What did he say???
Computer jargon explained.

Compiled by Jon Storm.
2015 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. The Windows equivalent is a wizard.
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). Most ISPs will close down any account responsible for mailbombing. 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.
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.


(Microcomputer) When desktop computers first appeared in the 1970's, they were often called microcomputers, later shortened to micro, to distinguish them from the so-called minicomputers of the day, which far from sitting on a desk were a good deal bigger than it! There was also a popular early home computer in the UK called the BBC Micro, now long obsolete.
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.


The largest business software provider for desktop PCs and laptops, and the only major operating system provider apart from Apple, they created Windows, Microsoft Office (which includes Word, Excel, Access and Powerpoint), Internet Explorer, Outlook and many other widely used programs. They are belatedly moving into the tablet and phone markets too, but they are way behind in these markets, and their first attempt to create a unified Windows for all devices, Windows 8, was a bit of a disaster.

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.
MIME (Multipurpose Internet Mail Extension; pr. "mime") An encoding system used in email, mainly for sending attachments. Email was originally designed to just use plain text, so programs, graphics etc have to be sort of disguised as text for email systems to be able to handle them. MIME is more powerful than its predecessor, UUENCODE (pr. you-you-encode), but not all systems accept it.
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, such as Everquest or Warcraft.
Modem (MOdulator/DEModulator) A device for allowing computers to communicate over a phone line.
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 later 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 hasn't been using computers or the internet long.
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.
Notebook A portable PC, with system unit, screen and keyboard in one portable 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 newsgroup or forum on the Internet is said to be "off-topic". Posting off-topic messages in newsgroups annoys people intensely, as they make it harder to follow the discussion properly.
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.


(Operating System 2) A rival PC operating system to Microsoft Windows, produced by IBM in the 1990s. It still has a small, dedicated core of supporters, but didn't catch on and for most purposes is 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. The computer usually refers to the parallel port as LPT1.
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.
PC 2005 (2004, 2003 etc) An agreed standard for new PCs, set each year 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.
PCMCIA (Personal Computer Memory Card International Association) A type of PC expansion card, the size of an ordinary credit card, mainly intended for use with notebooks.
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, used mainly for online computer manuals, which retains the look of a printed book onscreen. PDFs are created using Adobe Acrobat, but can be read and displayed by many different programs including Internet Explorer.
Peer-to-peer A type of network where computers are connected together directly, rather than via a server, allowing them to access each other's hard disk etc. Most home networs work like this.
Pentium The best known PC processor (or CPU), manufactured by Intel.
Peripheral Anything that plugs into the computer, such as 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 all your money. Note that a legitimate email from your bank should 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.
Platform-independent If something is platform-independent, you don't need a particular type of computer or particular software to use it. For example is the internet, which you can access from a PC, Mac, tablet or any smartphone.


(Plug and Play) A system where Windows automatically detects any new hardware that is plugged into the PC and adjusts to it without human intervention.
Podcast An audio file that can be downloaded to a portable audio player or computer, 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 browser window when you go to a particular webpage. Many people find it intensely irritating, and some browsers now have the ability to block pop-ups from opening.
Port A socket on the back (usually) of a computer which allows you to plug in extra hardware such as a printer or modem.
Portal A virtual gateway between computer systems, or a website that provides links to lots of useful sites on a particular theme, eg shopping or news.
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, Microsoft's office suite.
Processor The nerve centre of the computer : everything flows through it. Also called the CPU. The best known is Intel's Pentium series. 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 (often a 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.

The type of connector used to plug in mouse and keyboard on most modern PCs, now gradually being superseded by USB. PS/2 was originally the name of a PC from IBM with a number of innovative but non-standard features, including special connectors for mouse and keyboard. The PC didn't catch on particularly well, mainly because its unusual architecture meant that it could not accept standard expansion cards, but its mouse and keyboard connectors proved popular and were widely adopted.

PS2 (without the /) is often used to refer to Sony's PlayStation 2, a popular games console.


(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. Floppy disks can be write-protected by moving a small plastic square in the top left corner. Files on CD ROM are always read-only because you can't change the contents of a CD ROM.

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.
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).


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, the most popular being 800 x 600 and 1024 x 768 - the former makes images, icons etc look bigger, but the latter means you can fit more of them on the screen.
Rewriteable A special type of reuseable CD or DVD which you can write to, delete the contents, and write to again, theoretically forever. (A conventional CD or DVD's contents can't be changed once they have been written). However, rewriteable CDs are less reliable and more expensive than write-once CDs, and there are presently several different incompatible formats for rewriteable DVDs.
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 A device used to connect networks together, for example so that several PCs can share one internet connection. A relative of the hub, but more powerful.
RPG (Role Playing Game) A computer game in which you control a character and interact with other characters, explore virtual worlds, undertake quests etc, often involving swords and sorcery. 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 several different 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.

Copyright © Jon Storm 2000-2015.
Last update : 27 February 2015

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