Advanced Graphics Port. Graphics card interface for high performance graphics (faster than PCI). Specification Denoted Notes AGP 1.0 AGP AGP x1 AGP x2 Supports 1x and 2x adapter cards. Uses a signal level of 3.3 volts. AGP 1.0 adapter cards have a different slot arrangement from AGP 2.0 (and later) and therefore an AGP 1.0 adapter card will not fit into an AGP 2.0 slot. AGP 2.0 AGP x4 Supports 4x adapter cards, i.e. 4 times faster than the original AGP specification. Uses a signal level of 1.5 volts. AGP 3.0 AGP x8 Supports 8x adapter cards. Uses a signal level of 0.8 volts. The slot for AGP 3.0 is identical to that for AGP 2.0. AGP 2.0 and AGP 3.0 cards and motherboards should be compatible with each other - but an AGP 8x card fitted to a motherboard that only supports AGP 4x will be forced to work at the slower 4x rate.

American Standard Code for Information Interchange. In ASCII the letters of the alphabet, digits and various punctuation symbols are assigned a unique 7 bit number (0-127). cf Unicode.

On most systems there is also an additional set of 128 "extended ASCII codes" that are used to represent a variety of other symbols. These extended codes are not part of the ASCII standard.

1. A recovery system or means to recover in the event of a disaster.

   1. To take a copy of files (directories or data) so that these can be restored later if needed. Backups should always be taken regularly to protect against accidental deletion of files or hardware failure.

   Many applications generate a backup file as they work. For example most work processors can be configured to generate a backup file of the document they are working on, allowing the previous version to be recovered if necessary. However this type of backup will not protect against hardware failure, if the disk fails then you loose your original and the backup.

   A good backup scheme will ensure that files are copied to a separate medium (such as cd or tape) and physically moved to a different area, ideally to a different site. Moving a backup (or a copy of a backup) to an offsite location is referred to as an "offsite backup", and the advantage of maintaining an "offsite backup" is that it allows files to be recovered in the event of a disaster such as a fire that may destroy the entire building.

   1. The copy of a file (or set of files or data) that has been taken. A backup may therefore be the copy of a file or it may refer to a disk, cd or tape that contains files (or data) that have been backed up.

Basic Input/Output System. The BIOS provides an interface between a computer's operating system and the computer's hardware. Unlike the operating system the BIOS is built into the computer and thus is always available. Many computers hold the BIOS in Flash and allow it to be upgraded.

The BIOS will normally perform various diagnostic tests straight after power-up (see POST). At this point it is usual for a BIOS to allow you to enter a "BIOS Screen" to configure aspects of the BIOS (not every BIOS supports this). Whilst each BIOS may have a different way of invoking its "BIOS Screen" and the correct method should be stated in the manual, the following key combinations (at start-up) are common:

* DEL
* F2
* F1

Terminal error screen displayed by Microsoft Windows, not normally recoverable except by a reboot. Also known as BSOD or a Stop Screen. A blue screen will display a STOP error code, which may give some indication as to the cause.

1. Compact Disc. CDs typically contain audio (Audio-CD), video (Video-CD) or data (CD-ROM).

Audio CDs contain audio sampled at 16-bit, 44.1kHz and provides 74 or 80 minutes of two-channel (stereo) audio.

CD-ROMs can store up to 650MB of data.

1. Change Directory. The cd command is a command-line command to change the current directory. It is available on a number of operating systems (including Windows and Unix/Linux.) The 'cd' command is normally expressed in lower case.

2. Abbreviation for candela, the SI unit for the luminous intensity of light.

CD-Readable-Writable. A compact disc (CD) which can be recorded to and overwritten many times. cf CD-R.