Computer Terminology - Some Common Terms Explained

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Can't tell your RAM from your ROM? What size HDD do you want, and what OS do you want installed on it? Why 'Notebook' not 'Laptop'? Why "Program" and not "Programme"? Why is 'Windows' called "Windows"? - all that sort of stuff...

Hopefully we won't slip into jargon, but here are a few terms explained...  

Computer Components a logical, if not alphabetical, order

The case that contains all the other components - what most people actually call 'The Computer'


Power Supply Unit. This is where your computer plugs into the mains, and is what distributes power to the Motherboard


The central printed circuit board (PCB) in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple computers (you've heard of them?), the logic board. It is also sometimes casually shortened to mobo.

Hard Drive

A hard disk drive (often shortened as "hard disk", "hard drive", or "HDD"), is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to a device distinct from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit (except for a filtered vent hole to equalize air pressure) with fixed media. Non- volatile means that the data remains in memory even when the computer is switched off, and so is available next time it's switched on. Typically, the storage space is measured in Gigabytes, or increasingly, Terabytes. A typical PC will have a HDD of between 250 - 500 GB

Also referred to as the CPU (Central Processing Unit). An electronic circuit that can execute computer programs. Effectively it performs millions of mathematical calculations (by reading the code that programs are written in) a second and tells the computer how to work.

Memory (RAM)

Random Access Memory - this is 'volatile' memory and is cleared when the PC is switched off. It is used to run programs and a typical modern PC will have between 2GB and 4GB RAM
Optical Drive
An additional drive used to play DVD, CD or Blu-Ray Discs. Called "Optical" as the drive uses laser light through a lens to read the discs. More commonly referred to as  the 'DVD (or CD, or Blu Ray) Drive"
Expansion Cards

An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard to add additional functionality to a computer system. You can get all sorts of cards that will, for example, provide additional USB or Firewire ports, or almost anything, but probably the most common are Sound Cards or Graphics Cards. The most popular current format for expansion cards is known as PCI-e or PCI (Peripheral Component Interconnect) Express
Sound Card

A sound card (also known as an audio card) is a computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. Most modern motherboards come with 'On Board' sound of a very high quality and it's only if you really require High Fidelity sound that you should need to add a sound card.
Graphics Card
Also called a video card, graphics accelerator card, display adapter, or graphics card, is an expansion card whose function is to generate and output images to a display. Probably a more common addition these days than a Sound Card, Graphics Cards offer very high quality display options essential in Graphic Design or Gaming.


The screen that displays the data (programs, pictures, games etc.). These are usually TFT (Totally Flat Tube) or LCD (Liquid Crystal Display) format and common sizes range between 17" and 24" (although smaller and larger screens are available). When referring to size, this is measured diagonally from corner to opposite corner.
Operating System

The software or program that 'runs' the computer -it tells all the other components and programs how to work. Often abbreviated to OS. The most common OS in use today is Microsoft Windows ™®.


Universal Serial Bus - a serial bus standard to connect devices to a host computer. A 'bus' is a subsystem that transfers data between computer components inside a computer or between computers. The most common way to connect external devices or 'peripherals' to a computer.
RAM Random Access Memory. Not used for storage, but to run programs, this is 'volatile' memory - it's cleared each time the computer is switched off
ROM Read Only Memory. Memory that cannot be changed by the user - This tells the computer how to load the operating system.
CD Compact Disc
DVD Digital Versatile Disc
HDD Hard Disc Drive (see above)
TFT Totally Flat Tube (as in monitors, above)
LCD Liquid Crystal Display (ditto)
DVD-R, DVD-RW DVD - Recordable - you can record once. DVD - Rewritable - you can change the content.

Asymmetric Digital Subscriber Line - Broadband. It's 'Asymmetric' as the Download speed (the transfer rate from the Internet to your computer) is at a different (higher) speed than the Upload (the rate that your computer will transfer data to the Internet).

'Laptop' or 'Notebook' ? And what's a 'Netbook'?

A Laptop (as the name implies) is a portable computer that you can operate whilst resting it on your lap. Originally a "Notebook" was a smaller "Laptop" that had, possibly a smaller screen and/or no internal Optical Drive. However, the division between the two 'greyed' and so generally the terms became interchangeable, and to a certain extent still are.

As "Laptops" became more powerful, they started getting hotter (processors run very hot when they're working hard) and it became more and more uncomfortable to actually use your laptop on your lap (manufacturers even got sued for some allegedly really serious injuries). Because of this 'laptop' became less descriptive as to the way you could use it, and manufacturers became sensitive to the term as it implied you could use it on your lap, which in a lot of cases you can't - so many now use the term "Notebook". Use either - we'll know what you mean!

A "Netbook" is a Notebook computer designed for wireless communication and access to the Internet. It is a combination of the words InterNET and NoteBOOK. Primarily designed for web browsing and e-mailing, Netbooks rely heavily on the Internet for remote access to web-based applications and are targeted increasingly at cloud computing (where programs are accessed over the Internet rather than being installed on the computer itself) and consequently can be less powerful. Netbooks typically run either Windows XP or Linux operating systems rather than more resource-intensive operating systems like Windows Vista. However Windows 7 has seen some features that have been shown to run well on the newer generation of Netbooks being released currently. The devices range in size from below 5 inches to over 13, typically weigh about 1 Kg and are often significantly cheaper than general purpose Notebooks at around £200, with some even given away for free by Internet Service Providers and Mobile Phone Providers if you sign up for Mobile Broadband with them.

Why "Program" and not "Programme"?

"Program" is the American "English" spelling that has been adopted more and more in the UK when specifically referring to Computer Programs (many software programs come from the U.S., so it makes sense). In English "English" it has the advantage that we can differentiate between what we have on our PC and what we watch on the Tellie...although with Internet TV you can watch a programme using a program.

Why 'Windows'?

Microsoft's original OS was known as Microsoft Disk Operating System - or MS-DOS. You didn't see much - basically a single colour screen with contrasting colour text and very limited text style. There was little, if any, graphical representation, and you could only run one program at a time.

To improve on this Microsoft developed the GUI (pronounced Gooey) or Graphical User Interface, which is what you see every time you use a modern computer. It allows more than one program, or multiple aspects of the same program (different Word Documents for example) to run at the same time. Each element has it's own screen or 'Window' in the GUI - you could say it's a 'Window' into the computer.


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