Glossary

absolute mode --
A method of changing file permissions using 3-digit octal numbers. For example, to add group write permission on a file called report using absolute mode, type chmod 664 report. Note that you must be root or the owner of the file to change permissions on that file. You can also change permissions using symbolic mode.

absolute pathname --
A pathname for a file or directory that begins at the root directory. Every absolute pathname begins with a slash character (/), which stands for the root directory. See also pathname and relative pathname.

application --
A computer program that performs a particular task. Word processing, spreadsheet, and database programs are all applications. See also Applications list.

Application folder --
A sublist on the main Applications list, which usually includes a list of related application programs. An Application folder can contain applications and other application folders. See also Applications list.

Applications list --
The list of available applications and application folders that is displayed on the main SCO Shell screen. See also application and Application folder.

archive --
To place a file or group of files in a form convenient for storage on backup media such as floppy disks or tape. Normally, you archive backup files or files that are important but not often used. Such files can be copied to and from backup media using the Archive option on the File menu. See also backup.

argument --
A word you type on the command line that is separated by a space from the command itself. A command can have more than one argument. Arguments tell a command how to you want it to work. For example, lf -a; the -a option tells the lf file listing program that you want it to show all files. These types of arguments are also known as options or flags. Arguments can also tell a command what you want it to work on: for example, lf -a /tmp/spell.out tells lf to list the file /tmp/spell.out if it exists.

ASCII --
The American Standard Code for Information Interchange is a standard way of representing characters on many computer systems. The term ``ASCII file'' is often used as a synonym for ``plain text file,'' that is, a file without any special formatting, which can be viewed using UNIX system utilities such as cat(C), more(C), and vi(C).

attribute --
Attribute bits are set on a file to control which users have permission to read, write, or execute it. See permissions.

backup --
A copy of one or more files, directories, or filesystems that is stored apart from the original to safeguard against unplanned deletion. Used as a verb, it means to create a backup copy. The Archive option on the File menu allows you to copy files to backup media for safekeeping. See also archive.

Bourne shell --
A UNIX system shell, named after its author, Steven R. Bourne. To start a Bourne shell from the command line, type sh and press <Enter>.

buffer --
An area of computer memory used to store information temporarily before it is written out to a more permanent location, like a file.

C shell --
An alternative UNIX System V shell supplied with the SCO OpenServer system. This shell, written by William Joy at the University of California at Berkeley, is known for its interactive features, such as the ability to recall and modify previous command lines. The C shell shell programming language has a syntax like that of the C language, hence the name. C shell is the standard shell on older versions of the Berkeley UNIX operating system found at many universities. To start a C shell from the command line, type csh and press <Enter>.

command alias --
An alternative name for a command. When you type the alias, the command is substituted for the alias. Aliases are useful when you remember commands by names other than their UNIX system names; for example, DOS users may think of dir rather than ls when they want to list a directory. Aliases are also useful for creating commands that perform several UNIX system commands at once. See the Operating System User's Guide for more information.

command line --
The instructions you type next to the shell prompt. Command lines can contain commands, arguments, and filenames. You can enter more than one command on a command line by joining commands with a pipe (|), or by separating commands using the command separator (;). The shell executes your command line when you press <Enter>.

command separator --
The semicolon (;) serves as a command separator on the UNIX system. If you want to issue several commands on one line, separate the commands with semicolons before you press <Enter>. For example, type ls; pwd and press <Enter> to list files and then print the working directory. Commands are executed in sequence as separate processes.

current directory --
See current working directory.

current working directory --
The directory where you are currently located. Use the pwd(C) command (print working directory) to see your current working directory. The current working directory is taken as the starting point for all relative pathnames. This directory is symbolically referred to as ``.'' in directory listings.

device --
Peripheral hardware attached to the computer such as a printer, modem, disk or tape drive, terminal, and so on. Devices in the SCO OpenServer system are controlled by device drivers which are linked into the kernel.

directory --
Where the UNIX system stores files. Directories in the UNIX system are arranged in an upside-down tree hierarchy, with the root (/) directory at the top. All other directories branch out from the root directory. The UNIX system implements directories as normal files that store the names of the files within them.

environment --
The various settings that control the way you work on the UNIX system. These settings are specific to the shell you use and can be modified from the command line or by modifying shell control files. For example, the directories the shell searches to find a command you type are set in the variable PATH, which is part of your environment.

environment variable --
Special variables that modify your login shell behavior. Typical examples are PATH, which defines the directories in which the shell will search for files or commands, and PROMPT which determines the on-screen shell prompt message. See also variable.

error message --
A message informing you that the computer cannot perform the task you requested. The error message briefly describes the nature of the problem.

file --
The basic unit of information on a UNIX filesystem. Regular files are usually either text (ASCII) or executable programs. Other types of files exist on the UNIX system such as directories, which store information about the files within them; device files, which are used by the system to access a particular device; and FIFO (First In First Out) pipe files, which are used to transfer data between programs. The attributes of each file are stored in the file's inode. See also directory.

file descriptor --
A number associated with an open file; used to refer to the open file in I/O redirection operations.

full pathname --
See also absolute pathname.

group --
A set of users who are identified with a particular group ID number on the UNIX system. Typically, members of a group are coworkers in a department or on a project. Each file on the UNIX system also has a group associated with it; this group, along with the owner and the permissions controls who can access and modify that file. You can see the group of a file by listing the file with the l command. To find out your own group, use the id(C) command.

home directory --
The place in the filesystem where you can keep your personal files and subdirectories. When you log in, you are automatically placed in your home directory. Typically, this will be /u/loginname or /usr/loginname, where loginname is your login name. The shell's shorthand for the home directory is ``~''. See tilde expansion.

inode --
The internal representation of a file, showing disk layout, owner, type (see file), permissions, access and modification times, size and the number of links. Each inode has a unique decimal identifier.

kernel --
The central part of the UNIX operating system, which manages how memory is used, how tasks are scheduled, how devices are accessed, and how file information is stored and updated.

Korn shell --
Written by David Korn, it is compatible with the Bourne shell, but provides a much wider range of programming features. The Korn shell also offers improved versions of many of the C shell's interactive features. To start a Korn shell from the command line, type ksh and press <Enter>. See also Bourne shell and C shell.

link --
A filename that points to another file. Links let you access a single file from multiple directories without storing multiple copies of the file. If you make a change to the content of a linked file, the change is reflected in each of the links. All links point to an inode. See also symbolic link.

literal --
A literal character or string is one that represents itself, that is, that can be taken literally (as opposed to a pattern, that represents some other characters). For a metacharacter to regain its literal value (for example, for to mean an asterisk and not ``zero or more characters'') it must be ``quoted''. See quoting and wildcard.

log in --
The way you gain access to a UNIX system. To log in, you enter your login name and password and the computer verifies these against its user account records before allowing you access.

log out --
What you do after you have finished working on a UNIX system. You can log out by pressing <Ctrl>D, typing exit, or typing logout, depending on your shell.

login name --
The name through which you gain access to the operating system. When you are logging onto the computer, you must enter this login name, followed by a password.

login shell --
The shell that is automatically started for you when you log in. You can start to work in other shells, but your login shell will always exist until you log out.

macro --
A collection of instructions or keystrokes that may be invoked using a single name or keystroke combination, used to automate regular and complex tasks.

mail alias --
A single name used to send mail to several users at once. For example, many users have aliases set up for mailing to the entire company, single departments, or groups of individuals.

manual page --
An entry in a UNIX reference manual. These entries can be accessed online using the man(C) command. A letter in parentheses following a command or filename refers to the reference manual section where the command or file is documented. For example, the man(C) command is documented in section C, Commands, of the Operating System User's Reference. They are also called ``man pages.''

mask --
A series of bit settings that ``cover up'' existing settings, only allowing some settings to show through, while masking out others.

metacharacter --
A special character that is replaced by matching character strings when interpreted by the shell. Metacharacters, which define the form of a string, and literal characters, which match only themselves, make up regular expressions.

multitasking --
A system that can do several jobs at once.

multiuser --
A system that can be used by more than one person at the same time.

named buffer --
A buffer used to copy text between files in the vi(C) editor. vi clears unnamed buffers when it switches files, but the contents of named buffers are preserved.

online --
Accessible from your terminal screen.

operating system --
A group of programs that provide basic functionality on a computer. These programs operate your computer hardware in response to commands like copy and print, and form a set of functional building blocks upon which other programs depend. An operating system also manages computer resources such as peripheral devices like disk drives or printers attached to the computer and resolves resource conflicts, as when two programs want to use a disk drive at the same time.

owner --
1. The user who created a file or directory. Only the owner and root can change the permissions assigned to the file or directory.

2. One of the attributes of a file that, along with its group and permissions, determine who can access and modify that file. You can see the owner of a file by listing it with the l command. Use the chown(C) command to change the owner of a file.

password --
The string of characters you are prompted for after you type your login name when you are logging in. Your password is the key that lets you into the UNIX system; you should choose it wisely, keep it secret, and change it regularly. Use the passwd(C) command to change your password.

path --
The directory list through which your shell searches to find the commands you type. Your path is stored in the shell variable PATH.

pathname --
The name of a directory or a file, for example, /usr/spool/mail. Each component of a pathname, as separated by slashes, is a directory, except for the last component of a pathname, which can be either a directory or a file. A single word by itself, such as Tutorial, can be a pathname; this is a relative pathname for the file or directory Tutorial from the current working directory. A single slash, (/), is the pathname for the root directory. See also absolute pathname and relative pathname.

permissions --
The settings (also called properties or attributes) associated with each file or directory that determine who can access or modify the file and directory. Use the l command to list a file's permissions; use the chmod(C) (change mode) command to change a file's permissions.

pipe --
A way of joining commands on the command line so that the output of one command provides the input for the next. To use a pipe on the command line, join commands with the vertical bar symbol, (|). For example, to sort a file, eliminate duplicate lines, and print it, you could type sort file | uniq | lp.

print job --
A request you have made to the printer to print a file. Each print job has an ID number that you can see using the lpstat(C) command. You can cancel a print job by typing cancel and its job ID number, then pressing <Enter>.

process ID --
A number that uniquely identifies a running program on the UNIX system. This is also known as the PID.

prompt --
One or more characters or symbols that identify a line on which commands can be entered, as in a UNIX or DOS window. ``Prompt'' also refers to the text displayed when the computer displays a request for input or an instruction. The default prompt can be replaced by setting the PS1 environment variable.

quoting --
A mechanism that is used to control the substitution of special characters. Special characters enclosed in single quotes are not replaced by their meaning, but remain embedded in the text when the quotes are stripped off. Double quotes are used to prevent the expansion of all special characters except ``$'', ``\'' and ```''.

regular expression --
A notation for matching any sequence of characters. The notation is used to describe the form of a sequence of characters, rather than the characters themselves. Regular expressions consist of literal characters, which match only themselves, and metacharacters.

relative pathname --
A pathname that does not start with a slash (/); for example; Tutorial, Reports/September, or ../tmp. A relative pathname is searched for, starting from the current working directory and may use the notation ``..'' to indicate ``one directory up from the current working directory.'' See also absolute pathname and pathname.

root --
The top directory of a UNIX filesystem, represented as a slash (/). Also, the login name of the superuser, a user who has the widest form of computer privileges.

shell --
A program that controls how the user interacts with the operating system. Using such programs, you can write a shell script to automate work you do regularly. The shells available with the SCO OpenServer system include the Korn shell, the Bourne shell, and the C shell.

shell escape --
A command you type from within an interactive program to escape to the shell. In vi, you can type :!command to escape to the shell and execute command. When command has finished executing, you are returned to the editor. You can start a new shell this way with :!sh, for example. To exit this subshell and return to the editor, press <Ctrl>D or type exit.

shell programming language --
A programming language that is built into the shell. The Korn shell, the Bourne shell, and the C shell all have slightly different programming languages but all three shells offer basics such as variable creation, loops, and conditional tests.

shell script --
An executable text file written in a shell programming language. Scripts are made up of shell programming commands mixed with regular UNIX system commands. To run a shell script, you can change its permissions to make it an executable file, or you can use it as the argument to a shell command line (for example, sh script). The shell running the script will read it one line at a time and perform the requested commands.

shell variable --
A variable associated with a shell script.

standard error --
The usual place where a program writes its error messages. By default, this is the screen. Standard error can be redirected; to a file, for example. Also known as stderr.

standard input --
The usual place from which a program takes its input. By default, this is the keyboard. Standard input can be redirected; for example, you can use the less-than symbol (<) to instruct a program to take input from a file. Also known as stdin, the standard input is identified by the file descriptor 0.

standard output --
The usual place where a program writes its output. By default, this is the screen. Standard output can be redirected; for example, you can use a pipe symbol (|) to instruct a program to write its output into a pipe, which will then be read as input by the next program in the pipeline. Also known as stdout, the standard output is identified by the file descriptor 1.

subdirectory --
A directory that resides within another directory. Every directory except the root directory is a subdirectory.

superuser --
A user who has powerful special privileges needed to help administer and maintain the system. The superuser logs in as root. Someone with the superuser or root password can access and modify any file on the system.

symbolic link --
A new name that refers to a directory or file that already exists. Use this name to change to another directory without typing its full pathname. Unlike normal links, symbolic links can cross filesystems and link to directories. See also link.

symbolic mode --
A method of changing file permissions using keyletters to specify which set of permissions to change and how to change them. For example, to add group write permission on a file called report using symbolic mode, you could type chmod g+w report. Note that you must be the owner of a file or the superuser to change permissions on that file. You can also change permissions using absolute mode.

system administrator --
The person who looks after the day-to-day running of the computer and performs tasks such as setting up user accounts and making system backups.

terminal --
Video display unit with a keyboard, a monitor, and sometimes a mouse. They do not have any independent processing power themselves and they must be connected to a computer before they can do any useful work.

terminal type --
A name for the kind of terminal from which you are working. Typically, the terminal type is an abbreviation of the make and model of the terminal, such as wy60, which is the terminal type for a Wyse60. Your terminal type is stored in the variable TERM.

tilde expansion --
The ability of the shell to translate instances of the tilde character (~) into the pathname of the user's home directory.

trash directory --
A subdirectory of a user's home directory in which files are temporarily stored before being removed from the system permanently. The trash directory is represented on screen by the Trash icon. You can remove files by dropping them on the Trash icon.

umask --
A permissions mask that controls the permissions assigned to new files you create. You can set your umask from the command line or in one of your shell startup files.

user account --
The records a UNIX system keeps for each user on the system.

variable --
An object known to your shell that stores a particular value. The value of a variable can be changed either from inside a program or from the command line. Each shell variable controls a particular aspect of your working environment on the UNIX system. For example, the variable PS1 stores your primary prompt string.

wastebasket --
A directory where deleted files are temporarily stored. Once you delete a file, it remains in the wastebasket directory until you exit SCO Shell, at which point all files in the wastebasket are permanently deleted. You can recover files from the wastebasket (provided you have not exited SCO Shell) using the Wastebasket option on the File menu. See also trash directory.

wildcard --
A character (such as ``?'' or ``'') that is substituted with another character or a group of characters in text searches and similar operations. See also metacharacter.