol for transmitting and receiving email.

Pop-up A form of online advertising where the advert pops up in a separate window when you go to a particular webpage.

Port A socket on the back (usually) of a computer which allows you to plug in extra hardware such as a printer or modem.

POST (Power On Self Test; pr. "post") A routine PCs go through when first switched on, before loading the operating system, to make sure the hardware is working properly.

Power-on password A password which the computer will prompt you for whenever the computer is switched on, a good security measure provided you don't forget the password. Power-on passwords can usually only be bypassed by taking the computer to bits.

Powerpoint A very popular program for creating graphical presentations, mostly for business use. Available separately or as part of Microsoft Office.

Processor The nerve centre of the computer : everything flows through it. Also called the CPU. The most important single specification on any PC is the speed of its processor, usually measured in megahertz (MHz), or latterly gigahertz (GHz).

Program A program is essentially a list of instructions that tell a computer how to do something. Any word processor, spreadsheet, database, game or any other tool you may use on a computer is a program (or group of programs). Also referred to as software.

Protocol Any "language" used by computers to communicate with each other for particular tasks.

Proxy server A computer used to store copies of popular webpages at an ISP and provide them on request, to save having to fetch them from the website again.

PS2
A popular game console from the Sony Corporation

PVR
(Personal Video Recorder) A TV video recorder which records to a hard disk. Typically a standalone unit, but you can also get software which allows you to use your PC's hard disk for this purpose.

Quad-core PC processors which have four complete processors on the same chip, allowing computers to handle multiple tasks faster. See also dual-core.

Quicktime A video compression standard created by Apple, and the program which displays such movies. Usually Quicktime files have the extension .MOV.

RAID (Redundant Array of Inexpensive Disks; pr. "raid") A way of connecting multiple hard disks together so that a computer sees them as one very large, very fast disk instead of many smaller ones, or to add redundancy so that if any disk in the array is physically damaged, the others have a copy of all the data and nothing is lost. Often called a "RAID array", even though the acronym already contains the word array. Mostly used on network servers.

RAM (Random Access Memory; pr. "ram") The computer's main memory, which it uses to hold whatever you are currently working on. The contents of RAM are lost when the computer is switched off. Adding more RAM is often the most cost-effective upgrade for an ageing computer.

Readme An electronic document, usually distributed with software, containing additional information that didn't make it into the printed guides, often giving tips about troubleshooting installation problems, and last minute changes to the software. It is usually entitled "readme.txt".

Read-only A read-only file has been set so that it cannot be altered or deleted. Also called write-protected. You can make a file read-only in Windows by right-clicking on it and checking the "read-only" box under attributes.

Real Audio, Real Media, Real Video An audio and video compression system from RealMedia Inc which produces files small enough to play back in real time over an ordinary modem, at the cost of a lot of sound/vision quality. Now largely obsolete.

Reboot Restart the computer, either by shutting it down properly and restarting it (a soft reboot), or just switching it off and on again (a hard reboot - should only be used as a last resort).

Registrar

An organisation which retains a register of internet domain names, who owns them, and where they can be found. Domains under the most popular TLDs such as .com, .net and .org can be registered with a number of different competing registrars, but you only need to register with one of them. National domains such as .uk usually have only one registrar.

Registry A file on Windows PCs which contains all the settings for the PC and its software. Can be edited by the user, but this should only be done as absolutely a last resort, as it is possible to trash the operating system if you don't know what you are doing.

Resolution Loosely speaking, the quality of an image. When printing or working with images, the resolution is usually measured in Dots Per Inch (dpi) - the more dots per inch, the higher the quality of the image but the larger the file needed to store it. In Windows, the screen resolution is how many pixels fit on the desktop.

RGB (Red, Green, Blue) The three colours used by a computer screen - all the other colours can be made up by mixing red, blue and green. A few printers use this system as well, though most use the alternative CMYK system instead.

Ripper Program which copies ("rips") tracks from music CDs onto a computer, often as an MP3. Technically this is illegal in many jurisdictions, but in practice extremely widespread, and is usually tolerated as long as the ripped tracks are for personal use only.

ROFL (or ROTFL) (Rolling On the Floor Laughing) Internet slang indicating laughter.

ROM (Read Only Memory; pr. "rom") Memory whose contents are preset and cannot (usually) be changed by the user. See also CD-ROM.

Router The central piece of equipment which connects you to the internet on a broadband connection.

RPG (Role Playing Game) A computer game in which you control a character and interact with other characters, explore virtual worlds, undertake quests etc. See MMORPG.

RSS (Really Simple Syndication) An automated system for gathering information, usually news, from multiple sources and bringing it together in one place, usually a website. If any of the information is changed at the source, it is automatically updated at the target.

RTFM (Read The Flipping Manual) Internet slang, usually fired at people asking basic questions to which they would know the answers if they had looked at the manual. There are other translations of the letter F... :-)

RTS (Real Time Strategy) A computer game where you command armies (usually) of animated figures, direct their development, fight their battles and so on. "Real Time" because the game runs continuously rather than waiting for your orders, though in practise you can usually pause the game as much as you like unless you are playing against a human opponent.

That was M-R; click here for A-D (+ numbers); E-L; S-Z.

Didn't find what you were looking for? Sorry about that. Send an email to gloss13 at jonstorm.com and I'll try and include it in the next revision. Your feedback is much appreciated!

Sorry the above contact address isn't a nice clickable "mailto" link. It used to be, but clickable email addresses get auto-harvested by spammers, and bombarded with junk mail. Sometimes they even manually harvest the disguised address above, and start spamming that. It should be obvious that anyone going to the trouble of disguising their contact address like this is extremely unlikely to buy anything advertised via spam, but then most spammers aren't very bright.

Go to Dictionary A-D (+ numbers); E-L; S-Z; Absolute beginners' HTML; Jon Storm's website

It says...	It means...
Mac, Macintosh, Macbook	The Apple Corporation's alternative to the PC, much loved by its devotees. It is the only widely available personal computer that doesn't use Microsoft Windows. Most popular Windows software is also released in Mac format. The Macbook is a laptop.
Mac address	(Media Access Control) The unique serial number of an Ethernet card or other networking device. (Nothing to do with Apple Macs, despite the name). It is mostly used to identify which device is talking to which on a network, and is usually only needed when troubleshooting network problems. In the UK, a "MAC code" is a unique number used for switching broadband providers smoothly.
Macro	A small program used to automate repetitive or complex tasks.
Mailbomb	One or more very large emails, sent to someone maliciously to stop them being able to use their mailbox and/or internet connection, because all the available bandwidth is being used up downloading the mailbomb(s). See also DoS (Denial of Service).
Malware	A catch-all term for software installed by stealth onto a PC for malevolent purposes (hence the name). These may include displaying unwanted ads (adware), installing software you didn't ask for, or spying on your activities (spyware) and reporting them back to the culprit so that he can steal your bank account, address book etc.
Mbps	(MegaBits Per Second) A measure of speed of information flow over a network (and if it's measured in Mbps, it's reasonably quick.) A Megabit is one million bits. (Actually slightly more if you want to egt pedantic about it). See also bps, Kbps.
Megabyte	Unit of measurement for pieces of information : approximately 1 million bytes or a thousand kilobytes. Often shortened to Meg or just M. See also Gigabyte, Kilobyte, Byte.
MegaHertz	See MHz.
Megapixel	A million pixels. Often used to measure the quality of digital cameras : the higher the number the better the camera.
Memory	Also known as RAM. Where the computer holds whatever you are currently working on. The contents of memory are lost when the computer is switched off.
Meta	The company which owns popular social media sites Facebook and Instagram.
MFD	(Multi Function Device). A combined printer, scanner, photocopier and fax machine.
MHz	(Megahertz). Millions of cycles per second. Most often used as a measurement of a PC processor chip's speed and power, with bigger numbers meaning more speed and a higher price. See also GHz.
Micro-filter	A device which allows you to use an ordinary phone over a telephone line set up for an ADSL internet connection. Sometimes just called a filter.
Microsoft	The largest business software provider for desktop PCs and laptops, There best known software is Windows, now up to version 11, and Microsoft Office which includes Word, Excel, Access and Powerpoint, and Outlook, a combined mail and calendar program.
MIDI	(Musical Instrument Digital Interface; pr. "middy") A very popular standard for controlling musical instruments connected to computers. A MIDI file is a list of instructions to play particular notes at particular intervals in particular styles, not a sound recording.
MLM	(Multi-Level Marketing) A scam similar to pyramid selling, once much in evidence on the internet, particularly in spam. Despite the claims of those promoting MLM, it is of dubious legality in most jurisdictions.
MMORPG	(Massively Multiplayer Online Role-Playing Game). An online role-playing game (RPG) designed to played by thousands of players simultaneously.
Modem	(MOdulator/DEModulator) A device for allowing computers to communicate over a phone line, now largely obsolete.
Monitor	The screen of a PC.
Motherboard	The main circuitboard in the computer - all the other bits and pieces are plugged into it.
Mouse	A device used to move a pointer around on the computer screen. Essential to get the most out of Windows, though it is not quite impossible to use Windows without one.
MP3	(MPeg-1 audio layer 3). A very popular standard for compressing audio and particularly music files down to a reasonable size with little or no perceptible loss of quality, and the files created using it - "an MP3" is an audio file. See MPEG, Compression.
MPEG	(Motion Picture Experts Group; pr. "em-peg") A set of standards for compressing video and audio files, and the committee that came up with them. Also, often used to mean movie files created to the MPEG standard.
Nameserver	An internet server which translates the alphabetic web addresses favoured by humans into the numeric ones used by computers.
Napster	A pioneering peer-to-peer internet file-sharing system. Because much of the data shared was copyrighted, and thus being distributed illegally, the operators of Napster were hit with a number of large lawsuits by the music industry, and eventually closed down. The name was bought and is now used by a legal pay-to-download service.
Netbook	A smaller version of the popular laptop computer format.
Network	A way of linking several computers together so that their users can share resources such as printers and documents, often via a central computer called a server. See also LAN, WAN, Ethernet.
Network card, Network Interface Card	An Expansion card which lets a PC communicate with a network, required for broadband Internet access. See also Ethernet, NIC.
Newbie	(New beginner) Internet slang for someone who is new to using computers, the internet or a game.
Newsgroup (or just News)	A public area where you can read and post messages on a particular topic or theme, allowing public discussion, either on the Internet or a Bulletin Board. Largely replaced by internet forums.
NIC	(Network Interface Card) An Expansion card which lets a PC communicate with a network or use a broadband internet connection. Almost all modern NICs are Ethernet cards.
Noob	Someone who is new to a game or internet service, derived from newbie
Notebook	A portable PC, with system unit, screen and keyboard in one package. Also called a laptop.
OCR	(Optical Character Recognition) A program which attempts to convert a scanned image (ie a picture) of text into text that can be edited in a word processor. The result is rarely 100% accurate and must be carefully proofread, but it can save a lot of retyping.
OEM	(Original Equipment Manufacturer) A company that actually builds computers, as opposed to just retailing them. "OEM software" is ordinary software bought in bulk at a discount by the OEM and pre-installed on a new machines, usually without printed manuals. OEM software cannot legally be sold separately from a computer, so when offered for sale at huge discounts is either pirated, or not what it claims to be.
Office Suite	A related group of programs for business use, usually including a word-processor, spreadsheet, database and a number of other programs. The best known is Microsoft Office.
Off-topic	A message which is not relevant to a particular discussion, for example on social media. Posting off-topic messages annoys people and can make a discussion unreadable if there are a lot of them, so will often get the perpetrator banned.
Online	Connected to the internet, or of the internet.
Open Source	Software (usually) that is created and distributed with either relaxed or no copyright restrictions.
Operating System	Every computer has an operating system, which is a sort of master program that runs automatically when you switch the computer on, and continues running till you switch off. It is responsible for the many routine tasks required to keep a computer running : moving the pointer when you move the mouse, providing icons and menus, running other programs such as a word processor or a game which you may request, controlling the various disk drives, the screen and so on. The most widely used PC operating system is Microsoft Windows. Apple's operating system is called macOS, and there is also an open source operating system called Linux.
OS/2	(Operating System 2) A rival PC operating system to Microsoft Windows, produced by IBM in the 1990s, now obsolete.
Overwrite	Replace a computer file such as a document or picture with a newer version, destroying the earlier version. If you make changes to a document and save it with the same filename, the previous version is overwritten and usually cannot be restored.
P2P	See peer-to-peer
Palmtop	A small computer which fits into the palm of your hand. They run similar software to conventional PCs, but (unlike notebook PCs) are more limited in what they can do than desktop PCs, because of the constraints of miniaturisation. See PDA.
Parallel Port	A special socket for plugging a printer into a computer, now obsolete.
Patch	A program which makes updates to computer software, usually to fix bugs which had not been detected when the software went on sale. The best place to look for a patch is on the software manufacturer's website.
PAYG	(Pay As You Go) A cellphone network connection where you add credit to the phone manually, rather than having a contract billed monthly.
PC	(Personal Computer) Originally just short for "personal computer", PC is now an industry standard, partly evolved in the marketplace, partly agreed by a committee of the major players in the computer industry.
PCI	(Peripheral Component Interconnect) A standard for PC expansion cards, currently the most popular in desktop PCs. A "PCI slot" is a socket on the motherboard for such cards.
PCI Express	A special type of PCI slot for graphics cards, replacing AGP in most new computers.
PDA	(Personal Digital Assistant) A small handheld computer used for taking notes on the move, keeping contact information and so on. See also palmtop.
PDF	(Portable Document Format) A popular document format, often used for online computer manuals and copies of formal letters, which retains the look of a printed letter or book onscreen. PDFs are created using Adobe Acrobat, but can be read and displayed by many different programs.
Peripheral	Anything that plugs into the computer, such as mouse, keyboard, printer etc.
Phishing	An internet scam in which a forged message from a bank provides a link for you to go to their website and "confirm your details" - but the website is a fake, and if you do enter your details they will be used to steal your money. Note that a legitimate email from your bank will be addressed to you personally rather than "Dear customer" etc, and will never ask you to enter your PIN.
Pixel	(PICture ELement) All computer screen or printed images are made up of pixels, small square dots - the smaller the pixels, the higher the image quality.
pixelated	A picture that has been compressed so much that the pixels that make it up are large and visible to the naked eye, making the image look like it is made out of square blocks (which it is, but they shouldn't be visible).
Plasma	A type of very large screen, either TV or computer monitor. No longer sold in most places as they use a lot of power.
Platform-independent	If something is platform-independent, you don't need a particular type of computer or particular software to use it.
Podcast	An audio file that can be downloaded to a portable audio player or computer or streamed, usually speech.
POP3	(Post Office Protocol version 3; pr. "pop 3") A protocol for transmitting and receiving email.
Pop-up	A form of online advertising where the advert pops up in a separate window when you go to a particular webpage.
Port	A socket on the back (usually) of a computer which allows you to plug in extra hardware such as a printer or modem.
POST	(Power On Self Test; pr. "post") A routine PCs go through when first switched on, before loading the operating system, to make sure the hardware is working properly.
Power-on password	A password which the computer will prompt you for whenever the computer is switched on, a good security measure provided you don't forget the password. Power-on passwords can usually only be bypassed by taking the computer to bits.
Powerpoint	A very popular program for creating graphical presentations, mostly for business use. Available separately or as part of Microsoft Office.
Processor	The nerve centre of the computer : everything flows through it. Also called the CPU. The most important single specification on any PC is the speed of its processor, usually measured in megahertz (MHz), or latterly gigahertz (GHz).
Program	A program is essentially a list of instructions that tell a computer how to do something. Any word processor, spreadsheet, database, game or any other tool you may use on a computer is a program (or group of programs). Also referred to as software.
Protocol	Any "language" used by computers to communicate with each other for particular tasks.
Proxy server	A computer used to store copies of popular webpages at an ISP and provide them on request, to save having to fetch them from the website again.
PS2	A popular game console from the Sony Corporation
PVR	(Personal Video Recorder) A TV video recorder which records to a hard disk. Typically a standalone unit, but you can also get software which allows you to use your PC's hard disk for this purpose.
Quad-core	PC processors which have four complete processors on the same chip, allowing computers to handle multiple tasks faster. See also dual-core.
Quicktime	A video compression standard created by Apple, and the program which displays such movies. Usually Quicktime files have the extension .MOV.
RAID	(Redundant Array of Inexpensive Disks; pr. "raid") A way of connecting multiple hard disks together so that a computer sees them as one very large, very fast disk instead of many smaller ones, or to add redundancy so that if any disk in the array is physically damaged, the others have a copy of all the data and nothing is lost. Often called a "RAID array", even though the acronym already contains the word array. Mostly used on network servers.
RAM	(Random Access Memory; pr. "ram") The computer's main memory, which it uses to hold whatever you are currently working on. The contents of RAM are lost when the computer is switched off. Adding more RAM is often the most cost-effective upgrade for an ageing computer.
Readme	An electronic document, usually distributed with software, containing additional information that didn't make it into the printed guides, often giving tips about troubleshooting installation problems, and last minute changes to the software. It is usually entitled "readme.txt".
Read-only	A read-only file has been set so that it cannot be altered or deleted. Also called write-protected. You can make a file read-only in Windows by right-clicking on it and checking the "read-only" box under attributes.
Real Audio, Real Media, Real Video	An audio and video compression system from RealMedia Inc which produces files small enough to play back in real time over an ordinary modem, at the cost of a lot of sound/vision quality. Now largely obsolete.
Reboot	Restart the computer, either by shutting it down properly and restarting it (a soft reboot), or just switching it off and on again (a hard reboot - should only be used as a last resort).
Registrar	An organisation which retains a register of internet domain names, who owns them, and where they can be found. Domains under the most popular TLDs such as .com, .net and .org can be registered with a number of different competing registrars, but you only need to register with one of them. National domains such as .uk usually have only one registrar.
Registry	A file on Windows PCs which contains all the settings for the PC and its software. Can be edited by the user, but this should only be done as absolutely a last resort, as it is possible to trash the operating system if you don't know what you are doing.
Resolution	Loosely speaking, the quality of an image. When printing or working with images, the resolution is usually measured in Dots Per Inch (dpi) - the more dots per inch, the higher the quality of the image but the larger the file needed to store it. In Windows, the screen resolution is how many pixels fit on the desktop.
RGB	(Red, Green, Blue) The three colours used by a computer screen - all the other colours can be made up by mixing red, blue and green. A few printers use this system as well, though most use the alternative CMYK system instead.
Ripper	Program which copies ("rips") tracks from music CDs onto a computer, often as an MP3. Technically this is illegal in many jurisdictions, but in practice extremely widespread, and is usually tolerated as long as the ripped tracks are for personal use only.
ROFL (or ROTFL)	(Rolling On the Floor Laughing) Internet slang indicating laughter.
ROM	(Read Only Memory; pr. "rom") Memory whose contents are preset and cannot (usually) be changed by the user. See also CD-ROM.
Router	The central piece of equipment which connects you to the internet on a broadband connection.
RPG	(Role Playing Game) A computer game in which you control a character and interact with other characters, explore virtual worlds, undertake quests etc. See MMORPG.
RSS	(Really Simple Syndication) An automated system for gathering information, usually news, from multiple sources and bringing it together in one place, usually a website. If any of the information is changed at the source, it is automatically updated at the target.
RTFM	(Read The Flipping Manual) Internet slang, usually fired at people asking basic questions to which they would know the answers if they had looked at the manual. There are other translations of the letter F... :-)
RTS	(Real Time Strategy) A computer game where you command armies (usually) of animated figures, direct their development, fight their battles and so on. "Real Time" because the game runs continuously rather than waiting for your orders, though in practise you can usually pause the game as much as you like unless you are playing against a human opponent.