glossary.html

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

</B>
<DD>Internet Control Message Protocol. Part of TCP/IP that provides network layer management and control.
<DT><B><TT>imake</TT>
</B>
<DD>C preprocessor interface to <TT>make</TT> utility.
<DT><B><TT>inheritance</TT>
</B>
<DD>A method of object-oriented software reuse in which new classes are developed based on existing ones by using the existing attributes and behavior and adding on to them. If the base object is automobiles (with attributes of engine and four wheels and tires; behavior of acceleration, turning, deceleration), a sports car would modify the attributes: engine might be larger or have more horsepower than the default, the four wheels might include alloy wheels and high-speed&#150;rated tires; the behavior would also be modified: faster acceleration, tighter turning radius, faster deceleration.
<DT><B><TT>inode</TT>
</B>
<DD>See <TT>i-node</TT>.
<DT><B><TT>int</TT>
</B>
<DD>Integer.
<DT><B><TT>Internet</TT>
</B>
<DD>A collection of different networks that provide the ability to move data between them. It is built on the TCP/IP communications protocol. Originally developed by DARPA, it was taken over by NSF, and has now been released from governmental control.
<DT><B><TT>Internet Service Provider</TT>
</B>
<DD>The people that connect you to the Internet.
<DT><B><TT>IRC</TT>
</B>
<DD>Internet relay chat. A server-based application that allows groups of people to communicate simultaneously through text-based conversations. IRC is similar to Citizen Band radio or the chat rooms on some bulletin boards. Some chats can be private (between invited people only) or public (where anyone can join in). IRC now also supports sound files as well as text; it can also be useful for file exchange.
<DT><B><TT>ISAM</TT>
</B>
<DD>Indexed Sequential Access Method. On UNIX and other systems, ISAM refers to a method for accessing data in a keyed or sequential way. The UNIX operating system does not directly support ISAM files; they are typically add-on products.
<DT><B><TT>ISO</TT>
</B>
<DD>International Standards Organization.
<DT><B><TT>ISP</TT>
</B>
<DD>See <TT>Internet Service Provider</TT>.
<DT><B><TT>ISV</TT>
</B>
<DD>Independent Software Vendor. Generic name for software vendors other than your hardware vendor.
<DT><B><TT>K&#38;R</TT>
</B>
<DD>Kernighan and Ritchie.
<DT><B><TT>kernel</TT>
</B>
<DD>The core of the operating system that handles tasks like memory allocation, device input and output, process allocation, security, and user access. UNIX tends to have a small kernel when compared to other operating systems.
<DT><B><TT>keys, control</TT>
</B>
<DD>These are keys that cause some function to be performed instead of displaying a character. These functions have names: The end-of-file key tells UNIX that there is no more input; it is usually Ctrl&#43;D.
<DT><B><TT>keys, special</TT>
</B>
<DD>See <TT>keys, control</TT>.
<DT><B><TT>Korn shell</TT>
</B>
<DD>A user interface for UNIX with extensive scripting (programming) support. Written by David G. Korn. The shell features command-line editing and will also accept scripts written for the Bourne shell.
<DT><B><TT>LAN</TT>
</B>
<DD>Local Area Network. A collection of networking hardware, software, desktop computers, servers, and hosts all connected together within a defined local area. A LAN could be an entire college campus.
<DT><B><TT>limits</TT>
</B>
<DD>See <TT>quota</TT>.
<DT><B><TT>link file</TT>
</B>
<DD>File used to implement a symbolic link producing an alias on one filesystem for a file on another. The file contains only the fully qualified filename of the original (linked-to) file.
<DT><B><TT>link, hard</TT>
</B>
<DD>Directory entry that provides an alias to another file within the same filesystem. Multiple entries appear in the directory (or other directories) for one physical file without replication of the contents.
<DT><B><TT>link, soft</TT>
</B>
<DD>See <TT>link, symbolic</TT>.
<DT><B><TT>link, symbolic</TT>
</B>
<DD>Directory entry that provides an alias to another file that can be in another filesystem. Multiple entries appear in the directory for one physical file without replication of the contents. Implemented through link files; see also <TT>link file</TT>.
<DT><B><TT>LISP</TT>
</B>
<DD>List Processing Language.
<DT><B><TT>login</TT>
</B>
<DD>The process with which a user gains access to a UNIX system. This can also refer to the user ID that is typed at the login prompt.
<DT><B><TT>lp</TT>
</B>
<DD>Line printer.
<DT><B><TT>lpc</TT>
</B>
<DD>Line printer control program.
<DT><B><TT>lpd</TT>
</B>
<DD>Line printer daemon.
<DT><B><TT>lpq</TT>
</B>
<DD>Printer spool queue examination program.
<DT><B><TT>lprm</TT>
</B>
<DD>Printer spool queue job removal program.
<DT><B><TT>ls</TT>
</B>
<DD>List directory(s) command.
<DT><B><TT>man page</TT>
</B>
<DD>Online reference tool under UNIX that contains the documentation for the system&#151;the actual pages from the printed manuals. It is stored in a searchable form for improved ability to locate information.
<DT><B><TT>manual page</TT>
</B>
<DD>See <TT>man page</TT>.
<DT><B><TT>memory, real</TT>
</B>
<DD>Theamount of storage that is being used within the system (silicon; it used to be magnetic cores).
<DT><B><TT>memory, virtual</TT>
</B>
<DD>Memory that exists but you cannot see. Secondary storage (disk) is used to allow the operating system to enable programs to use more memory than is physically available.
<BR>Part of a disk is used as a paging file and portions of programs and their data are moved between it and real memory. To the program, it is in real memory. The hardware and operating system performs translation between the memory address the program thinks it is using and where it is actually stored.
<DT><B><TT>metacharacter</TT>
</B>
<DD>A printing character that has special meaning to the shell or another command. It is converted into something else by the shell or command; the asterisk (<TT>*</TT>) is converted by the shell to a list of all files in the current directory.
<DT><B><TT>MIME</TT>
</B>
<DD>Multipurpose Internet Mail Extensions. A set of protocols or methods of attaching binary data (executable programs, images, sound files, and so on) or additional text to email messages.
<DT><B><TT>motd</TT>
</B>
<DD>Message of the day.
<DT><B><TT>MPTN</TT>
</B>
<DD>MultiProtocol Transport Network IBM networking protocol to connect mainframe to TCP/IP network.
<DT><B><TT>Mrm</TT>
</B>
<DD>Motif resource manager.
<DT><B><TT>mtu</TT>
</B>
<DD>Maximum transmission unit.
<DT><B><TT>mwm</TT>
</B>
<DD>Motif window manager.
<DT><B><TT>Netnews</TT>
</B>
<DD>This is a loosely controlled collection of discussion groups. A message (similar to an e-mail) is posted in a specific area, and then people can comment on it, publicly replying to the same place (posting a response) for others to see. A collection of messages along the same theme is referred to as a thread. Some of the groups are moderated, which means that nothing is posted without the approval of the owner. Most are not, and the title of the group is no guarantee that the discussion will be related. The official term for this is Usenet news.
<DT><B><TT>NFS</TT>
</B>
<DD>Network File System. Means of connecting disks that are mounted to a remote system to the local system as if they were physically connected.
<DT><B><TT>NIS</TT>
</B>
<DD>Network Information Service. A service that provides information necessary to all machines on a network, such as NFS support for hosts and clients, password verification, and so on.
<DT><B><TT>NNTP</TT>
</B>
<DD>Netnews Transport Protocol Used to transmit Netnews or Usenet messages over top of TCP/IP. See <TT>Netnews</TT> for more information on the messages transmitted.
<DT><B><TT>Null Statement</TT>
</B>
<DD>A program step that performs no operation but to hold space and fulfill syntactical requirements of the programming language. Also known as a <TT>NO-OP</TT> for no-operation performed.
<DT><B><TT>object</TT>
</B>
<DD>An object in the truest sense of the word is something that has physical properties, like automobiles, rubber balls, and clouds. These things have attributes and behavior. They can be abstracted into data (attribute) and code (behavior). Instead of just writing functions to work on data, they are encapsulated into a package that is known as an object.
<DT><B><TT>operator</TT>
</B>
<DD>Metacharacter that performs a function on values or variables. The plus sign (<TT>&#43;</TT>) is an operator that adds two integers.
<DT><B><TT>options</TT>
</B>
<DD>Program- or command-specific indicators that control behavior of that program. Sometimes called <TT>flags</TT>. The <TT>-a</TT> option to the <TT>ls</TT> command shows the files that begin with <TT>.</TT> (such as <TT>.profile</TT>, <TT>.kshrc</TT>, and so on). Without it, these files would not be shown, no matter what wildcards were used. These are used on the command line. See also <TT>parameters</TT>.
<DT><B><TT>OSF</TT>
</B>
<DD>Open Software Foundation.
<DT><B><TT>parameters</TT>
</B>
<DD>Data passed to a command or program through the command line. These can be options (see <TT>options</TT>) that control the command or arguments that the command works on. Some have special meaning based on their position on the command line.
<DT><B><TT>parent process</TT>
</B>
<DD>Process that controls another often referred to as the child process or subprocess. See also <TT>process</TT>.
<DT><B><TT>parent process identifier</TT>
</B>
<DD>Shown in the heading of the <TT>ps</TT> command as PPID. The process identifier of the parent process. See also <TT>parent process</TT>.
<DT><B><TT>parent shell</TT>
</B>
<DD>Shell (typically the login shell) that controls another, often referred to as the child shell or subshell. See also <TT>shell</TT>.
<DT><B><TT>password</TT>
</B>
<DD>The secure code that is used in combination with a user ID to gain access to a UNIX system.
<DT><B>pathname</B>
<DD>The means used to represent the location of a file in the directory structure. If you do not specify a pathname, it defaults to the current directory.
<DT><B><TT>pathname, absolute</TT>
</B>
<DD>The means used to represent the location of a file in a directory by specifying the exact location, including all directories in the chain including the root.
<DT><B><TT>pathname, relative</TT>
</B>
<DD>The means used to represent the location of a file in a directory other than the current by navigating up and down through other directories using the current directory as a base.
<DT><B><TT>PDP</TT>
</B>
<DD>Personal Data Processor Computers manufactured by Digital Equipment Corporation. UNIX was originally written for a PDP-7 and gained popularity on the PDP-11. The entire series were inexpensive minicomputers popular with educational institutions and small businesses.
<DT><B><TT>Perl</TT>
</B>
<DD>Programming language developed by Larry Wall. (Perl stands for &#147;Practical Extraction and Report Language&#148; or &#147;Pathologically Eclectic Rubbish Language&#148;; both are equally valid.) The language provides all of the capabilities of <TT>awk</TT> and <TT>sed</TT>, plus many of the features of the shells and C.
<DT><B><TT>permissions</TT>
</B>
<DD>When applied to files, they are the attributes that control access to a file. There are three levels of access: Owner (the file creator), Group (people belonging to a related group as determined by the system administrator), and Other (everyone else). The permissions are usually <TT>r</TT> for read, <TT>w</TT> for write, and <TT>x</TT> for execute. The execute permissions flag is also used to control who may search a directory.
<DT><B><TT>PGP</TT>
</B>
<DD>Pretty Good Privacy encryption system.
<DT><B><TT>pine</TT>
</B>
<DD>Interactive mail program.
<DT><B><TT>pipe</TT>
</B>
<DD>A method of sending the output of one program (redirecting) to become the input of another. The pipe character (<TT>|</TT>) tells the shell to perform the redirection.
<DT><B><TT>pipe file</TT>
</B>
<DD>See <TT>pipe, named</TT>.
<DT><B><TT>pipe, named</TT>
</B>
<DD>An expanded function of a regular pipe (redirecting the output of one program to become the input of another). Instead of connecting <TT>stdout</TT> to <TT>stdin</TT>, the output of one program is sent to the named pipe and another program reads data from the same file. This is implemented through a special file known as a pipe file or FIFO. The operating system ensures the proper sequencing of the data. Little or no data is actually stored in the pipe file; it just acts as a connection between the two.
<DT><B><TT>polymorphism</TT>
</B>
<DD>Allows code to be written in a general fashion to handle existing and future related classes. Properly developed, the same behavior can act differently depending on the derived object it acts on. With an automobile, the acceleration behavior might be different for a station wagon and a dragster, which are subclasses of the superclass automobile. The function would still be <TT>accelerate()</TT>, but the version would vary (this might sound confusing, but the compiler keeps track and figures it all out).
<DT><B><TT>POSIX</TT>
</B>
<DD>Portable Operating System Interface, UNIX. POSIX is the name for a family of open system standards based on UNIX. The name has been credited to Richard Stallman. The POSIX Shell and Utilities standard developed by IEEE Working Group 1003.2 (POSIX.2) concentrates on the command interpreter interface and utility programs.
<DT><B><TT>PostScript</TT>
</B>
<DD>Adobe Systems, Inc. printer language.
<DT><B><TT>PPP</TT>
</B>
<DD>Point-to-Point Protocol. Internet protocol over serial link (modem).
<DT><B><TT>pppd</TT>
</B>
<DD>Point-to-Point-Protocol daemon.
<DT><B><TT>printcap</TT>
</B>
<DD>Printer capability database.
<DT><B><TT>process</TT>
</B>
<DD>A discrete running program under UNIX. The user&#146;s interactive session is a process. A process can invoke (run) and control another program that is then referred to as a subprocess. Ultimately, everything a user does is a subprocess of the operating system.
<DT><B><TT>process identifier</TT>
</B>
<DD>Shown in the heading of the <TT>ps</TT> command as <TT>PID</TT>. The unique number assigned to every process running in the system.
<DT><B><TT>pwd</TT>
</B>
<DD>Print working directory command.
<DT><B><TT>quota</TT>
</B>
<DD>General description of a system-imposed limitation on a user or process. It can apply to disk space, memory usage, CPU usage, maximum number of open files, and many other resources.
<DT><B><TT>quoting</TT>
</B>
<DD>The use of single and double quotes to negate the normal command interpretation and concatenate all words and whitespace within the quotes as a single piece of text.