Jim Mohr's SCO Companion
Copyright 1996-1998 by James Mohr. All rights reserved. Used by permission of
Be sure to visit Jim's great Linux Tutorial web site at http://www.linux-tutorial.info/
contains a list of commonly used terms and expressions. In many cases
I wrote something in bold in the definition as a flag that this is
something important. The fact that a word or phrase is in bold, does
not necessarily mean it has it's own glossary entry. I just felt you
needed to pay attention to it.
mode — Changing file permissions using the 3-digit
octal numbers, instead of the letters.
pathname — A pathname for a file or directory
beginning at the root directory and including the leading slash (/).
keys — Keystrokes that select menu options of
functions without explicitely pressing the button or selecting the
control. See security
— The environment that a user accesses in order to
log into the system.
partition — The partition from which the hardware
will try to boot.
window — The window currently accepting input.
- Automatic Call Unit. The term used in UUCP files to refer to a
— 1) A memory location. 2) The user and machine name
used to send an electronic mail message.
— Adapter Description File. File provided with MCA
devices on the options disk which contains configuration
information for that device
— The person who manages your computer system or
— Acer Fast Filesystem. Older filesystem used on SCO
system that increases preformance by grouping files into 16K
— Adavanced Hardware Supplement. A supplement
provided by SCO that includes drivers to newer hardware
— A name that is more commonly used or is easier to
remember that represents something else. If your shell supports
aliases, an alias can be a a command that represents another command.
In mail, this is an address that represents another address.
tracks - Tracks that are used to store data contained in bad
— Hypertext links. A anchor or hypertext link is a
link from one document to another
- American National Standards Institute.
- Occurs when adding more memory makes machine go slower. Sometimes,
the CPU cannot cache eveything, so it caches nothing, thereby making
the whole system run slower.
- Advanced Power Management.
— A computer program that performs a particular
task, such as word processing or managing a database.
Process to determine which device has access to a particular
resource, such as the sytem bus.
— See command argument.
— address resolution protocol.
— American Standard Code for Information Interchange.
This is only the 128 character set and does not contain non-English
command set. See Hayes command set
— See permissions.
— Ability to access a particular system function.
answer — setting your modem to automatically pick up when
an incoming call is received.
— The process that automatically mounts an NFS
filesystem when a file or directory under the mount point is
— A programming language on many UNIX systems.
process — A process that does not require
interaction with the user to run. While a background process runs,
the user can continue using other programs or commands.
— Slash that goes from the upper left to lower right
(\). Also called a descening slash. Used to "escape”
the special meaning of certain characters.
- Similar to an apostrophe except that it slants from upper right to
lower left. Used to "hold” the output of a command.
— A copy of files, directories, or filesystems,
normally used as protection against accidental deletion, but also
used as to maintain a copy of a object in a known state. Also the
process of making a backup.
track — A track on the hard disk that con no longer
be read from or written to properly. Bad tracks are listed in a bad
track table which points to good alias tracks.
channel — A mail channel through which all mail
addressed to unrecognized machines is sent. The machine to which the
mail is sent is a smart host.
channel — A mail channel through which all mail
addressed to unrecognized machines is sent. The machine to which the
mail is sent is a smart host.
— Referes to the maximum I/O throughput of a system.
Although this normally refers to communications channels such as
ethernet or serial lines, it is often used to refer to any system.
address — The setting used to access expansion cards.
— The file name component of a path. This can also refer to
the "primary” portion of a file name. For example, the
base name of the file program.c
could be thought of as program.
This is also the name of the command used to extract the basename.
Compare this to directory name or dirname.
One change in the electrical state of a signal.
rate - The number of electrical state changes per second.
— The buffer flushing daemon, which writes the
contents of dirty buffers from the buffer cache to disk.
— The numerical system of counting with only two digits: 0
and 1. Also called base
— The process of joining two components. Networking
programs are often bound to a port, or key presses in the X-Windows
systems are bound to a specific function.
— Basis Input/Output Services. Special chip set on the the
computer that is used to access the hardware. SCO mainly uses this
during boot-up and shutdown, although operating systems such as DOS
use it as the primary means of accessing the hardware. The term BIOS
is used for both the chip itself and the routines contained within
— A binary digit. Either a 0 or a 1.
— A representation such as a picture or table that
is stored as a series of 0's and 1's. Each character represents a
single dot in the image or a particular value in the table.
device — A hardware device that is accessed with buffering
within the operating system. Although such device can be read by an
application a character at a time, input and out is buffered within
the system's buffer cache. Compare this to a character
I/O — I/O where the process is forced to
wait until the operation is complete. Also known as synchronous I/O.
— The process by which the computer is powered on and goes
through the necessary stops to load and start the operating system.
This also refers to the program in the root directory that loads and
starts the operating system.
device — The device (usually a floppy or a hard disk) from
which the system is booted.
— The string passed to the boot program that it uses
to detemine what operating system to load and execute as well as how
to do so.
— When demand for a particular resource is beyond
the capacity of that resource or beyond the ability of the operating
sustem to provide that resource.
- A computer or other netwokr device used to connect two
networks. Bridges are often considered to connect similiar systems,
such as two Ethernet networks. Compare this to a gateway.
— Uninitialized data. An acronym for block started
by symbol. (Often called blank static storage.)
— Boot-Time Loadable Driver. A device driver that
is added to the operating system as it is booted. Unless such a
driver is added permanently to the system or added the next time the
system boots, it will not be available again.
— An area of computer memory or the hardware that is
used to temporarily store information.
cache — The system buffer that stores the most-recently
accessed blocks. Note this is only used when accessing block devices.
— A set of lines (such as wires or leads) used to transfer
data or control information. See also expansion bus.
arbitration — The process of deciding which device has
control of the bus.
mastering devices. Also bus masters. Devices which are
capable of taking control of the ystem bus.
— Eight bits.
memory — Also called just cache. High-speed
memory usually placed between a CPU and main memory. Cache memory
holds recently accessed memory as it is more likely that this memory
will be accessed again. See also level-one (L1) cache and
level-two (L2) cache.
return — The keyboard key usually labeled
<Return> or <Enter>. When your are typing at the command
line, sending a carriage return indicates to the system that you are
ready for the system to process the comman. The term comes from
typewritters where pressing the carriage return actually returned the
carraige of the typewriter to it's starting position.
— Signal that is used as a reference point from which
frequency changes are measures. These frequency changes are the
— Comite Consultatif International Telegraphique et
— A read-only optical storage media that uses the same
technology as music CDs.
connector — Official name of the printer side if a parallel
— Color graphics adapter. Old, old video card.
— Term used to describe the connection between different
layers in a network.
— The program used to phsyical transfer mail.
device — A hardware device that is accessed with no
buffering within the operating system. Although such device can be
read by an applicationin blocks, input and out is not buffered
within the system's buffer cache. Compare this to a
— Character MOSAIC.
script — Set of Expect-Reply pairs used by UUCP to
log into a remote system.
— The process by which specific filesystems have
data and control structures written regularly to the disk.
— A value that is calculated based on the bites within a
file. Some checksums are dependent on the order of the bytes within a
file, whereas other are not. Two files with identical content
must have the same checksum.
process — The process created when one process (the
parent) calls the fork() system call.
— 1) A group of printers, normally all of the same
type that behave from the users' perspective as a single
printer. 2) Description giving to computer networks depending on what
portion of thier IP address is the network and which is the
— The state of a data object when it has not had its
contents altered. "Dirty” buffers or pages can be marked
clean when the data is written to disk. Filesystems are marked as
clean when the control structures are written to the disk.
— A process or machine that is using a particular
resource that is provided by a server. In X-Windows, a client
is usually an application that creates a display on the screen. In a
network, a client is a machine that accesses a remote filesystem or
model — A model in which some components act as
servers, providing resources or services and other components are
clients that use those resources or services.
tick — The term used for an interrupt received at
regular intervals from the programmable interrupt timer or clock.
Clock ticks are signals to the kernel to allow it to initiate actions
that need to be taken at regular intervals.
— Complementary Metal-Oxide Semiconductor.
Technically any chip that uses the CMOS technology, but more commonly
used to refer to a special chip that retains the basic confioguration
information about your machine.
— Common Object File Format. One of the executable
program formats used by SCO.
— Certificate of License and Authenticity.
port — Common term for a serial port. Although this is
actually the DOS term, it is used often. the term comes from
— A set of words or characters that is interpreted
by the operating system as a request for action on the part of the
alias — An alternative name for a command. See also
argument — Subsequent information passed to a command. This
normal refers to information (such as the name of a file) that needs
to be acted upon. Normally arguments that change a commands bheavior
are called flags or options.
flags — See command options.
line — A place on your screen where you input
commands. The command line is usually indicated by a prompt.
Also refers to the string of characters that form your command.
line interpreter — The program that accepts your command
line and reacts to it. See also shell.
options — Arguments passed to a command that change its
— The process of taking the source code for a
program and converting it into machine readable instructions.
disk — A logical disk composed of parts of multiple
— When two devices, processes, etc. request a system
resource at the same time. For example, when two devices want to use
the bus at the same time.
— The set of data, including the CPU register values
and uarea that describe the state of a process.
switch — The process by which the system goes
through to change from one process being the current/active one to
character — A character that has an ASCII value
less than 32. These are often created by pressing the <Ctrl>
key and another key. Programs can also generate control characters.
These get their name from the fact that they are often used to
control certian function of an applications.
key — The key marked CTRL on most keyboards.
This is used to modify the value sent by another key that is pressed
at the same time.
— Central Processing Unit . The primary chip
or processor in a computer. The CPU is what reads and executes the
machines instructions and makes the computer go.
privilege level — The level of access a process has while
running. This essentially determines what memory and hardware can be
— An abnormal shutdown of the computer. Often this exhibits
itself as the system "freezing,” but it can also be that
the system reboots itself or panics.
cable — A serial cable in which the transmit pin on one end
of the cable goes to the receive pin on the other end and visa-versa.
current working directory — The directory that
the system accesses when no paths are given. The current directory
can also be specified as . or ./ depending on the context. This
directory is taken as the starting point for all relative pathnames.
— The symbolic indicator of where input is being
taken. This is usually in the form of a box, underline, I-shaped
character or other shape that make or may not be blinking.
— The set of all tracks on a harddisk that are
equadistant from the center of the disk.
— 1) Digital to Analog Converter. Chip (usually) on
a video card that converts the digital signals from the operating
system to analog signals that the monitor uses. 2) Discrentionary
— A process that performs a service for the system.
Normally, daemon process are in the background and are waiting
for something to occur that they must react to.
— Digital Audio Tape. A form of backup (tape) media.
mode — The mode a modem is in when it is transfering data.
— Data Communication Equipment.
— The numerical system of counting with ten
digits:0123456789. Also called base
— To convert date from an encoded format into a form
that readable by the approapriate process. (human, program, etc.) See
— The standard configuration or values for a
program, field or any other aspect of the system
boot string — The bootstring that is executed when you
press return at the Boot:. This is the defined in /etc/default/boot
by the entry defbootstr.
process — A process that has made the exit() system call.
This process does not use any system resources (including memory)
except that it takes up a slot in the process table.
— Pointers to specific memory locations that are
used by the kernel. These are stored in descriptor tables.
— Any peripheral hardware attached to the system.
These are accessed by device drivers through device nodes.
driver — A set of routines internal to the kernel
that performs I/O with a peripheral device. Although it is normal a
user's process that wishes to access that peripheral device, it
is the kernel that is actually doing the work.
nodes — Special files that are the entry points into the
device drivers. Also referred to as device files.
enormus — The technical term for making mistakes
while typing. This translates as "fat fingers.”
connector - Deutsche Industrie Norm connector. Small 9-pin
connector used to attach peripheral device such as mice and
— Dual In-line Pin Package. Usually refers to memory chips
that are connected via two rows of parallel pins.
— A file in a particular format that is read by the
system as a an inode and filename pair. The files contained within a
directory can also be other directories.
name — Also referred to simply as directory. This
is the name of the directory path used to access a file. The
directory component can be access with the dirname command.
— The state of a buffer or memory page that has had
its contents changed.
access control. Security of a system where access is determined
by the system administrator (at his or her discrention) and not
forced by the system.
mirroring — The process by which the entire contents of a
hard disk are duplicated on another disk.
pieces — The components of a virtual disk.
striping — The process by which parts of a logical or
virtual disk is spread across multiple physical disks. This
differs from a concatenated disk in that disks are not seen as
being read in sequence, but rather in parallel. The portion of the
virtual disk that resides on a on physical disk is referred to a
— Also called a floppy disk or floppy.
A thin, flexible data disk within a protective jacket. Data is stored
on the floppy and accessed through the media access hole.
— A portion of a hard disk partition that may or
may not contain a file system. The start location of each
division is stored at the begining of the partition in the division
table or divvy table.
— Data Link Provider Interface. A standard by which
networking protocols access networking hardware.
— Direct Memory Access. The means by which devices can
access memory directly without the intervention of the CPU. DMA
is controlled by the DMA controller.
— Domain Name System. Also called Domain Name Service and
Domain Name Server. The system by which information about a computer
network is stored on specific machines rather than spread out on
every machine. Information is obtained by making a query which
is then resolved by the domain name server or name
— A set of machines on a network that are controled by a
single administrative authority. The domain name is the
name by which the domain is known.
— A sort of operating system. Although the term
refers to several different operating systems, it is most commonly
associated with Microsoft's DOS, MS-DOS.
file — A UNIX file that has a period (dot) as it's
first character. With the exception of the root users, dot file are
normally not visible. Because they are only visible with specific
options to certian commands, they are often equated to DOS "hidden
notation — The notation used to indicate IP addresses as
— (") Used to partially remove the special
significance os certain characters. Characters such as the $,
single-quotes(‘) and back-ticks (`) retain their
— Dynamic Random Access Memory. Must be refreshed regularly
with electric signals. Compare this to SRAM.
— The machine readable version of a device driver. The
Driver.o files are linked into to the kernel to provide access
to the devices.
— Data Terminal Equipment
— Desk Top File System. SCO's compression
— An inode from a DTFS.
In-Line Pin Package. See DIPP
device — The device that the system will write to (if it
can) when the system panics.
Link Libraries (DLLs) — Libraries of functions that are
linked into the program as needed (at run-time) and not when
the program is compiled.
— Extended Acer Fast Filesystem.
— Error Checking and Correcting.
interrupts — Interrupts that are activated by the rising
edge of the signal. That is when the signal is making the transition
from low to high. Compare this to level-triggered interrupts
— Extended Functionality Supplement. Supplement supplied by
SCO that provide functionality not included in the standard product.
Compare this to SLS.
— Enhanced Graphics Adapter. Another old, old video
— Enhanced Integrated Digital Electronics. A newer
device interface. Most often used in in hard disks and can overcome
size limitations of IDE drives.
— Extended Instruction Pointer. The register
containg the memory location that the CPU is currently executing.
— Extended Industry Standard Architecture. Ehanced
version of the ISA. Developed by a consortium of companies abd
providing advantages over ISA.
— Executable and Linking Format. A new executable
program format used by SCO.
— The process by which one data format is enclosed inside
of another. This technique is used in networking to pass data between
the various layers.
— Converting data from one form to another. The newer form
is generally more easily handled than the original. For example,
8-bit data converted to 7-bit data to send via mail is encoded.
— Encode something so that it is no longer readable by
humans or other processes.
password — The user's password that is stored in
encoded form in the /etc/shadow and
the Protected Password Database.
— See user.
— The settings and values that control the way you
work on the system. These include the shell you use, your home and
current directories, and your user and groups IDs. There are also a
set of variables called environment variables that contain
many of these settings and values.
variable — Variables that modify the behavior
of your login shell as well as other programs.
message — A message indicating a problem. This can
be something as simple as when input incorrect syntax to a command or
something more significant like a needed file is missing. Usually the
messages indicates the nature of the problem.
character — Decimal 27, octal 033 and hexidecimal 1b.
Character used in many cases as a flag to indicating the following
sequence of characters has special meaning.
key — The key which is marked ESC on most keyboards.
This key is used to generate and escape character that is often used
to remove the special significance of certian other characters.
sequences — A sequence of characters preceeded by an escape
character. This usually changes the behavior of something. For
example, escape sequences to printers might turn on bold printing.
characters — The process by which you remove the specially
significance of characters. This is often accomplished by preceeding
the special character by a back-slash.
— Enhanced Small Device Interface. An older hard disk
— A local area network standard developed by the Xerox
— An occurence on the system. For the kernel this
might be that a device is ready to provide requested data. For
X-Windows this can be keystrokes, mouse movement, or resizing
— An unexpected event.
handlers — Special functions within the kernel that are
used to deal with expection.
file — A file containing a program or a set of
commands. In order to be executable, these files must also have the
execute permission bit set.
— The value returned by a process as it is completing.
memory — In DOS-based computers a means of getting around
the 640K base memory problem. With this technique, blocks of 64k are
shuffled in and out of "accessable" memory.
bus — The bus in a computer into which expansion
cards are inserted.
card — A card inserted into the expansion bus that
expands the functionality of the system such as a hard disk
controller or a serial port.
— The process by which a filesystem or directory is
made available to be remotely mounted.
memory — Addition memory above 1Mb. This memory is not
switched in as with expanded memory but is treated as a
single, linear unit.
minor numbers — A technique used to allow the system to
have more devices that are premitted by the single byte available for
minor numbers. Normally extended minor numbers are only used for hard
— An exception that occurs before the instruction is
executed (e.g., page faults).
separator — A special character used to delimit fields
within a file or input.
— A named collection of information stored on a hard
disk, floppy or other media. Although a file is normally considered
to contain data or executable instructions, hardware in UNIX is
accessed through files. These do not have any size and therefore
contain no data, their mere existance is what contains the
creation mask — See umask.
descriptor — A number associated with an open file.
This is used to refer to file during I/O operations.
permissions — The access permissions on a specific file.
table — A table internal to the kernel that maintains the
the relationship between the file descriptors and the physical
file on the hard disk.
— A hierarchical organization of directories and
level cache — The cache
contained with the CPU.
— See command options.
control — The process by which data transfer is regulated
so that it does not arrive too quickly for the receiving process.
— A process is said to be in the foreground when it is
interacting with the user.
— The process and system call by which new processes are
— The process by which a disk is prepared for use.
slash — Slash that goes from the upper right to
lower left (/). Also called an ascending slash. Used as the
— Fully Qualified Domain Name. Machine name
containing both the host name and the domain name. This name is used
to uniquely indentify a computer.
— When parts of a file are spread out across
different parts of a hard disk. Although the term is also used to
refer to memory, accessing memory from different locations has no
effect on the process. However, when reading a file, being forced to
go to different locations, the physical movement of the hard disk
components slow down the access.
— A linked list of unallocated (free) data structures.
— A file transfer program that allows you to copy
files to and from a remote computer in a network.
path — See absolute pathname.
— Gateways are often considered as connecting dissimilar
systems such as one network running TPC/IP and the other running
— See gigabyte.
— Global Descriptor Table.
— Group ID.
— 230 bytes. Often thought of (erroneously) as
one billion bytes.
— A set of users. These users are listed under a
group name within the /etc/group
file. The group name is associated with a GROUP ID (GID). Each
file on the system has a group associated with it. This is indicated
by the GID of the file.
— Graphical User Interface. A graphic oriented interface
such as X-Windows.
link — A file with a different full path name but the same
inode number. Compare this to a symbolic link.
flow control — Controlling the flow of data across a
serial cable by using line signals rather than control characters.
bus — A bus to which the access is determined by special
hardware and not software.
command set — Standard set of modem commands.
— Information included at the beginning (head) of
transmitted data. A header will indentify the information being sent
and may contain other information. For example, a mail header would
contain the recipient whereas an IP header contains the source and
destination IP addresses.
— The numerical system of counting with sixteen digits:
023456789ABCDEF. Also called base
ratio — The ratio of times that information was available
to the number of times it was requested. For example, if data is
requested from cache memory and is available, this is a cache
hit. If the data is not available, this is a cache miss..
directory — The directory defined by your $HOME
environment variable. This is normally the same directory you end up
in after you log into the system.
— The number of connections that need to be made to reach a
destination. For example, if you want to go from machine A to machine
B, but first need to go to machine C, this is two hops (A->C then
— Any computer. Normally used when the computer is
on a network.
adapter — An expansion card that serves as the interface
between the system's expansion bus and a SCSI
bus. This is often (erroneously) called a SCSI controller.
— The system name or machine name.
— High-Performance Pipe System. System
used in SCO OpenServer where pipes are stored in memory and not on
the hard disk.
— The kernel daemon that manages filesystem control
— High-Throughput File System. One of SCO's new
— HyperText Markup Language. Text formatting
language used in WWW documents.
— HyperText Transfer Protocol. Protocol used to transfer
— Abbreviation for input/output. This refers to the
transfer of data to and from peripheral devices.
— Internet Control Message Protocol.
— A graphical representation of something.
— Integrated Drive Electronics. Common hard disk interface.
— Interrupt Descriptor Table. Table containing pointers to
the interrupt handling routines.
— The process "spawner" that is created at system
— Index or Information Node. This is a structure
containg the basic information about a file such as owner, type,
access permissions and pointers to the actual data on the disk.
Inodes are stored in the per filesystem inode table and are
referenced through inode numbers. See also file.
logging — Process by
which pending filesystem transactions are logged. If the system goes
down unexpectedly, such transactions can be completed or ignored
depending on the state they were in.
— A signal from a hardware device indicating the
devices wants "attention.” This can include things like
an indicator that requested data is available or an error has
handler — Special routines within the kernel that handle
Service Routine. See interrupt handler.
— Internet Protocol. Standard by which packets of
information are sent to the appropriate location within a network.
address — Unique address within a network that uses the
— Installation Query Manager. SCO's installation program.
— interrupt vector. The hardware setting indicating what
line a device will generate an interrupt.
— Industry Standard Architecture.
— Intergrated Services Digital Network.
— Internation Standards Organization.
— Interrupt Service Routine. See interrupt handler.
— International Telecommunications Union.
or Kb - See Kilobyte.
— The primary part of the operating system. This
manages all system functions such as memory, task scheduling, how
devices are accessed, etc.
mode. See system mode
parameter — A value defined that controls the
configuration of the kernel.
— 210 bytes.
— Local Area Network.
— Local descriptor table.
(L1) cache — Cache memory within the CPU.
interrupts — Interrupts that are indicated by them
eltrical signal being level, but at the state opposite from what it
(L2) cache — Cache memory external to, but directly
accessed by the CPU.
call — A call to a library function. Library
functions are collections of system calls.
link — 1) hard link.2) soft link.
3) The processes of combining all the drivers and other kernel
components to create an new copy of the kernel.
count — The number of file names that point to a
particular set of data.
— The name used to refer the collection of tools and files
used to create a copy of the kernel.
– Link Layer Interface. Older method used on SCO systems to
interface network protocols with network device drivers.
— The set of values that indicate your location such as
language, keyboard type, etc.
— The special name name given to the machine you are
currently working on.
principle — Principle that the computer instruction which
are executed are generally within the same area of memory (spatial
locality) and that the same instructions are likely to be
executed again (temporal locality).
— See transaction intent logging.
block addressing — The means by which blocks on the hard
disk are accessed based on a logical address and not the absolute
address on the hard disk. The logical address is what is presented to
the operating system by the hard disk controller.
— The process of gaining access to the system. Here you
enter you login name (logname) and password.
group — The GID that you are assinged by
— The name you use to gain access to the system.
— The process of disconnecting yourself from the system.
— Logical Unit Number. Number used to identify a device
controller by a single SCSI host adapter. Compare this to SCSI
address — Media Access Control address. The unique
identifier given to a network interface card. (NIC).
number — A number at the beginning of a file used to
indicate what type of file it is.
mode. See system maintenance mode.
number — A number indicating which device driver
should be used to access a particular device. See also minor
— A reference page containing useful information about a
— A series of bits that "cover up'' existing
settings. For example, the umask masks out file permissions
and the netmask masks out network addresss.
interrupts — Interrupts that can be "ignored."
block — The first block of your hard disk (or floppy)
containing infrormation necessary to find the active partition and
boot your operating system.
— See megabyte.
— Master Boot Record. See masterboot block.
— Micro-Channel Architecture. A computer bus architecture
developed by IBM. It provides many advantages over the ISA
— 220 bytes
— A special character that is replaced by character
strings by the shell..
— Multipurpose Internet Mail Extensions. A
standard for mail exchange, which supports graphical, audio, video,
and other binary data.
number — A number serving as a flag to a device driver.
See also major number.
— See disk mirroring.
— Multichannel Memorandum Distribution Facility.
One of the two SCO MTAs.
drives — Magneto-Optical drives. A storage media that uses
both magetical properties and lasers to store data.
control port — A serial port that reacts to the carrier
– Modulator/Demodulator. An electronic device attached to
your computer that converts digital signal from the computer to
analog signals (modulation) to be transmitted across telephone cable.
When receving the analog signals, a modem converts them back into
digital signals (demodulation).
— The process by which filesystem are made
point — The directory through which the mounted filesystem
table — The table containing all of the mounted
— A pointing device used to move a pointer on the
— Mail Transfer Agent. The collection of programs
used to transfer mail from one system to another. SCO systems provide
two MTAs: MMDF and sendmail.
— Maximum Transmission Unit. Maximum size of a transmitted
piece of data.
— Mail User Agent. The program that you
use to interface into the mail system, including reading and
— The process by which a computer system is able to
maintain multiple programs (tasks) in memory and to switch fast
enough to appear as if all programs are being run simultaneously.
— The process by which a computer system is able to
maintain multiple programs (tasks) in memory and to ensure that they
do not interfer with each other. Normally each task is associated
with a specific user.
mode — The run state of the system in which access is
allowed on terminals other than the system console.
system — A computer system with more than one CPU.
— One of the 12 console "terminals."
— Motif window manager. A program that controls window
configuration and behavior. and creates window frames.
server — A program running on a network that
provides a centralized database of information on the names and IP
Addresses of machines on that network.
cache — A data structure within the kernel
that stores the most-recently accessed translations of pathnames to
— A binary mask used to mask out the network portion on an
— A group of computers that are linked together.
— Network Filesystem. The set of programs and the protocol
used to make filesystems and directories avaialble across a network.
value — A weighting factor that is used to calculate
a processes priority.
— Network Information System. System by which files and
user information can be automatically spread across a network.
— non-maskable interrupt. An interrupt that cannot be
— The numerical system of counting with eight
digits:01234567. Also called base
— A common abbreviation for SCO's Open Desktop.
— Intel Object Module Format. One of the executable program
formats used by SCO.
system — A group of programs and functions
that provide basic functionality on a computer. This software that
manages access to a system's hardware and other resources.
disk — A disk provided with MCA devices that contains an
ADF for that device.
— Operating System Direct. A support service provide by
owner — 1. The user who created a file or
directory. 2. The user that started a process.
— A collection of related programs that perform a common
function. Packages are parts of products.
— A unit of data being sent across a serial line or
— A 4KB block of memory. The primary unit of memory.
directory — A structure in memory that the kernel uses to
access page tables.
fault — A hardware event that occurs when a process
tries to access a virtual address that is not in physical memory.
table — A structure in memory that the kernel uses to
— The process the kernel goes through when an unexpected
event occurs that it cannot deal with.
— The process by which data is sent bytes at a time.
Compare this to serial.
directory — The directory which contains the directory you
are refering to. For example. if you refer to the /etc/default
directory, then the parent directory is /etc.
If your current directory is /usr/jimmo,
then the parent directory is /usr.
process — The process that executed a fork() system
call to create a new, child process.
— An error detection mechanisms in which the number of bits
is counted and an extra bit is added to make the total number of bits
set even for even parity or odd for odd paritiy.
bit — The extra bit used for parity.
— A section of a hard disk, which can be the entire hard
disk. The starting location and size of each partition is stored in a
— A string of characters that you use to confirm
your identity when you log in. An encrypted version of this is stored
in the TCB and /etc/shadow, which
then compared to your input when attempting to login.
— 1. The set of directories that are needed to reach
a specific file. Also referred to as the pathname.
list of directories through which the shell searches to find the
commands you type.
PCI — 1)
Peripheral Component Interconnect. One of the newer bus types. 2)
PC-Interface. Product provided by SCO that allows PCs access
to an SCO system.
— Printer Control Langauge.
— Another computer at the same "level" as
yours. You can provide services to them and they to you. Computers in
this situation use a peer-to-peer model. Compare this to a
— The settings associated with each file or
directory that determine who can access the file and directory and
what types of access are permitted. Also called properties or
memory — RAM.
— Programmable Interrupt Controller. Chip on the
motherboard that manages hardware interrupts.
— Process ID. Unique identifier for a process. This is
simply the process' slot number in the process table.
— A way of joining commands on the command line
where the the output of the first command provides the input for the
next. The term also refers to the symbol used to create the pipe: |.
— Panning Motif Window Manager.
— The process by which a device driver queries a devices
for a response rather than waiting for the device to generate an
— Power-On Self-Test. Self-test that the computer goes
through when you first turn it on.
— Parent Process ID.
— Point-to-Point Protocol. Networking protocol used across
data — Variables and other structures within a program
that already have their value set before the program is run.
— What occurs when a process that was running on a
CPU is replaced by a process with a higher priority.
queue — A queue (waiting line) in which print
requests are stored awaiting to be sent to the printer.
spooler — The term used to described the files and programs
used to manage files to be printed.
class — Multiple printers that are treated as one
destination in order to spread the load more equally.
interface scripts — Shell scripts that actually sent the
file to the printer.
— The value that the scheduler calculates to
determine which process should next run on the CPU. This is
calculated from its nice value and its recent CPU usage.
. See sub-system authorizations.
— An instance of a program that is being execution.
Each process has a unique PID, which is that process's entry
in the kernel's process table.
table — A data structure within the kernel that
stores information about all the current processes.
— One or more characters or symbols that identify
that the system is ready to accept a command.
mode — A CPU mode in which mechanisms are implemented to
allow or deny access to particular areas of memory. In other words,
memory is protected.
subsystems — Certain actions within the system that are
controlled by system privilidges.
— A set of rules and procedures used to establish
and maintain communication. That can be between hardware or software.
stack — A set or protocols which appears to be
stacked as one protocol hands off information to another.
suite — A collection of related protocols.
— Also called a pseudo-tty. A device driver
that allows one process to communicate with another as if it were a
— A list. A waiting line.
— The mechanism that is used to control the
substitution of special characters. See single-quotes,
double-quotes and back-ticks.
Redundant Array of Inexpensive Disks. Combining multiple disks to
improve reliablility or performance.
— Random access or main memory.
device — See character device.
— The process by which one of the three base file
descriptors (stdin, stout and stderr) reference something other than
— An area of memory grouped by function. For
example, text, data and stack.
descriptor — A descriptor pointing to a region.
table — A structure within the kernel pointing to the
currently active regions.
expression — A notation for matching sequences of
characters without having to specific all possible combinations.
Regular expressions are composed of literal characters as well as
path — A pathname that shows a path in
relation to the current working directory.
— The process by which a new kernel is generated.
host — A computer in a network other than the
one that you originally logged in to.
— request for comments. A specific document that relates to
networking standards and activity.
— Read Only Memory.
root — 1. The top directory of a UNIX filesystem,
represented as a slash (/). Also called the root directory. 2.
the login name of the super user.
filesystem — The file system onto which all the other
filesystem are mounted and which usually contains most of the system
— A path to a particular computer. The set of other
computers need to reach that destiantion.
— A device used to redirect network connections to the
— Remote Procedure Call. A system call that is
executed on a remote machine.
flow control — A form of flow control using the two signals
Request-To-Send and Clear-To-Send.
— Also called run-state. An abstract term that is
used to determine which process should be run or started.
— The process by which request for data from a hard disk
that are spread out across the disk (scattered) are ordered into a
more efficient list (gather) to minimize the total access time.
— The system swapper daemon. This deamon determines
which process get to run.
— The Santa Cruz Operation.
— Small Computer System Interface. An expansion bus
that is controlled by a host adapter and supports several
different device types.
level cache — See L1 Cache.
— The mechanisms and policies used to pevent unauthorized
access to system resources.
— The smallest administrative unit on a hard disk. It
contains 512 bytes of data.
— Stream Editor. A stream/file manipulation program. The
term is also used to refer to the language used to program the sed
— See Region.
— The process by which data is sent one bit at a time.
Compare this to parallel.
ports — A device port that supports serial communication.
— Software Enhancement Service. A service provided by SCO
giving you upgrades and updates at a reduced costs as well as the
Software Support Library.
data region — A data region that can be accessed by
libraries — Sets of common library routines that are not
part of a program, but exist as separate files on the disk and can be
accessed by different processes.
— The program that controls the user interaction to
the operating system.
escape — A command or character you type from
inside an interactive program to escape to the shell.
script — A text file containing written UNIX
commands, shell built-in commands and shell programming syntax. Shell
scripts must be made executable by setting the execute permission
variable — A variable associated with a shell
— A flag sent to a process indicating a certain event has
— Single In-Line Memory Module.
— (') Quotes that remove the special significance of all
other characters. See double-quotes and back-ticks.
mode. See system maintenance mode
— Serial Line Internet Protocol. A networking procotol used
on serial lines.
— Support Level Supplement. Supplement provided by SCO free
of charge that usually include patch or updates.
host — A computer that has more complete information
about the mail network. This includes both information on users and
— Simple Mail Transfer Protocol. A mail transfer protocol
used over TCP/IP and the Internet.
— A old method of transfering data between two machines
— Simple Network Management Protocol. A protocol used to
manager information within a network.
— Start of Authority. A record with DNS used to
determine which machine is the authoritative soruce of information.
link. See symbolic link.
Enhancement Service. See SES.
flow control — Flow control using the XON and XOFF
characters. Compare this to hardware flow control.
interrupts — Interrupts generated by software and not
— The name of the machine with SCO's bulletin board.
— A file within the linkkit containing device driver
— Software Priority Level.
— Although refering to any process that routes requests
to a file or memory for later processing, this term in normally used
for the print spooler.
— Static RAM.
— Software Support Library. A CD containing SCO's
Information Tools, SLSs and EFSs.
— Software Storage Object. The primary way of storing files
and packages in OpenServer.
— A list of temporary data used by a process when
making function calls.
region — The area of a process' virtual memory that
contains it's stack.
error — The place where a process usually writes
error messages, by default the screen. Also called stderr.
input — The place where a process usually takes its
input, by default, the keyboard. Also called stdin.
output — The place where a process usually writes
its output, by default, the screen. Also called stdout.
bit — The bit indicating the begining of a byte being
bit(s) — The bit(s) indicating the end of a byte being
— A mechanism for implementing a layered interface
between applications and a device driver. Most often used to
implement network protocol stacks and X-Windows.
width — The number of physical drives in a striped disk.
See disk striping.
array — See disk striping.
— A shell that was started by another process.
authorizations — Access to specific, but varied, parts of
the system, such as printing, backups, and memory.
— A directory residing within another directory.
— A name that describes a smaller orgnaization unit
within a domain. An example would be the SCO subdomain within the COM
— A logical portion of a network.
— SET USER ID. The premissions bit that enables the process
to run under a different user ID.
— An area at the beginning of a filessytem containing
information about that filesystem.
— The user who has the special privileges needed to
administer and maintain the system. The super user logs in as root.
— Super VGA. A newer video standard.
device — An area on the disk reserved for swapping
out portions of processes, if the physical memory available becomes
— The action taken by the operating system (the
swapper daemon) when the system is short of physical memory. The
changable portion (data) of a process os moved from physical memory
to the swap device.
link — A file that contains the path to another file
or directory. Since this is just a path, symbolic links can cross
mount points. Depending on the length of the path specified and the
filesystem, symbolic links can also be stored within a file's inode.
mode — Changing file permissions using keyletters to
specify the set of permissions to change and how to change them.
Compare this to absolute mode.
call — A low-level system function. Compare this to a
maintenance mode — The run-level in which access is
only allowed through the system console. Used for maintenance, hence
mode — The state of a CPU where the kernel needs to
ensure that it has privileged access to data and physical devices.
Also called kernel mode.
— See terabyte.
— Trusted Computing Base. The file used to control and
manage C2 security on an SCO system.
— Transmission Control Protocol. A reliable protocol that
is used transmit data from one process to another across a network.
— 240 bytes.
— Video display unit with a keyboard and a monitor.
resistors — Resistors at the end of a thin-wire network
connect or SCSI bus that absorbs the signals and prevents them
from bouncing back, potentially interfering with other signals.
— The executable machine portion of a porgram. That
is, the part of a program containing the instructions that a CPU can
interpret and act on.
file — A file containing text.
region — Also called text segment.
— When the system spends all of its time swapping
and not performing any real work.
— The amount of work that a part of the system can
process in a specified time. This can be anything from the number of
bytes send to the number of jobs completed.
slice — The maximum amount of time a process
can run without being preempted.
— Translation Lookaside Buffer. Buffer within the CPU that
contains pointers to pages.
— To switch between any two conditions. For example,
to toggle from OFF to ON.
— The set of sectors on a hard disk at the same distance
from the center and on the same surface.
intent logging — A new feature in OpenServer
and one of the functions of the htepi_daemon. This is the process by
which the the intention to change filesystem control data is written
to a log file on disk.
layer — The layer of a network protocol stack responsible
for getting the data from one machine to another.
— An exception that is processes immedaitely after
executing the instruction that generates the exception.
— Task State Segment. Contains the contents of all
registers when a process is context switched out.
— The category that describes whether the file is a
regular file, a directory, or other type of file.
— The area of a process (user area) that contrains the
private data about the process that only the kernel may
access. Also called ublock.
— Universal Asynchronous Receiver-Transmitter.
— See uarea.
— User Datagram Protocol. An unreliable protocol that is
used transmit data from one process to another across a network
— User ID.
— A mask that controls the permissions assigned to
new files as they are create.
— An operating system originally developed at Bell
Laboratories. The version developed by SCO is the topic of this book.
— Uninterrupted Power Supply.
— Uniform Resource Locator. A "network extension"
to the standard filename concept. This allows access to files and
directories on remote machines, to which you may not have a constant
connection, such as NFS. URLs can also point to resources on the
local machine and provide a means of transporting the base files
without having to change paths.
user account — 1) The enviroment under
which a user gains access to the system. This includes the logname,
shell, home directory, etc. 2) The records and other
information a UNIX system keeps for each user on the system.
equivalence — The process by which accounts on two system
are considered equal and authentication is not longer required for
certain network operations.
mode — The state of a CPU when it is
executing the code for a user program that is accessing its own data
name — See logname.
— Any command that performs more than just a simply
function. An example would be fdisk
as you can use it to create, delete and make partitions active.
— Unix-to-Unix Copy. A set of programs and protocols used
to transfile files across serial lines, as well as perform remote
execute of commands.
— An object known to a proces that stores a
particular value. Shell variables are known to a particular shell
process and enviroment variables (generally) known to all of a
particular user's processes.
- Virtual Disk Manager.
number — The number associated with a particular
version of a file.
— The ability to store multiple copies of the "same"
file on the system.
— Video Electronics Standards Association.
— Video Graphics Array.
— The system name for the page stealing daemon.
address — An address that exists within a process'
virtual memory space.
disk — A disk composed of pieces of several physical
memory — A method of being able to access more
memory than is physically available on your system. This combines
physical RAM with the swap space as well taking advantage of
the fact that the entire program is not accessed at once and does not
need to all be in memory.
— Video Electronics Standards Association Local Bus.
— Windows Application Binary Interface.
channel — The addresss of an event on which a particular
process is waiting.
— see wait channel.
connected host — A host that is connected to many machines
— A space, tab or carriage return.
— Any character (such as ?
or *) that is substituted with another character or a group of
characters. See also metacharacter.
policy — How cache memory writes its contents to main
— The write policy when cache memory is written to
main memory at regular intervals.
— The write policy when cache memory is written to
main memory only when it has been changed
— The write policy when cache memory is written to
at the same time as main memory.
— World Wide Web. A collection of machines on the Internet
that contain documents. These documents contain hypertext
links to other documents which may of may not be on the same machine.
— See X-Windows Systemn
client — A process that communicates with an
X server to request that it display information on a screen or to
receive input events from the keyboard or a pointing device such as a
server — The software that controls the
screen, keyboard and pointing device under X.
Window System — A windowing system based on
the client-server model.
flow control — Flow controlling using the XON (Ctrl-Q) and
XOFF(Ctrl-S) character. Also called software flow control.
— Zero-Insertion-Force. A special socket with a lever that
locks the chip (normally the CPU) with no force required. Hence the
process — An entry in the process table that
corresponds to a process that no longer exists. This is used to hold
the exitcode of that process.
Copyright 1996-1998 by James Mohr. All rights reserved. Used by permission of
Be sure to visit Jim's great Linux Tutorial web site at http://www.linux-tutorial.info/