Appendix
Glossary of Data Recovery Terms
ABEND: The abnormal termination of a computer program.
ABIOS: The ABIOS is a protected-mode BIOS which is used by OS/2.
Access: To locate the desired data.
Access Arm: The disk-drive component used to position read/write heads over a specified track.
Accessibility: The extent to which computers are easy to use and available to a wide range of users, including people with one or more physical disabilities.
Access Methods: The technique and/or program code for moving data between main storage and Input/Output devices.
Access Time: The time interval between when data is called for or requested to be stored in a storage device and when delivery or storage is completed.
Address Bus: The electrical pathway used to transmit the storage locations for data or instructions.
Address Translation: The process of changing the address of an item of data or an instruction to the address in main storage at which it is to be loaded or reloaded.
ADP: Automatic data processing.
Anticipatory Retrieval: A technique for optimizing the reading of data from a slow storage device by fetching more data than is immediately required and by retaining it in faster medium until it is actually needed.
ANSI: American National Standards Institute.
API: A set of routines that an application program uses to request and carry out lower-level services performed by the operating system.
Architecture: The structure of all or part of a computer system. Also refers to the design of system software.
ASCII: Acronym for American Standard Code for Information Interchange
ASCII Character: The most widely recognized 8 bit code for representing alphanumerics and other characters of English language.
ASCIIZ String: Sequence of ASCII Characters terminated by a Null, or zero, byte.
ASPI: Advanced SCSI Programming Interface.
ATA: Advanced Technology Attachment, the more correct name for the IDE interface.
Auxiliary Storage: Storage that supplements the primary storage of the computer, same as secondary storage.
Backup: The copying of information to provide a means of recovery from lost or corrupt data.
Backup File: A duplicate copy of a file.
BCD (Binary Coded Decimal): A method of data storage where two decimal digits are stored in each byte, one in the upper four bits and the other in the lower four bits. Since only the values 0 through 9 are used in each half of a byte, BCD values can be read as decimal numbers on a hexadecimal display of memory or a file.
Binary: Pertaining to characteristics or property involving a selection, choice, or condition in which there are two possibilities, or pertaining to the number system that utilizes a base of two.
Binary Digit: Either of the characters 0 or 1. These characters are abbreviated “bit”.
Binary Number System: A number system with a base or radix of two.
Binary System: The base 2 numbering system, which uses the digits 0 and 1. The computer data can be represented by this numbering system.
BIOS: Basic I/O system. A set of routines that works closely with the hardware to support the transfer of information between elements of the system, such as memory, disks, and the monitor.
BIOS Parameter Block (BPB): Information located inside the boot sector specific to the logical drive information.
Block: A grouping of contiguous data records or other data elements that are handled as a unit.
Block device: A device such as a disk drive that moves information in groups of bytes (blocks) rather than one byte at a time.
Block Editing: A capability of word processing programs that allows users to define, move, delete, or perform other operations on a block of text.
Blocked Tape: A storage technique used where records are grouped together on tape. This provides more storage and faster access by reducing the number of inter-record gaps.
Blocking Factor: The number of logical records combined into one physical record or block.
Boot: To start up the computer or operating system. The term "boot" is a contraction of "bootstrap", which in turn comes from the expression "to lift oneself by one's boot straps." The ROM BIOS on IBM PCs and compatibles reads in the first sector of the disk, which contains a short program of 512 bytes that reads in a portion of the operating system, which in turn reads in the remainder of the operating system.
Boot Drive: The disk drive from which the operating system was booted.
Boot sector: First sector on a logical drive that includes code to boot that drive, specific logical drive information, and error messages.
Bootstrap: A technique in which the first few instructions of a program are sufficient to bring the rest of itself into the computer from an input device.
Bottom Up Testing: Testing a computer program by beginning with individual subroutines or modules and then testing increasingly larger units.
Branch: A transfer of control from one instruction to another in a program that is not part of the normal sequential execution of the instructions of the program.
Breakpoint: When debugging, a memory location which when accessed causes a break in the normal flow of execution and the invocation of the debugger.
Bubble Memory: A type of nonvolatile memory where data are represented by the presence or absence of magnetized areas (bubble) formed on a thin piece of garnet.
Buffer: Temporary storage used to compensate for a difference in rate of flow of data, or time of occurrence of events, when transmitting data from one device to another.
Bug: A euphemism for a defect.
Bus: A set of hardwire lines used for data transfer among the components of a computer system.
Byte: A set of 8 binary digits.
C: A low-level structural programming language developed by AT&T-Bell Laboratories. It resembles a machine-independent assembler language and is popular for software package development.
Cache: Caching is a method of increasing performance by keeping frequently used data in a location which is more quickly accessed.
Cache Memory: A high-speed temporary storage area in the CPU for storing parts of a program of data during processing.
Call: A transfer of program control to a subroutine.
Capacity Management: The use of planning and control methods to forecast and control information processing job loads, hardware and software usage, and other computer system resource requirements.
Cartridge Tape: A form of magnetic tape similar to cassette tape but with a much greater storage density. Used mainly with large computer system.
Cassette Tape: A form of magnetic tape, about one fourth inch wide, generally used for secondary storage with microcomputers.
CBIOS: The CBIOS is a real-mode BIOS which is compatible with the earlier products in the IBM PC family and PS/2 models with 8086 processors.
CDFS: CD-ROM file system, which controls access to the contents of CD-ROM drives.
CD-ROM: Compact disc read-only memory. It is a laser-encoded optical memory storage medium.
Checksum: A calculated value used to test data for the presence of errors that can occur when data is transmitted or when it is written to disk.
Clean boot: Booting or starting a computer using the minimum system files in the operating system.
Clean installation: Installation of an operating system on a new computer or a computer with a reformatted hard disk.
Cluster: A specified number of sectors grouped together by the FORMAT command. The number and size is determined by the size of the logical drive. A cluster is the smallest storage unit for storing files.
CMOS: Complementary Metal-Oxide-Semiconductor, A type of integrated circuit design known for its low power consumption.
CMOS RAM: A small amount (typically 64 or 128 bytes) of memory in real-time clock chip of system that is preserved by the clock's battery and is used for storing configuration information.
Code: computer instructions.
COM (Computer Output Microfilm): A technology that permits the output information produced by computers to be store on microfilm.
Command Mode: A mode of operation in which application program commands can be selected.
Complier: A program that translates a high-level programming language into a machine language program.
Compressed Volume File (CVF): A file with read-only, hidden, and system attributes, and that contains a compressed drive.
Computer Virus: A program that copies its destructive program routines into the computer systems of anyone who accesses computer systems which have used the program, or anyone who use copies of data or programs taken from such computers. This spreads the destruction of data and programs among many computer users.
Computer: A device that can accept data, perform certain functions on that data, and present the results of those operations.
Copy: (1) The process of making a duplicate files from an existing file. (2) The process of duplicating text or graphics on the screen for placement elsewhere while leaving the original text or graphics intact.
Corrective Maintenance: Maintenance done for the purpose of eliminating a problem. It may occur as either emergency maintenance or deferred maintenance.
Crash: A hardware or software failure that leads to an abnormal cessation of processing.
Current Directory Structure: The data record used by DOS to keep track of the current directory on a drive, whether the drive is valid, network, Substituted, or Joined and other pertinent information.
Cursor: A movable point of light displayed on most video display screens to assist the user in the input of data.
Cut and Paste: A feature in an application software package that cuts (erases) part or all of an object or text and places it in a buffer. The object or text may be pasted (inserted) at a later time.
Cylinder: The set of concentric tracks of data located at the same position on each data-bearing surface of the disk. A double-sided floppy will contain two tracks per cylinder.
DASD: Acronym for direct-access storage device.
Data: Facts or observations about physical phenomena or business transactions.
Data Access Diagram: A graphic tool for depicting the ways by which a data store can be referred to by means of the information contained in another data store.
Data Administration: A data resource management function, which involves the establishment and enforcement of policies and procedures for managing data as strategic corporate resource.
Data Compression: A technique that saves storage space by eliminating gaps, empty fields, redundancies, or unnecessary data to shorten the length of records or blocks.
DDE: Dynamic Data Exchange. An interprocess communication method that allows two or more programs running simultaneously to exchange data and commands.
DDI: Device driver interface.
Debug: The detect, locate, and remove errors from a program or malfunctions from a computer.
Debugging: The process of removing defects from a computer system.
Decimal System: The base 10 numbering system using the digits 0 through 9.
Default Data: Values that are automatically provided by software to reduce keystrokes and to improve the productivity of computer user. However, the user has the option of replacing default data with other values when such action is needed.
Default Setting: In application software, a parameter that is automatically entered unless changed by the user.
Delayed Write: A form of caching in which control is returned before the data is actually written to the storage media.
Delete: An application-software feature that allows existing text, data, fields, records, or files to be removed.
Demand paging: A method by which code and data are moved in pages from physical memory to a temporary paging file on disk.
Device Driver: An interface module between the device-independent portions of the operating system and an actual hardware device which converts device-independent requests into the actual sequence of device operations to perform the requested action.
Device node: The basic data structure for a given device, built by Configuration Manager; sometimes called devnode. Device nodes are built into memory at system startup for each device and enumerator with information about the device, such as currently assigned resources. The complete representation of all device nodes is referred to as the hardware tree.
Direct Access Storage Device (DASD): A storage device that can directly access data to be stored or retrieved, for example, a magnetic disk unit.
Direct Access: A method of storage where each storage position has a unique address and can be individually accessed in approximately the same period of time without having to search through other storage positions.
Direct Memory Access (DMA): A method whereby peripherals may transfer data into or out of main memory without the involvement of the CPU.
Distribution media format (DMF): A special read-only format for 3½ inch floppy disks that permits storage of 1.7 MB of data.
Dock: To insert or remove a device in a computer system.
Disk Operating System (DOS): An operating system for microcomputers in which all or part resides on a disk and must be loaded into the computer. It is a set of programs that controls and supervises the microcomputer’s hardware.
DOS Extender: A program, which allows a program to run in protected mode while still retaining access to real-mode MSDOS services.
DRAM (Dynamic Random Access Memory): RAM memory, which essentially consists of a tiny capacitor for each bit of memory. Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents. Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses, which are accessed, so DRAM is slower than SRAM.
Dump: To copy the contents of all or part of a storage device, usually from an internal device, onto an external storage device.
DVD: Digital Versatile Disk. The optical disk storage that encompasses audio, video, and computer data.
EEPROM: A type of memory that can be erased and reprogrammed electrically without removing the chip from the circuit board.
Encryption: A way of making data indecipherable to protect it from unauthorized viewing or use.
EPROM: A type of memory that can be erased by removing it from the circuit and exposing the chip to ultraviolet light. It can then be reprogrammed.
Exception handling: An event that occurs as a program runs and that requires software outside the normal flow of control to be run.
Expanded Memory Specification: A specification devised by Lotus, Intel, and Microsoft for accessing more than one megabyte of memory by bank-switching additional memory into the one megabyte real mode address space.
Extended BIOS Data Area: A block of memory, typically the 1K at the top of conventional memory, which is used to store additional data for use by the BIOS which does not fit into the 256-byte data area at segment 0040h.
Extended File Control Block: A DOS File Control Block which has had an additional seven bytes prepended to permit control of file attributes (which are stored in the appendage).
Extended Memory: Memory beyond the one megabyte address which is available only on 80286 and higher machines. Except for a small portion (the High Memory Area) the extended memory is only accessible from protected mode.
Extended Memory Specification: A specification devised by Microsoft which allows multiple programs to share extended (above 1 megabyte) memory and noncontiguous memory above 640K.
FAQ: Frequently Asked Questions. A document containing basic questions and answers.
FAT file system: A file system based on a file allocation table, maintained by the operating system, to keep track of the status of various segments of disk space used for file storage.
FAT32: A 32-Bit enhancement of the File Allocation Table file system that supports large drives with improved disk space efficiency.
Fetch: The step in the instruction cycle where the instruction is located in memory and send to the control unit.
File: A collection of related data records treated as a unit, sometimes called a data set.
File Allocation Table (FAT): An area on the disk (floppy or logical drive) set aside to reference file locations on that disk. The table is a chain identifying where each part of a file is located. It acts similarly to a table of contents for a book.
File Control Block (FCB): A small block of memory temporarily assigned by a computer’s operating system to hold information about an opened file.
File Handle: A small positive integer used to identify the previously opened file on which a program wishes to perform an operation.
Floppy Diskette: A flexible, Mylar magnetic diskette commonly used with microcomputers on which data are magnetically stored.
Floppy Diskette Drive: The device used to transfer to and from a floppy diskette.
Flush: To force the copying of any data still stored in temporary buffers to its final destination.
Format: The arrangement of data on a medium.
Formatting: Preparing a storage medium (usually magnetic media such as a disk or tape) for storing data. Low-level or physical formatting writes all necessary housekeeping data to enable the storage device to read the media and may also initialize the storage units on the media to a known state. High-level or logical formatting writes data used by the operating system, such as allocation information and directories onto media, which has already been physically formatted. Formatting programs often perform both a low-level and a high-level format.
Gigabyte: One billion bytes. More accurately, 2 to 30th power or 1,073,741,824 bytes in decimal notation.
Hard Disk: A rigid metal platter coated with a magnetizable substance. Contrast with floppy drive.
Hard Disk Drive: the device used to transfer data to and from a hard disk.
Hardware tree: The hierarchical representation of all the buses and devices on a computer.
High Memory Area: The first 65520 bytes (64K less 16 bytes) of extended memory. This area is accessible from real mode on the 80286 and higher processors because these processors do not wrap addresses at one megabyte as the 8088 and 8086 do.
High Performance File System (HPFS): An OS/2 file system that allows long file names.
HiPack: A file and folder compression format.
IDE: Integrated Drive Electronics, The most common interfaces popular today for PC hard disks.
Interrupt: An asynchronous operating condition that disrupts normal execution and transfers control to an interrupt handler. Interrupts are usually initiated by I/O devices requiring service from the processor.
Interrupt request (IRQ): A method by which a device can request to be serviced by the device’s software driver. The system board uses a programmable interrupt controller to monitor the priority of the requests from all devices.
Kernel: One of three core components in Windows 98. It provides base operating system functionality, including file I/O services, virtual memory management, and task scheduling.
List of Lists: An internal DOS table of lists and other tables through which most DOS-internal data structures may be reached.
Logical block addressing (LBA): A method of accessing hard disk drives based on the extensions of INT 13.
Magnetic Disk: A flat circular plate with a magnetic surface on which data can be stored by selective magnetization of portions of the curved surface.
Magnetic Drum: A circular plate with a magnetic surface on which data can be stored by selective magnetization of portions of the curved surface.
Magnetic Storage: Utilizing the magnetic properties of materials to store data on such devices and media as disks, tapes, and chips.
Magnetic Tape: A plastic tape with a magnetic surface on which data can be stored by selective magnetization of portions of the surface.
Mass Storage: Secondary storage devices with extra large storage capacities such as magnetic or optical disks.
Megabyte: One million bytes. More accurately, 2 to the 20th power or 1,048,576 in decimal notation.
Memory: Same as storage.
Memory Control Block: The data structure containing the length and owner (among other things) of a portion of the memory managed by DOS.
Non-Volatile RAM: Memory which can be modified like normal RAM but does not lose its contents when the system's power is turned off. This memory may be powered by a battery when the system power if off, or it may be a type of memory which does not need electricity to maintain its contents, such as EEPROM or bubble memory.
Nonvolatile Storage: A storage medium that retain is contents in he absence of power.
Operating System (OS): A set of programs that controls and supervises a computer system’s hardware and provides services o programmers and users.
Optical Disk: A secondary storage medium using laser technology to read tiny spots on a plastic disk. The disks are currently capable of storing billions of characters of information.
Option ROM: Optional read-only memory found on PC bus expansion cards. This ROM usually contains additional firmware required to properly boot the peripheral connected to the expansion card, for instance, a hard drive. Also referred to as an expansion ROM.
Park: To move a hard disk's read/write heads to a position in which it is safe to turn off the power and transport the disk drive. Many drives also lock the heads into position when they are parked, providing additional protection from sudden movement.
Password: A unique string of characters that must be provided before logon or access to a resource or service is authorized.
Password caching: Automatically storing a password in a password list (PWL) file so that whenever the user logs on again, the logon password unlocks the PWL file and the resource passwords it contains.
PC Card: A trademark of PCMCIA. A removable device that is designed to be plugged into a PC Card slot and used as a memory-related peripheral.
Power-On Self-Test: A brief examination of the system's functionality performed each time the system is turned on.
Primary Storage Section: Also known as internal storage and main memory, this section of the processor holds program instructions, input data, intermediate results, and the output information produced during processing.
Program Segment Prefix: The Program Segment Prefix is a 256-byte data area prepended to a program when it is loaded. It contains the command line that the program was invoked with, and a variety of housekeeping information for DOS.
RAM (Random Access Memory): (1) A storage device structured so that the time required to retrieve data is not significantly affected by the physical location of the data. (2) The primary storage section of personal computer.
Read/Write Head: The electromechanical component of the tape drive that performs the actual writing or reading on or from magnetic tape.
Real-Time Clock: A battery-powered clock, which continues to maintain its time even while the system is powered down. On PCs, the real-time clock contains a small amount of battery-powered memory (set CMOS RAM).
Refresh: The process of periodically rewriting the contents of a DRAM memory chip to keep it from fading. The term "refresh" is also commonly applied to redrawing the image on a CRT's phosphors.
Registry: The database repository for information about a computer’s configuration. The registry supersedes use of separate INI files for all system components and applications that know how to store values in the registry.
Registry Checker: A system maintenance program that finds and fixes registry problems and backs up the registry.
Registry Editor: An application that is used to view and edit entries in the registry.
Registry key: An identifier for a record or group of records in the registry.
Root directory: A specific area set aside to store boot files and directories.
ROM (Read-Only Memory): A memory for program storage which may not be changed by the program as it runs.
Route table: A table that is used to determine where a computer routes packets.
Scatter/Gather: A technique in which the contiguous data of a disk sector or sectors is transferred to or from multiple non-contiguous areas of memory. When reading into multiple areas of memory, this is called a scatter-read and the opposing operation is called gather-write.SCSI (Small Computer Systems Interface): A system-independent expansion bus typically used to connect hard disks, tape drives, and CD-ROMs to a computer. A host adapter connects the SCSI bus to the computer's own bus.
Searching: The process of locating and retrieving data stored in a file.
Secondary Storage: Storage that supplements the primary storage of a computer. Synonymous with Auxiliary storage.
Sector: The smallest addressable unit of data on a disk. Under MS-DOS, this is normally 512 bytes.
Sequential Access: A method of storing and accessing data in a row, or one after another. To access a record, all preceding records must be read first.
Set-up script: A text file that contains predefined settings for all the options specified during setup.
Soft Copy: A form of volatile output, usually a screen display.
Sort: To arrange data into a predetermined sequence.
SRAM (Static Random Access Memory): RAM which typically consists of one flip-flop per bit of memory. Unlike DRAMs, static RAM retains its contents as long as power is applied. Because there is no need to refresh the contents of memory addresses which are read, SRAM is faster than DRAM, but it is more expensive and typically is available in much smaller sizes than DRAM because each bit occupies more space on the chip.
State Memory: Data internal to a module that survives unchanged from invocation o invocation of that module.
Storage: Pertaining to a device into which data can be entered, in which it can be held, and from which it can be retrieved at a later time.
System File Table: System File Table is a DOS-internal data structure used to maintain the state of an open file for the DOS 2+ handle functions, just as an FCB maintains the state for DOS 1.x functions.
System Maintenance: The ongoing process of monitoring and evaluating a system.
Swap file: A hidden file on the hard drive that Windows uses to hold parts of programs and data files that do not fit in memory.
Testing: The fiendish and relentless process of executing all or part of a system with the intent of causing it to exhibit a defect.
Time bomb: A method of sabotaging a computer programs so that it will destroy itself after a predetermined time or action occurs.
Track: One of multiple concentric circular rings of data on a single data-bearing surface of a disk. Tracks at the same location on different surfaces form a cylinder.
TSR (Terminate and Stay Resident): A program which remains in memory after terminating in order to provide services to other programs or the user. The name comes from the name of the DOS function call used to remain in memory after termination.
UDF: Universal Disk Format, A file system developed by the Optical Storage Technology Association for storage of data on optical media.
UltraPack: A file and folder compression format that offers better compression than standard or HiPack compression.
Undo: A feature in application software that allows the user to cancel the action of the previous instruction.
Upper Memory Block: noncontiguous section of allocatable memory located between the 640K and 1024K addresses.
VCACHE: A 32-bit, protected-mode cache driver, which replaces the 16-bit, real-mode SMART Drive disk cache software.
Virtual Control Program Interface: A simple API for protected-mode programs to allocate memory and switch into or out of protected mode.
Virtual memory: Memory that appears to an application to be larger and more uniform than it is.
Virus: A program which attaches itself to other programs for the purpose of duplicating itself. Viruses often (but not always) contain harmful code, which is triggered by some event, after a certain number of reproductions, or on a specific date.
Volatile Memory: Memory (such as electronic semiconductor memory) that loses its contents in the event of a power interruption.
WORM (Write Once, Read Many): A storage medium, which may be written exactly once, but may not be altered once data is stored.
Worm: A program, which duplicates itself, typically across networks. In contrast to a virus, a worm does not attach itself to other programs, but can reproduce itself independently.
Write-behind caching: Temporarily storing data in memory before it is written on disk for permanent storage.
Write-Through: One of two main types of caches, the write-through cache immediately writes any new information to the medium it is caching, so that the cache never contains information which is not already present on the cached device.
XBDA: see Extended BIOS Data Area.
XMS: see Extended Memory Specification.
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