File.  A named collection of data (such as a computer program, document, or graphic) that exists on a storage medium such as a hard disk, floppy disk, or CD-ROM. 160
Information.  The words, numbers, and graphics used as the basis for human actions and decisions. 160
File naming conventions.  A set of rules, established by the operating system, that must be followed to create a valid filename. 161
Filename.  A unique set of letters and numbers that identifies a file. 161
Filename extension.  A set of letters and/or numbers added to the end of a filename that helps to identify the file contents or file type. 161
Wildcard character.  A symbol, such as an asterisk, used to represent a group of characters in a filename (for example, *.exe means all files with an exe extension). 162
Executable file.  A file, usually with an exe extension, containing instructions that tell a computer how to perform a specific task. 163
Data file.  A file containing words, numbers, and/or pictures that the user can view, edit, save, send, and/or print. 164
Generic filename extension.  A filename extension, such as bmp or txt, that indicates the type of data that a file contains, but does not indicate the specific program that was used to create the file. 165
Application-specific filename extension.  A file- name extension that is associated with the files created using a specific software program, such as the doc extension associated with Microsoft Word files. 166
Device letter.  The unique character by which each of the computer's storage devices can be identified. For example, the floppy disk drive is usually assigned device letter A. 168
File manager utility software.  Software, such as Windows Explorer, that helps users locate, rename, move, copy, and delete files. 168
Directory.  A list of files contained on a computer storage device. 169
Folders.  The subdirectories (a subdivision of a directory) that can contain files or other folders. 169
Root directory.  The main directory of a disk. 169
File specification.  A combination of the drive letter, subdirectory, filename, and extension that identifies a file (for example, A:\word\filename.doc). Also called a "path." 170
Bit.  A bit is the smallest unit of information handled by a computer. A bit can hold one of two values, either a 0 or a 1. Eight bits comprise a byte which can represent a letter or number. 174
Byte.  An eight-bit unit of information that represents a single character. 174
Storage device.  A mechanical apparatus that records data to and retrieves data from a storage medium. 174
Storage technology.  A term used to describe a storage device and the media it uses. 174
Magnetic storage.  The recording of data onto disks or tape by magnetizing particles of an oxide- based surface coating. 175
Read-write head.  The mechanism in a disk drive that magnetizes particles on the storage disk surface to write data, or senses the bits that are present to read data. 175
Optical storage.  A means of recording data as light and dark spots on a CD, DVD, or other optical media. 176
Cluster.  A group of sectors on a storage medium that, when accessed as a group, speed up data access.177
File allocation table (FAT).  A special file that is used by the operating system to store the physical location of all the files on a storage medium, such as a hard disk or floppy disk. 177
Sectors.  Subdivisions of the tracks on a storage medium that provide a storage area for data. 177
Tracks.  A series of concentric or spiral storage areas created on a storage medium during the for- matting process. 177
Defragmentation utility.  A software tool used to rearrange the files on a disk so that they are stored in continuous clusters. 179
Fragmented.  When data in a file is stored in non- contiguous clusters. 179
Undelete utility.  An operating system subcomponent, that, in some cases, allows the user to retrieve all or part of a deleted file. 179
Access time.  The estimated time for a storage device to locate data on a disk, usually measured in milliseconds. 180
Data transfer rate.  The amount of data that a storage device can move from a storage medium to computer memory in one second. 180
Gigabyte.  (GB) Approximately one billion bytes; exactly 1,073,741,842 bytes. 180
Kilobyte.  (KB) Approximately one thousand bytes; exactly 1,024 bytes. 180
Megabyte.  (MB) Approximately one million bytes; exactly 1,048,576 bytes. 180
Random access.  The ability of a storage device (such as a disk drive) to go directly to a specific storage location without having to search sequentially from a beginning location. 180
Sequential access.  A form of data storage, usually on computer tape, that requires a device to read or write data one record after another starting at the beginning of the medium. 180
Storage capacity.  The maximum amount of data that can be recorded on a storage medium, usually measured in kilobytes, megabytes, gigabytes, or terabytes. 180
Terabyte.  Approximately one trillion bytes. 180
Disk density.  The closeness of the particles on a disk surface. As density increases, the particles are packed more tightly together and are usually smaller. 181
Double-sided (DS) disk.  A, floppy disk that stores data on both the top and bottom sides of the disk. 181
High-density (HO) disk.  A floppy disk that can store more data than a double-density disk. 181
Zip disk.  A high-capacity floppy disk manufactured by Iomega Corporation, frequently used for back- ups. 181
Double-density (OD) disk.  A type of floppy disk with a higher storage capacity than single-density disks due to increased disk density. 182
Cylinder.  A vertical stack of tracks on a hard disk. 183
Hard disk.  One or more hard disk platters and their associated read-write heads (often used synonymously with hard disk drive). 183
Hard disk platter.  The component of the hard disk drive on which data is stored; a flat, rigid disk made of aluminum or glass and coated with a magnetic oxide. 183
Disk cache.  Part of RAM used to temporarily hold information read from a disk, speeding up processing. 185
Head crash.  A collision between the read-write head and the surface of the hard disk platter, resulting in damage to some of the data on the disk. 185
RAID (Redundant Array of Independent Disks).  Disks used by mainframes and microcomputers, in which many disk platters are used to provide data redundancy for faster data access and increased protection from media failure. 185
Removable hard disks.  Hard disk cartridges that contain platters and read-write heads, and that can be inserted into and removed from the hard drive. 185
Tape backup.  A copy of data from a computer's hard disk, stored on magnetic tape and used to restore lost data. 186
Open reel tapes.  Large spools of computer tape that are sometimes used as a distribution medium for mainframe and minicomputer systems.187
Tape cartridge.  A removable magnetic tape module, similar to a cassette tape. 187
CD-ROM.  A storage device that uses laser technology to read data from a CD-ROM. 188
Read-only.  An indication that a computer can retrieve data from a storage medium such as a CD-ROM, but cannot write new data onto it. 188
Archiving.  The process of moving infrequently- used data off a primary storage device to a storage medium such as a CD-ROM. 189
CD-R.  An acronym for compact disc-recordable. CD-R is a type of optical disk technology that allows the user to create CD-ROMs and audio CDs. 189
CD-RW.  An acronym for compact disc-rewritable. CD-RW is a type of optical disk technology that allows the user to write data onto a CD, then change that data much like on a floppy or hard disk. 189
Multisession support.  Allows a CD device to write data during more than one session or read data that has been written on a CD during more than one session. 189
Phase change technology.  A CD and DVD technology that uses disks with a modifiable crystal structure and allows users to add, modify, and delete data. 189
DVD+RW.  A DVD technology that allows users to record and change data on DVD disks. 190
DVD-RAM.  A blend of technologies that allow users to record data on a DVD disk. 190
DVD-ROM.  A DVD disk that contains data that has been permanently stamped on the disk surface. 190