118	
			#
		117
2     
DON’T SKIP!
Glossary
archived file
A file that has been archived using either LZEXE or PKLITE, file compression utilities.
boot
To start a computer. The first step is to load startup instructions from the boot ROM or boot sector of a disk.
BIOS
A read-only memory chip that contains the coded instructions for the operating system to start the computer. Always present in portable computers, 
	a BIOS (boot ROM) is not susceptible to infection (unlike the boot sector on a disk). However, it is harder to update.
boot sector
A portion of a disk that contains the coded instructions for the operating system to start the computer.
boot sector infections
Contamination of the boot sector by a virus. Particularly serious because information in the boot sector is loaded into memory first, before virus protection code can be executed. The only certain way to eliminate boot sector infections is to restart from a disk known to be uninfected, then clean up the infection.
clean startup diskette
A diskette known to be uninfected, that contains the coded instructions from which the computer can be started. See Chapter 2 for instructions on preparing one.
cold boot
To start a computer from power-off state.
compressed file
A file (usually with a .ZIP extension) that has been compressed using the PKZIP file compression utility.
conventional memory
Up to 640Kb of main memory in which DOS executes programs.
corrupted file
A file that has been damaged. About 10% to 20% of viral infections involve viruses that damage files beyond repair.
detection
Scanning memory and disks for telltale marks or changes indicating that a virus might be present.
disinfect
To eradicate a virus so that it can no longer spread or cause damage to a system.
exception list
List of files to which validation codes should not be added because they are immunized against viruses or contain self-modifying code. Scans /AV option uses the list to avoid adding codes to inappropriate files; VShields /CERTIFY option can use it to allow certain unvalidated files to be run.
executable (file)
A file containing coded instructions to be executed by the computer. Executable files include programs and overlays.
expanded memory
Memory above the DOS 640Kb limit of conventional memory that is accessed by memory paging. You need special software, conforming to an expanded memory specification, to take advantage of expanded memory.
extended memory
Linear memory above the DOS 640Kb limit of conventional memory. Often used for RAM disks and print spoolers.
false alarm
Detecting a virus when none is present. 
infected file
A file contaminated by a virus.
master boot record (MBR)
A portion of a hard disk that contains a partition table that divides the drive into chunks, some of which may be assigned to operating systems other than DOS.
memory
A storage medium where data or program code are kept temporarily while being used by the computer. DOS supports up to 640Kb of conventional memory. Beyond that limit may be accessed as expanded memory, extended memory, or an upper memory block (UMB).
memory infection
Contamination of memory by a virus. The only certain way to eliminate memory infections is to restart from a disk known to be uninfected, then clean up the source of infection.
modified file
A file that has changed after validation/recovery codes have been added.
overlay infection
Virus contamination of a file containing auxiliary program code that is loaded by the main program.
partition table
See master boot record.
polymorphic virus
A virus that attempts to evade detection by changing its internal structure or its encryption techniques.
program
Software that performs a defined function on a computer. See executable.
read operation
Any operation in which information is read from a disk. DOS commands that perform read operations include dir (directory listing), type (display contents of a file), and copy (copy files). See also write operation.
recovery codes
Information that Scan records about an executable file in order to recover if it is infected by a virus. See also validation codes.
self-modifying program
Software that deliberately changes its own program file, often to protect against viruses or illegal copying, and is therefore difficult to validate in conventional ways.
standard extensions
Filename extensions (suffixes) that signify executable files—.EXE, .COM, .SYS, .DLL, .BIN, and .OVL—which Scan checks by default.
system errors
Errors that can prevent Scan from completing its job successfully. System error conditions include disk format errors (such as unformatted disks), media errors (bad sectors), file system errors (unreadable files), network errors (unable to log in), file access errors (access permission denied), device access errors (printer out of paper), and report failures.
terminate-and-stay-resident (TSR)
A program, like VShield,  that remains active in memory while you run other programs.
turbo
A scanning option that is faster than normal but less comprehensive (because it checks a smaller portion of each file).
unknown virus
A virus not yet identified and listed in SCAN.DAT. VirusScan can detect unknown viruses by observing changes in files that could result from infection.
upper memory block (UMB)
Memory in the range 640–1024Kb, just above the DOS 640Kb limit of conventional memory.
validate
To check that a file is authentic and has not been altered. Most validation methods rely on computing a statistic based on all the data in the file, which is unlikely to remain constant if the file itself is changed.
validation codes
Information that Scan records about an executable file in order to detect subsequent infection by a virus. See also recovery codes.
virus
A software program that attaches itself to another program in computer memory or on a disk, and spreads from one program to another. Viruses may damage data, cause the computer to crash, display messages, or lie dormant.
warm boot
To restart (reset) a running computer, in DOS by pressing [Ctrl]+[Alt]+[Del].
write operation
Any operation in which information is recorded on a disk. Commands that perform write operations include those that save, move, and copy files. Most write operations are also read operations because the system verifies that the data have been written correctly. See also read operation.
write protection
A mechanism to protect files or disks from being changed. 
A 3.5" diskette may be write-protected by sliding its corner tab so that the square hole is open; a 5.25" diskette by covering its corner notch with a write-protect tab. A file may be write-protected by changing its system attributes.
Eric: This has to be edited. Some of these definitions repeat sections of the book. Some refer to Scan GUI options--is that OK? Others are so fluffy they may float away. /dk