The Graham Utilities for OS/2 - Version 2

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Glossary

access mode
When a process creates or opens a file, it specifies the access and share modes of the file. The access mode specifies whether the file is for reading, writing or both.
and
A logical operation between two numbers.
0 AND 0 = 0
0 AND 1 = 0
1 AND 0 = 0
1 AND 1 = 0
See also OR, XOR.
archive
An archive is a special file which is managed by an archive program. A set of files is merged into a single file. As each file is added to the archive it may be compressed so that the size of the archive is smaller than the sum of all of its components. There are various methods of compression. Each having their own strengths and weaknesses. Some of the common archive formats are: ARC, ARJ, PAK, LZH, ZIP and ZOO.
archiver
A program which manages archive files.
batch file
A batch file is a text file which contains a sequence of commands to be executed. Batch files do not necessarily execute in sequential order. They may loop or branch either unconditionally or in response to the exit code from a program.
binary
A number system which uses a base of 2. The valid numbers are 0 or 1.
bit
BIT stands for Binary digIT. A bit is the smallest amount of information which a computer can process. It may have a value of either 0 or 1. Computers store information in groups of bits, these groups may be nibbles, bytes, words or double words.
BBS
Bulletin Board System. A BBS is a computer program which enables people with a MODEM to connect two computers and transfer information between them. This information may include files, electronic mail or both.
boot sector
A boot sector is the first sector (logical sector one) on a disk volume. It contains information about the disk and a small bootstrap program.
bootstrap
A bootstrap is a small program which is contained in your boot sector. This program may "boot" your computer by loading the operating system, or it may simply display the message which you see when you attempt to boot off a non system disk.
byte
A byte is a group of 8 bits. A signed byte contains values from -127 to 128.
cache
The use of memory to buffer data which has to be transferred to and from a device which is slower than system memory.
CBCS
Single Byte Character Set. This character encoding scheme uses 8 bits to define a single character. This provides us with 256 different characters.
checksum
A checksum is a number used to check the integrity of a file. There are numerous methods for calculating a checksum value.
cluster
A cluster is the minimum number of sectors which are allocated on a logical disk volume. A file consists of one or more clusters. The number of sectors in a cluster is always a power of two.
cmd file
An OS/2 batch file has a .CMD extension.
command interpreter
The command interpreter is a program which reads the keyboard and executes the commands which the user enters. It is only used in either windowed or full screen command prompt sessions. Typically the command interpreter is CMD.EXE
compression
The method of shrinking a series of bytes to smaller than the total number of bytes.
CPU
Central Processing Unit. The piece of hardware which controls the computer. It executes the programs which run on a computer. OS/2 runs on the Intel 80286, 80386, 80486 and Pentium series of microprocessor CPU's.
DBCS
Double Byte Character Set. This character encoding scheme uses 16 bits to define a single character. This provides us with 65,536 different characters. It is used for all of the Asian languages as well as the Arabic and Hebrew ones.
decimal
A number system which uses a base of 10. The valid numbers are 0 to 9.
directory
A named group of files in a file system.
directory tree
An outline of all directories in a file system.
DLL
A Dynamic Link Library is a special file which contains subroutines that are bound to an application program at runtime, not link time. This may save disk space by placing commonly used routines in a DLL, rather than placing copies of all of the routines in each individual program.
double word
A group of thirty two (32) bits. When used as a signed variable it has a range of values from -2,147,483,648 to 2,147,483,647 and 0 to 4,294,967,295 as an unsigned number.
dynamic hot fix
Some file systems, such as HPFS, support dynamic hot fixes. When a sector on a disk has a correctable error the data will be moved to a good sector on the disk and the problem area will be marked as bad. This process of transferring data from bad to good portions of the disk whilst the disk is in use, is known as dynamic hot fixing.
environment variables
Environment variables are a group of strings which are associated with each process. You can view the entire group of environment variables by entering the SET command at any command prompt.
errorlevel
This is a special statement in batch files which enable conditional jumping on the exit code returned from a program. They are used in conjunction with an IF statement in a batch file. The errorlevel statement acts as a "greater than" or "equal to" for the specified error level. For example: 
BE DAY
if errorlevel 3 goto Finish
if errorlevel 2 goto Second
:First
echo Today is the first day of the month
goto Finish
:Second
echo Today is the second day of the month
:Finish
exit code
When a program terminates, it returns an exit code which may be registered by the command interpreter as an errorlevel.
extended attributes
See appendix A for a complete description of extended attributes.
FAT
File Allocation Tables. A method which uses tables to define the clusters used by files and directories.
fidonet
A BBS network which started in the US in the mid eighties. It is run by individuals who fund the cost of running the BBS themselves. Currently, there are over twenty thousand fidonet BBS's world wide.
file attributes
Attributes attached to a file. The attributes may include:
Read Only
Indicating that the file may only be opened for reading.
Archive
Indicating that the contents of the file have changed and that it needs to be backed up.
System
Indicates that the file is part of the operating system.
Hidden
Indicates that the file should not be listed in normal directory listings.
file system
The part of the operating system which manages directories and files. It can translate file access calls into requests which the disk device drivers can use to transfer data to and from logical disks.
general protection fault
An error which occurs when a program executes an invalid instruction or uses an invalid memory address. OS/2 takes control and terminates the application when a GP fault occurs. It is also known as a TRAP D, referring to the interrupt number for the Intel series of processors which is called when a GP fault occurs.
hexadecimal
A number system which uses a base of 16. The valid digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F, representing the numbers zero to fifteen. Each hexadecimal number is represented by a group of four bits. It is used heavily in the computer world as it means an eight bit byte can be represented by two hexadecimal digits.
HPFS
High Performance File System. A special file system for OS/2 which uses caching and different allocation strategies to achieve significant performance increases over the FAT file system. HPFS also allows file names of up to 254 characters.
integer
A group of sixteen bits. It is a signed number and has a range of values from -32,768 to 32,767.
logical disk
Is represented by a letter and a colon. For example A:. It contains a boot sector, root directory and zero to many subdirectories. Multiple logical drives may span a single physical drive.
LSN
Logical Sector Number. This is the sector number of a sector from the beginning of a logical disk, as opposed to a physical disk.
Maximus BBS
A BBS system written by Scott Dudley. It is available for both the OS/2 and DOS operating systems.
MIME
Mulipurpose Internet Mail Extensions. A format for imbedding binary and others types of files in EMail messages.
multitasking
The process of sharing a processor among multiple processes so that they all appear to be running simultaneously.
MSB
Most Significant Bit, or the right most bit. It may be used as a sign bit to allow signed numbers.
nibble
A group of 4 bits. A nibble represents a single hexadecimal digit. As a number it ranges from 0 to 15 in decimal or 0 to F in hexadecimal.
number systems
Number systems are means which we use to represent numbers. People use the decimal number system, but computers use binary number system. The octal and hexadecimal number systems are directly related to the binary number system. They are all a power of two. The way in which they are used is still the same. For example the number 123 decimal is represented as: 
102    101   100
100    10    1
1*100  2*10  3*1
1      2     3
or 123 decimal. The same number in binary would be expressed as: 
27 +  26 + 25 + 24 + 23 + 22 + 21 + 20
128   64   32   16   8    4    2    1
0*128 1*64 1*32 1*16 1*8  0*4  1*2 1*1
0     1    1    1    1    0    1   1
or 01111011 binary. The same number in hexadecimal would be expressed as: 161 + 160 16 1 7*16 B*1 7 B or 7B hexadecimal.
octal
A number system which uses a base of 8. The valid digits are 0, 1, 2, 3, 4, 5, 6 and 7. Each octal number is represented by a group of three bits.
or
A logical operation between two numbers.
0 OR 0 = 0
0 OR 1 = 1
1 OR 0 = 1
1 OR 1 = 1
See also AND, XOR.
partition
A physical fixed size allocation of disk space. Logical disks reside in partitions.
physical disk
A physical or real disk attached to your system. A single physical disk may be partitioned into multiple logical disks.
preemptive multitasking
The ability of the CPU to share itself among multiple processes without their cooperation.
Presentation Manager
The graphical user interface for OS/2.
priority
A number associated with each thread or process. Processes with a higher priority receive more CPU than threads with a lower priority.
process
An instance of an executing program. A process may own, files, pipes, semaphores, memory as well as other system resources.
root directory
The first directory on a disk within which all files and other subdirectories exist.
sector
The smallest area on a disk which can be either read or written by a disk drive. It is usually 512 bytes, but it may be 128, 256, 1024 or 2048.
semaphore
An interprocess communication mechanism which has only two states. It is typically used to signal ownership of a resource.
session
See process.
share mode
When a process creates or opens a file, it specifies the access and share modes of the file. The share mode defines how other processes can access the file. Other processes may have, read and write, read only, write only or no access to the file.
signed number
A signed number is a number where the MSB is used as the sign bit. This allows the number to hold negative numbers.
slack
The difference between the actual file size and the amount of space allocated to the file by the file system.
stack fault
A CPU exception which occurs when a program uses all of its assigned stack space. It is also known as a TRAP E.
subdirectory
A group of files or directories which are located under the root directory.
system semaphore
A system semaphore is a special form of semaphore that has the form: \SEM\PATH\FILENAME.EXT Where the PATH and .EXT portions are optional.
task
See process.
thread
The point of execution within a process. A process has at least one thread.
timer tick
A hardware interrupt which occurs periodically to enable OS/2 to monitor the system.
timeslice
The amount of time that OS/2 allocates to a thread before having to preempt it.
time slicing
See preemptive multitasking.
UNIX
An operating system originally designed by AT&T.
unsigned number
An unsigned number is a number which has no sign bit. Its value ranges from zero to the maximum value allowed by the size of the number.
volume label
A special file name which may be used to label a logical disk. It has a maximum of eleven characters.
write-through
A cache mode. Data is not held in cache memory, it is transferred directly to the device.
word
A group of sixteen bits. It is an unsigned number and has a range of values from 0 to 65,535.
xor
Exclusive OR. A logical operation between two numbers.
0 XOR 0 = 0
0 XOR 1 = 1
1 XOR 0 = 1
1 XOR 1 = 0
See also AND, OR.