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        !            22: .rs
        !            23: .SP .5i
        !            24: .TL
        !            25: GLOSSARY
        !            26: .SP 2
        !            27: .LP
        !            28: This glossary covers major terms that have special meaning for the
        !            29: UNIX system.
        !            30: It excludes ordinary terms of art such as
        !            31: `ASCII', `compiler', `address space', or `byte'.
        !            32: It also excludes most terms peculiar to a single part of UNIX, e.g.
        !            33: `diversion' (\fItroff\fR), `enumeration' (C),
        !            34: or `pattern space' (\fIsed\fR).
        !            35: .SP 1.3v
        !            36: .nr PS 9
        !            37: .nr VS 10
        !            38: .2C
        !            39: .H absolute pathname\ 
        !            40: same as
        !            41: .C full pathname.
        !            42: .nr PD 1u
        !            43: .H access time\ 
        !            44: the most recent
        !            45: .C time
        !            46: at which the contents of a 
        !            47: .C file
        !            48: [2] were read or
        !            49: .C executed
        !            50: [2]; cf.\&
        !            51: .C modification time.
        !            52: .H alarm\ 
        !            53: a
        !            54: .C signal
        !            55: scheduled by the clock.
        !            56: .H a.out\ 
        !            57: the default name of a freshly compiled
        !            58: .C object file,
        !            59: pronounced `A-dot-out';
        !            60: historically 
        !            61: .CW a.out
        !            62: signified assembler output.
        !            63: .H archive\ 
        !            64: 1.\&
        !            65: a collection of data gathered from several
        !            66: .C files
        !            67: into one file.
        !            68: 2.\&
        !            69: especially, such a collection gathered by
        !            70: .I ar (1)
        !            71: for use as a
        !            72: .C library.
        !            73: .H argument\ 
        !            74: 1.\&
        !            75: a
        !            76: string made available to a
        !            77: .C process
        !            78: upon
        !            79: .C executing
        !            80: a
        !            81: .C file.
        !            82: 2.\&
        !            83: a string in a
        !            84: .C command,
        !            85: which the
        !            86: .C shell
        !            87: [1] will pass to the command program
        !            88: as an argument [1].
        !            89: .H ASCII file\ 
        !            90: same as
        !            91: .C text file.
        !            92: .H automatic\ 
        !            93: persistent only during the invocation of a procedure, said of
        !            94: data belonging to a
        !            95: .C process;
        !            96: automatic data occupies the
        !            97: .C stack segment;
        !            98: cf.\&
        !            99: .C static.
        !           100: .H background\ 
        !           101: running independently of a
        !           102: terminal, said of a
        !           103: .C process;
        !           104: converse of
        !           105: .C foreground.
        !           106: .H basename\ 
        !           107: 1.\&
        !           108: the last component of a
        !           109: .C pathname;
        !           110: the basename of
        !           111: .CW /bin/proc
        !           112: is
        !           113: .CW proc .
        !           114: 2.\&
        !           115: occasionally a basename [1] with conventional
        !           116: suffixes removed; see
        !           117: .I basename (1).
        !           118: .H blit\ 
        !           119: vernacular name for a prototype
        !           120: Teletype 5620 terminal; cf.\&
        !           121: .C jerq.
        !           122: .H block\ 
        !           123: 1. \&
        !           124: the basic unit of
        !           125: .C buffering
        !           126: [1]
        !           127: in a
        !           128: .C file system
        !           129: [3], 1024 or 4096 bytes in this system.
        !           130: 2. \&
        !           131: a unit in which memory usage is reported, usually 1024 bytes,
        !           132: but 512 bytes in imported code such as
        !           133: .I cpio (1).
        !           134: .H block device\ 
        !           135: a
        !           136: .C device
        !           137: that may contain a
        !           138: .C file system
        !           139: [3],
        !           140: typically a permanent storage device such as a tape or
        !           141: disk drive; the unit of data transfer is one
        !           142: .C block;
        !           143: cf.\&
        !           144: .C character device.
        !           145: .H boot\ 
        !           146: to start the operating system, so called because the
        !           147: .C kernel
        !           148: must bootstrap itself from secondary store into an empty machine.
        !           149: No
        !           150: .C login
        !           151: [3]
        !           152: or
        !           153: .C process
        !           154: persists across a boot.
        !           155: .H boot block\ 
        !           156: the first block of a
        !           157: .C file system
        !           158: [1],
        !           159: which is reserved for a 
        !           160: .C booting 
        !           161: program.
        !           162: .H break\ 
        !           163: 1.\&
        !           164: an out-of-band signal on an asynchronous data line arising from
        !           165: the `break' or `interrupt' key on a terminal;
        !           166: before
        !           167: .C logging in
        !           168: a break causes a change in baud rate;
        !           169: thereafter it is interpreted as an
        !           170: .C interrupt.
        !           171: 2.\&
        !           172: a control statement in C or
        !           173: .I sh (1).
        !           174: 3.\&
        !           175: the
        !           176: .C program break.
        !           177: 4.\&
        !           178: in
        !           179: .I troff (1),
        !           180: a point in running text where a new line must begin.
        !           181: .H BSD\ 
        !           182: see
        !           183: .C UNIX.
        !           184: .H bss segment\ 
        !           185: see
        !           186: .C segment.
        !           187: .H buffer\ 
        !           188: 1.\&
        !           189: a staging area for input-output where arbitrary-length
        !           190: transactions are collected into convenient units for system operations.
        !           191: 2.\&
        !           192: to use buffers.
        !           193: .H buffer pool\ 
        !           194: a region of 
        !           195: .C kernel
        !           196: memory available for holding
        !           197: .C blocks;
        !           198: non-\c
        !           199: .C raw
        !           200: input-output for
        !           201: .C block devices
        !           202: and
        !           203: .C file systems
        !           204: [3]
        !           205: goes through the buffer pool to make
        !           206: read and write operations
        !           207: independent of device format.
        !           208: .H cbreak\ 
        !           209: a mode of terminal input in which every character not a
        !           210: .C special character
        !           211: becomes available to a
        !           212: .I read (2)
        !           213: operation as soon as it is typed, instead of being
        !           214: .C buffered
        !           215: up to a
        !           216: .C newline
        !           217: or
        !           218: .C EOT character.
        !           219: .H change time\ 
        !           220: the most recent
        !           221: .C time
        !           222: at which the contents of a
        !           223: .C file
        !           224: [2] or its
        !           225: .C inode
        !           226: properties (e.g.
        !           227: .C owner
        !           228: and
        !           229: .I mode )
        !           230: were altered;
        !           231: cf.\&
        !           232: .C modification time.
        !           233: .H character\ 
        !           234: 1.\&
        !           235: a unit of store, usually 8 bits;
        !           236: a byte.
        !           237: 2.\&
        !           238: a token of the
        !           239: ASCII
        !           240: code, with octal value in the range 0 to 0177.
        !           241: .H character device\ 
        !           242: a
        !           243: .C device,
        !           244: such as a terminal or the
        !           245: .C null device,
        !           246: that cannot contain a
        !           247: .C file system
        !           248: [3];
        !           249: cf.\&
        !           250: .C block device.
        !           251: .H child process\ 
        !           252: see
        !           253: .C fork.
        !           254: .H client\ 
        !           255: a
        !           256: .C process
        !           257: that uses a service by 
        !           258: .C opening 
        !           259: the interface to a
        !           260: .C server.
        !           261: .H close\ 
        !           262: to make an
        !           263: .C open file
        !           264: unavailable for input or output; converse of
        !           265: .C open.
        !           266: .H command\ 
        !           267: 1.\&
        !           268: an instruction to the
        !           269: .C shell
        !           270: [1], usually to run a
        !           271: .C program
        !           272: [1] as a
        !           273: .C child process.
        !           274: 2.\&
        !           275: by extension, any
        !           276: .C executable file,
        !           277: especially a
        !           278: .C utility program.
        !           279: .H command file\ 
        !           280: same as
        !           281: .C shell script.
        !           282: .H connection line discipline\ 
        !           283: a
        !           284: .C line discipline
        !           285: used on
        !           286: .C mounted streams
        !           287: whereby each 
        !           288: .C opening
        !           289: of the stream provides a new
        !           290: .C pipe
        !           291: to the stream's
        !           292: .C server; 
        !           293: see
        !           294: .I connld (4).
        !           295: .H connection service\ 
        !           296: a collection of
        !           297: .C mounted streams,
        !           298: conventionally in
        !           299: .C directory
        !           300: .CW /cs ,
        !           301: that encapsulate generic setup protocols to reach
        !           302: .C servers;
        !           303: see
        !           304: .I ipc (3).
        !           305: .H control character\ 
        !           306: an
        !           307: ASCII
        !           308: character with octal code 0-037 or 0177, which does not
        !           309: print but may otherwise affect the behavior of a terminal;
        !           310: cf.\&
        !           311: .C special character.
        !           312: .H control stream, control terminal\ 
        !           313: a
        !           314: .C stream
        !           315: [2] associated with a
        !           316: .C process
        !           317: from which the process may receive
        !           318: .C interrupt,
        !           319: .C quit,
        !           320: and
        !           321: .C hangup
        !           322: signals; cf.\&
        !           323: .C process group.
        !           324: The control stream is conventionally 
        !           325: .CW /dev/tty ,
        !           326: .C file descriptor
        !           327: 3.\&
        !           328: .H cooked\ 
        !           329: not
        !           330: .C raw
        !           331: [1],
        !           332: said of an input
        !           333: .C stream 
        !           334: [2] in which 
        !           335: .C special characters
        !           336: are active.
        !           337: .H cookie\ 
        !           338: a peculiar goody, token, saying, or remembrance returned by or
        !           339: presented to a 
        !           340: .C program
        !           341: [3], cf.\&
        !           342: .C file descriptor,
        !           343: .C process number.
        !           344: .H core file\ 
        !           345: a
        !           346: .C core image
        !           347: of a terminated
        !           348: .C process
        !           349: saved for debugging; a core file is created under the name
        !           350: .CW core
        !           351: in the
        !           352: .C current directory
        !           353: of the process.
        !           354: .H core image\ 
        !           355: the data of a running or terminated
        !           356: .C process;
        !           357: the data may reside physically in main store, in the
        !           358: .C swap area,
        !           359: or in a
        !           360: .C core file,
        !           361: and logically in a
        !           362: .C process file.
        !           363: .H create\ 
        !           364: to
        !           365: .C open
        !           366: a file for writing, bringing it into existence as a
        !           367: .C plain file
        !           368: if necessary, and discarding any data it may have
        !           369: contained previously; cf.\&
        !           370: .C unlink.
        !           371: .H current directory, working directory\ 
        !           372: the directory from which
        !           373: .C relative pathnames
        !           374: begin; a current directory is associated with each
        !           375: .C process.
        !           376: .H daemon\ 
        !           377: a
        !           378: .C background
        !           379: process, often perpetual, that performs a system-wide public function, e.g.
        !           380: .I calendar (1)
        !           381: and
        !           382: .I cron (8);
        !           383: the affected spelling is an ancient legacy; cf.\&
        !           384: .C server.
        !           385: .H Datakit\ 
        !           386: AT&T trademark for
        !           387: a data network based on virtual circuit switching.
        !           388: .H data segment\ 
        !           389: see
        !           390: .C segment.
        !           391: .H date\ 
        !           392: same as
        !           393: .C time.
        !           394: .H device\ 
        !           395: 1.\&
        !           396: a
        !           397: .C file
        !           398: [2]
        !           399: that is not a
        !           400: .C plain file
        !           401: or a
        !           402: .C directory,
        !           403: examples are tape drive, terminal, a span of 
        !           404: .C blocks
        !           405: on a disk drive, or the
        !           406: .C null device;
        !           407: a
        !           408: .C special file.
        !           409: 2.\&
        !           410: a physical input-output unit.
        !           411: .H device number\ 
        !           412: a system-dependent code used in
        !           413: .C inodes
        !           414: to distinguish
        !           415: .C devices
        !           416: [1].
        !           417: A device number has two parts:
        !           418: .HI major device
        !           419: for the type of the device and
        !           420: .HI minor device
        !           421: for an individual device of a type.
        !           422: .H directory\ 
        !           423: a
        !           424: .C file
        !           425: [2] that comprises a catalog of
        !           426: .C filenames
        !           427: [2];
        !           428: the organizing principle of the
        !           429: .C file system
        !           430: [2],
        !           431: a directory
        !           432: consists of
        !           433: .C entries
        !           434: which specify further
        !           435: files [2], including directories,
        !           436: and constitutes a node of the
        !           437: .C directory tree.
        !           438: .H directory entry, entry\ 
        !           439: 1.\&
        !           440: an association of a name with an
        !           441: .C inode number
        !           442: appearing as an element of a
        !           443: .C directory.
        !           444: 2.\&
        !           445: the name part of such an association.
        !           446: .H directory hierarchy, directory tree, file hierarchy\ 
        !           447: the tree of all
        !           448: .C directories, 
        !           449: in which each is reachable from the
        !           450: .C root
        !           451: [2]
        !           452: via a
        !           453: .C path
        !           454: of
        !           455: .C subdirectories.
        !           456: .H driver\ 
        !           457: a set of
        !           458: .C kernel
        !           459: subroutines that handle input/output for a given
        !           460: .C major device
        !           461: type.
        !           462: .H echo\ 
        !           463: to transmit characters received from a terminal back to it;
        !           464: the technique of echoing to a
        !           465: .C full duplex
        !           466: terminal provides acknowledgement of typed input.
        !           467: .H effective userid\ 
        !           468: see
        !           469: .C set userid.
        !           470: .H end of file\ 
        !           471: the condition of the
        !           472: .C read pointer
        !           473: being past the last character of an
        !           474: .C open file.
        !           475: End of file is signified by a read operation
        !           476: returning zero bytes, or by an EOF return
        !           477: from functions of the
        !           478: .C stdio
        !           479: package; it may be simulated from a terminal by
        !           480: typing EOT (control-D) after a
        !           481: .C newline.
        !           482: .H entry\ 
        !           483: see
        !           484: .C directory entry.
        !           485: .H environment\ 
        !           486: 1.\&
        !           487: a set of strings, distinct from the
        !           488: .C arguments,
        !           489: made available to a
        !           490: .C process
        !           491: when it
        !           492: .C executes
        !           493: [1] a
        !           494: .C file;
        !           495: the environment is usually inherited across
        !           496: .I exec (2)
        !           497: operations.
        !           498: 2.\&
        !           499: a specific environment [1] maintained by the
        !           500: .C shell
        !           501: [1].
        !           502: 3.\&
        !           503: a nebulously identified way of doing things, as in
        !           504: `interactive environment': deprecated usage, not always expunged
        !           505: from these manuals.
        !           506: .H EOF\ 
        !           507: 1.\&
        !           508: same as
        !           509: .C end of file.
        !           510: 2.\&
        !           511: a conventional value returned at end of file by
        !           512: .C stdio
        !           513: functions.
        !           514: .H EOT, EOT character\ 
        !           515: 1.\&
        !           516: the
        !           517: ASCII
        !           518: `end of transmission' character, control-D, octal code 04.
        !           519: 2.\&
        !           520: a character that ends (and is excluded from) data
        !           521: obtained by
        !           522: .I read (2)
        !           523: from a terminal; EOT at the beginning of a line causes the
        !           524: .C end of file
        !           525: condition.
        !           526: .H epoch\ 
        !           527: see
        !           528: .C time.
        !           529: .H erase character\ 
        !           530: a
        !           531: .C special character
        !           532: [2] which, when received from a terminal, is deleted
        !           533: together with the character immediately preceding it on the line;
        !           534: usually defaulted to
        !           535: .CW #
        !           536: or backspace, the erase character may be changed by
        !           537: .I stty (1);
        !           538: cf.\&
        !           539: .C kill character.
        !           540: .H escape character\ 
        !           541: 1.\&
        !           542: The ASCII character ESC, octal 033.
        !           543: 2.\&
        !           544: a
        !           545: .C special character
        !           546: that may cause the following character
        !           547: to have other than its usual meaning;
        !           548: the default escape character in terminal input is 
        !           549: .CW \e .
        !           550: .H executable file, object program\ 
        !           551: 1.\&
        !           552: an
        !           553: .C  object file 
        !           554: that is ready to be copied into the
        !           555: address space
        !           556: of a
        !           557: .C process
        !           558: to run as the code of that process.
        !           559: 2.\&
        !           560: a file that has
        !           561: execute
        !           562: .C permission,
        !           563: either an
        !           564: .C executable file
        !           565: [1] or a
        !           566: .C shell script.
        !           567: .H execute, exec\ 
        !           568: 1.\&
        !           569: to replace the
        !           570: .C text segment
        !           571: and
        !           572: .C data segments
        !           573: of a
        !           574: .C process
        !           575: with a given
        !           576: .C program
        !           577: [1]; see
        !           578: .I exec (2).
        !           579: 2.\&
        !           580: informally, to run a
        !           581: .C program.
        !           582: .H exit\ 
        !           583: to terminate a
        !           584: .C process;
        !           585: exit is voluntary, in contrast to
        !           586: .C kill.
        !           587: .H exit status, return code\ 
        !           588: an integer value denoting the outcome of a
        !           589: .C process,
        !           590: including an indication of the cause of termination.
        !           591: .H export\ 
        !           592: 1.\&
        !           593: to include in the 
        !           594: .C environment
        !           595: [1] of a
        !           596: .C process
        !           597: when it is
        !           598: .C executed
        !           599: [1],
        !           600: said of a string.
        !           601: .H external\ 
        !           602: known beyond the scope of a single compilation,
        !           603: said of names of data and functions in a program.
        !           604: .H file\ 
        !           605: 1.\&
        !           606: in general, a potential source of input or destination for output.
        !           607: 2.\&
        !           608: most specifically, an
        !           609: .C inode
        !           610: and/or associated contents, i.e. a
        !           611: .C plain file,
        !           612: a
        !           613: .C special file,
        !           614: or a
        !           615: .C directory.
        !           616: 3.\&
        !           617: a
        !           618: .C directory entry
        !           619: [1];
        !           620: several directory entries may name the same file [2].
        !           621: 4.\&
        !           622: most loosely, a
        !           623: .C plain file.
        !           624: .H file descriptor\ 
        !           625: a conventional integer quantity, or
        !           626: .C cookie,
        !           627: that designates an
        !           628: .C open file;
        !           629: cf.\&
        !           630: .C stream
        !           631: [1].
        !           632: .H file descriptor file\ 
        !           633: a
        !           634: .C special file
        !           635: that serves as a name for an
        !           636: .C open file
        !           637: [1]; see
        !           638: .I fd (4).
        !           639: .H file hierarchy\ 
        !           640: same as
        !           641: .C directory hierarchy.
        !           642: .H filename\ 
        !           643: 1.\&
        !           644: a
        !           645: .C pathname.
        !           646: 2.\&
        !           647: same as
        !           648: .C basename.
        !           649: .H file pointer\ 
        !           650: the number of the next byte that would normally
        !           651: be read or written in a
        !           652: .C file
        !           653: [2]; also called
        !           654: .C read pointer,
        !           655: .C write pointer,
        !           656: or 
        !           657: .C seek pointer.
        !           658: .H file system\ 
        !           659: 1.\&
        !           660: a detachable part of the
        !           661: .C directory hierarchy.
        !           662: 2.\&
        !           663: the collection of all 
        !           664: .C files
        !           665: [2] accessible to a computer,
        !           666: organized into a
        !           667: directory hierarchy.
        !           668: 3.\&
        !           669: in particular a
        !           670: .C block device
        !           671: in which
        !           672: .C files
        !           673: [2] are organized according to an
        !           674: .C i-list
        !           675: and accessed by
        !           676: .C paths
        !           677: through 
        !           678: .C directories.
        !           679: .H file system switch\ 
        !           680: a
        !           681: .C kernel
        !           682: table that directs the interpretation of
        !           683: operations in
        !           684: .C file systems
        !           685: [1] and 
        !           686: .C special file systems.
        !           687: .H file times\ 
        !           688: .C access time,
        !           689: .C change time,
        !           690: and
        !           691: .C modification time.
        !           692: .H filter\ 
        !           693: a
        !           694: .C program
        !           695: [1]
        !           696: that reads from the
        !           697: .C standard input
        !           698: and writes on the
        !           699: .C standard output,
        !           700: so called because it can be used as a data-transformer in a
        !           701: .C pipeline.
        !           702: .H flag\ 
        !           703: same as
        !           704: .C option.
        !           705: .H flush\ 
        !           706: to empty a
        !           707: .C buffer,
        !           708: for example to throw away unwanted input-output upon
        !           709: .C interrupt
        !           710: or to release output from the clutches of
        !           711: .C stdio.
        !           712: .H foreground\ 
        !           713: running under direct control of a terminal, said of a
        !           714: .C process;
        !           715: converse of
        !           716: .C background.
        !           717: .H fork\ 
        !           718: 1.\&
        !           719: to split one
        !           720: .C process
        !           721: into two, the
        !           722: .HI parent process
        !           723: and
        !           724: .HI child process,
        !           725: with separate, but initially identical,
        !           726: .C text, data,
        !           727: and
        !           728: .C stack
        !           729: .C segments.
        !           730: 2.\&
        !           731: informally, same as
        !           732: .C spawn.
        !           733: .H free list\ 
        !           734: in a
        !           735: .C file system
        !           736: [1],
        !           737: the list of
        !           738: .C blocks
        !           739: that are not occupied by data.
        !           740: .H full duplex\ 
        !           741: 1.\&
        !           742: capable of carrying information simultaneously in both directions,
        !           743: said of a communication channel.
        !           744: 2.\&
        !           745: transmitting what is typed while printing what is received,
        !           746: said of a terminal, or of terminal communication;
        !           747: cf.\&
        !           748: .C half duplex
        !           749: and
        !           750: .C echo.
        !           751: .H gid\ 
        !           752: see
        !           753: .C groupid.
        !           754: .H global\ 
        !           755: same as
        !           756: .C external.
        !           757: .H group\ 
        !           758: 1.\&
        !           759: a set of
        !           760: .C permissions
        !           761: alternative to
        !           762: .C owner
        !           763: permissions for access to a
        !           764: .C file.
        !           765: 2.\&
        !           766: a set of
        !           767: .C userids
        !           768: that may assume the privileges of a group [1].
        !           769: 3.\&
        !           770: the
        !           771: .C groupid
        !           772: of a 
        !           773: .C file.
        !           774: .H group file\ 
        !           775: the file
        !           776: .CW /etc/group ,
        !           777: which tells which
        !           778: .C groupids
        !           779: are available to each
        !           780: .C login name.
        !           781: .H groupid, gid\ 
        !           782: an integer value associated with
        !           783: .C processes
        !           784: and
        !           785: .C files
        !           786: [2] used in determining
        !           787: .C permissions.
        !           788: .H half duplex\ 
        !           789: 1.\&
        !           790: capable of carrying information in both directions, but not simultaneously,
        !           791: said of a communication channel.
        !           792: 2.\&
        !           793: transmitting (usually typing what is transmitted) and receiving,
        !           794: but not simultaneously, said of a terminal; cf.\&
        !           795: .C full duplex.
        !           796: .H hang\ 
        !           797: 1.\&
        !           798: to 
        !           799: .C execute
        !           800: a
        !           801: .C program
        !           802: [1] so that it stops immediately, usually for debugging; cf.\&
        !           803: .I hang (1).
        !           804: 2.\&
        !           805: to wait for something that won't happen; said of a process.
        !           806: .H hangup\ 
        !           807: a
        !           808: .C signal
        !           809: indicating that a user's terminal
        !           810: has been disconnected.
        !           811: .H hard link\ 
        !           812: 1.\&
        !           813: a 
        !           814: .C directory entry
        !           815: [1] that does not designate a
        !           816: .C symbolic link.
        !           817: 2.\&
        !           818: a
        !           819: .C link
        !           820: [2] that is not a
        !           821: .C symbolic link.
        !           822: .H header file\ 
        !           823: same as
        !           824: .C include file;
        !           825: the name of a header file customarily ends with 
        !           826: .CW \&.h
        !           827: (dot-h).
        !           828: .H here file\ 
        !           829: in a
        !           830: .C shell script,
        !           831: literally given input data for a
        !           832: .C command;
        !           833: here files are introduced by 
        !           834: .CW << .
        !           835: .H hole\ 
        !           836: a gap in a 
        !           837: .C plain file
        !           838: caused by
        !           839: .C seeking
        !           840: while writing; 
        !           841: .I read (2)
        !           842: takes data in holes to be zero;
        !           843: a
        !           844: .C block 
        !           845: in a hole occupies no space in its
        !           846: .C file system
        !           847: [1].
        !           848: .H home directory\ 
        !           849: 1.\&
        !           850: the
        !           851: .C current directory
        !           852: established for each user upon
        !           853: .C logging in.
        !           854: 2.\&
        !           855: the variable 
        !           856: .CW HOME
        !           857: in the
        !           858: .C environment
        !           859: [2], used in particular as the default destination for the 
        !           860: .C shell
        !           861: [1]
        !           862: .CW cd
        !           863: command.
        !           864: .H host process\ 
        !           865: a
        !           866: .C process
        !           867: working in collaboration with a
        !           868: .C terminal process.
        !           869: .H HZ\ 
        !           870: alternating-current line frequency,
        !           871: 60 in North America, 50 in most other places.
        !           872: .H i-list\ 
        !           873: the index to a
        !           874: .C file system
        !           875: [1]
        !           876: listing all the
        !           877: .C inodes
        !           878: of the file system; cf.\&
        !           879: .C inode number.
        !           880: .H image\ 
        !           881: same as
        !           882: .C core image.
        !           883: .H include file, header file\ 
        !           884: a
        !           885: .C file
        !           886: [4],
        !           887: usually containing shared data declarations,
        !           888: that is to be copied into source programs as they are compiled.
        !           889: .H inode\ 
        !           890: an element of a
        !           891: .C file system
        !           892: [1];
        !           893: an inode specifies all properties of a particular
        !           894: .C file
        !           895: [2] and locates the file's contents, if any.
        !           896: .H inode number, i-number\ 
        !           897: the position of an
        !           898: .C inode
        !           899: in the
        !           900: .C i-list
        !           901: of a
        !           902: .C file system
        !           903: [1].
        !           904: .H Internet\ 
        !           905: an informal association of data networks using
        !           906: protocols developed mainly under the auspices of
        !           907: DARPA.
        !           908: .H interrupt\ 
        !           909: 1.\&
        !           910: a
        !           911: .C signal
        !           912: that normally terminates a
        !           913: .C process,
        !           914: caused by a
        !           915: .C break
        !           916: [1]
        !           917: or an
        !           918: .C interrupt character;
        !           919: cf.\&
        !           920: .C quit.
        !           921: 2.\&
        !           922: loosely, any
        !           923: .C signal.
        !           924: .H interrupt character\ 
        !           925: a character (normally
        !           926: ASCII
        !           927: DEL) that, when typed on a
        !           928: .C control terminal,
        !           929: causes an
        !           930: .C interrupt.
        !           931: .H io control, ioctl\ 
        !           932: 1.\&
        !           933: a
        !           934: .C system call
        !           935: that changes the behavior of an
        !           936: .C open file,
        !           937: for example in interpreting
        !           938: .C  control characters.
        !           939: 2.\&
        !           940: a function performed by 
        !           941: .I ioctl (2).
        !           942: .H jerq\ 
        !           943: vernacular name for a Teletype 5620 terminal.
        !           944: .H K\ 
        !           945: 1024; 1024 bytes: a `4K file system' has 4096-byte
        !           946: .C blocks.
        !           947: .H kernel\ 
        !           948: the UNIX system proper;
        !           949: resident code that implements the
        !           950: .C system calls.
        !           951: .H kernel space, kernel address space\ 
        !           952: data and code that are addressable only by the
        !           953: .C kernel.
        !           954: .H kill\ 
        !           955: 1.\&
        !           956: a particular
        !           957: .C signal
        !           958: guaranteed to terminate a
        !           959: .C process.
        !           960: 2.\&
        !           961: by extension, to send any
        !           962: .C signal
        !           963: to a
        !           964: .C process.
        !           965: 3.\&
        !           966: the
        !           967: .C kill character.
        !           968: .H kill character\ 
        !           969: a
        !           970: .C special character,
        !           971: which, when received from a terminal, is deleted together with
        !           972: all preceding characters on the line;
        !           973: defaulted to
        !           974: .CW @ ,
        !           975: the kill character may be changed by
        !           976: .I stty (1);
        !           977: cf.\&
        !           978: .C erase character.
        !           979: .H layer\ 
        !           980: a virtual terminal appearing on a screen and also capable
        !           981: of running
        !           982: .C terminal processes.
        !           983: The
        !           984: .C processes
        !           985: associated with each layer constitute
        !           986: a separate
        !           987: .C process group.
        !           988: .H library\ 
        !           989: an
        !           990: .C archive
        !           991: [2] of
        !           992: .C object files
        !           993: from which the
        !           994: .C link editor
        !           995: may select functions and data as needed.
        !           996: .H line\ 
        !           997: in a
        !           998: .C text file,
        !           999: a sequence of bytes terminated by a
        !          1000: .C newline.
        !          1001: .H line discipline\ 
        !          1002: a module to handle protocol or data
        !          1003: conversion for a
        !          1004: .C stream
        !          1005: [2].
        !          1006: A line discipline, unlike a
        !          1007: .C filter,
        !          1008: is part of the 
        !          1009: .C kernel.
        !          1010: .H link\ 
        !          1011: 1.\&
        !          1012: to add
        !          1013: an entry for an existing
        !          1014: .C file
        !          1015: [2] to a directory;
        !          1016: converse of
        !          1017: .C unlink.
        !          1018: 2.\&
        !          1019: particularly, any but one putatively primary directory entry for
        !          1020: a given
        !          1021: .C inode,
        !          1022: either linked [1] or a
        !          1023: .C symbolic link.
        !          1024: .H link count\ 
        !          1025: the number of
        !          1026: .C directory entries
        !          1027: [1] that pertain to an
        !          1028: .C inode;
        !          1029: a
        !          1030: .C file
        !          1031: [2] ceases to exist
        !          1032: when its link count becomes zero
        !          1033: and it is not 
        !          1034: .C open.
        !          1035: .H link editor, loader\ 
        !          1036: the utility
        !          1037: .I ld (1),
        !          1038: which combines separately compiled
        !          1039: .C object files
        !          1040: into a single
        !          1041: object file.
        !          1042: .H listen\ 
        !          1043: to issue a read on a
        !          1044: .C stream,
        !          1045: waiting for data, usually a service request, from some other
        !          1046: .C process
        !          1047: or
        !          1048: .C remote
        !          1049: source.
        !          1050: .H loader\ 
        !          1051: same as
        !          1052: .C link editor.
        !          1053: .H log in\ 
        !          1054: to identify one's self as a user and start a computing session.
        !          1055: .H login\ 
        !          1056: 1.\&
        !          1057: the 
        !          1058: .C program
        !          1059: that controls logging in.
        !          1060: 2.\&
        !          1061: the act of
        !          1062: .C logging in.
        !          1063: 3.\&
        !          1064: by extension, the computing session that follows a login
        !          1065: [2].
        !          1066: .H login name\ 
        !          1067: the name by which a person is identified when
        !          1068: .C logging in;
        !          1069: cf.\&
        !          1070: .C userid.
        !          1071: .H magic number\ 
        !          1072: a
        !          1073: .C cookie
        !          1074: that distinguishes various flavors of
        !          1075: .C object file;
        !          1076: see
        !          1077: .I a.out (5).
        !          1078: .H major device\ 
        !          1079: see
        !          1080: .C device number.
        !          1081: .H makefile, mkfile\ 
        !          1082: a list of dependencies among files and recipes for updating 
        !          1083: them, usually by recompilation,
        !          1084: used by
        !          1085: .I make (1)
        !          1086: or
        !          1087: .I mk (1)
        !          1088: to maintain self-consistent software;
        !          1089: `mkfile' rhymes with `book file'.
        !          1090: .H manager\ 
        !          1091: same as
        !          1092: .C server.
        !          1093: .H memory image\ 
        !          1094: same as
        !          1095: .C core image.
        !          1096: .H message line discipline\ 
        !          1097: a
        !          1098: .C line discipline
        !          1099: used on
        !          1100: .C pipes
        !          1101: wherein a record of each
        !          1102: .C system call
        !          1103: on one end of the pipe is received as a message
        !          1104: at the other end; see
        !          1105: .I mesgld (4).
        !          1106: .H minor device\ 
        !          1107: see
        !          1108: .C device number.
        !          1109: .H mode, file mode\ 
        !          1110: the
        !          1111: .C permissions
        !          1112: of a
        !          1113: .C file;
        !          1114: colloquially referred to by a 3-digit octal number, e.g. `a 755 file';
        !          1115: see
        !          1116: .I chmod (1).
        !          1117: .H modification time\ 
        !          1118: the most recent
        !          1119: .C time
        !          1120: at which the contents of a
        !          1121: .C file
        !          1122: [2] were altered;
        !          1123: cf.\&
        !          1124: .C access time,
        !          1125: .C change time.
        !          1126: .H mount\ 
        !          1127: to associate with a
        !          1128: .C directory entry
        !          1129: [2] a 
        !          1130: .C stream
        !          1131: [2] or the
        !          1132: .C root
        !          1133: [1]
        !          1134: of a
        !          1135: .C file system
        !          1136: [1],
        !          1137: making respectively a virtual file
        !          1138: or an extended
        !          1139: .C file system
        !          1140: [2].
        !          1141: Mounting assigns to the
        !          1142: .C inode
        !          1143: of a directory entry a temporary meaning,
        !          1144: which ceases with the associated
        !          1145: .C server
        !          1146: [1],
        !          1147: with explicit unmounting,
        !          1148: or with
        !          1149: .C booting.
        !          1150: .H mounted stream\ 
        !          1151: a 
        !          1152: .C directory entry
        !          1153: [2] on which an open
        !          1154: .C stream
        !          1155: [2]
        !          1156: has been
        !          1157: .C mounted.
        !          1158: .H named pipe\ 
        !          1159: same as
        !          1160: .C mounted stream.
        !          1161: .H namelist\ 
        !          1162: same as
        !          1163: .C symbol table.
        !          1164: .H network file system\ 
        !          1165: a mechanism for cross-\c
        !          1166: .C mounting
        !          1167: the
        !          1168: .C file systems
        !          1169: [2] of different computers; see
        !          1170: .I netfs (8).
        !          1171: .H newline\ 
        !          1172: the combined function of carriage return and line feed,
        !          1173: represented by the
        !          1174: ASCII
        !          1175: character LF, octal value 012;
        !          1176: separates
        !          1177: .C lines
        !          1178: in a
        !          1179: .C text file;
        !          1180: newline is evoked by the `return' key on most terminals.
        !          1181: .H nice\ 
        !          1182: to place a 
        !          1183: .C process
        !          1184: in
        !          1185: .C nice mode
        !          1186: [2].
        !          1187: .H nice mode\ 
        !          1188: 1.\&
        !          1189: the scheduling priority of a
        !          1190: .C process;
        !          1191: see
        !          1192: .I nice (2).
        !          1193: 2.\&
        !          1194: in particular, a low priority.
        !          1195: .H null device\ 
        !          1196: a
        !          1197: .C device 
        !          1198: [1] that always yields
        !          1199: .C end of file
        !          1200: on reading and discards all data on writing.
        !          1201: .H null pointer\ 
        !          1202: in C, a pointer object with value 0.
        !          1203: .H object file\ 
        !          1204: a
        !          1205: .C file
        !          1206: [2] that contains machine language code and data;
        !          1207: object files are produced from source programs by compilers
        !          1208: and from other object files and
        !          1209: .C libraries
        !          1210: by the
        !          1211: .C link editor;
        !          1212: an object file that is ready to run is an
        !          1213: .C executable file
        !          1214: [1].
        !          1215: .H open\ 
        !          1216: to make a
        !          1217: .C file
        !          1218: [2] available for writing or reading, with the
        !          1219: .C file pointer
        !          1220: positioned at byte 0;
        !          1221: converse of
        !          1222: .C close;
        !          1223: cf.\&
        !          1224: .C create.
        !          1225: .H open file\ 
        !          1226: 1.\&
        !          1227: the destination for input or output obtained by
        !          1228: .C opening
        !          1229: a
        !          1230: .C file
        !          1231: [2] or creating a
        !          1232: .C pipe;
        !          1233: a
        !          1234: .C file descriptor;
        !          1235: open files are shared across
        !          1236: .C forks
        !          1237: and persist across
        !          1238: .C executes 
        !          1239: [2].
        !          1240: 2.\&
        !          1241: loosely, a 
        !          1242: .C file
        !          1243: [2]
        !          1244: that has been opened.
        !          1245: .H option\ 
        !          1246: an
        !          1247: .C argument
        !          1248: that affects the way a
        !          1249: .C command
        !          1250: works; option names customarily begin with 
        !          1251: .CW - .
        !          1252: .H ordinary file\ 
        !          1253: same as
        !          1254: .C plain file.
        !          1255: .H other\ 
        !          1256: 1.\&
        !          1257: the category of
        !          1258: .C permissions
        !          1259: regulating access to a 
        !          1260: .C file
        !          1261: [2] by processes with
        !          1262: .C userid
        !          1263: different from the
        !          1264: .C owner
        !          1265: and
        !          1266: .C groupid
        !          1267: different from the
        !          1268: .C group
        !          1269: of the file.
        !          1270: 2.\&
        !          1271: the customary name of the default 
        !          1272: .C group
        !          1273: [2] assigned upon 
        !          1274: .C login
        !          1275: [2].
        !          1276: .H owner\ 
        !          1277: a
        !          1278: .C userid
        !          1279: associated with a 
        !          1280: .C file
        !          1281: [2], usually
        !          1282: that of the
        !          1283: .C process
        !          1284: that created it;
        !          1285: the owner has distinctive
        !          1286: .C permissions
        !          1287: for a file.
        !          1288: .H page\ 
        !          1289: a hardware-dependent unit of virtual memory management,
        !          1290: defined in
        !          1291: .CW /usr/include/sys/types.h ;
        !          1292: cf.\&
        !          1293: .C block.
        !          1294: .H parent directory\ 
        !          1295: the
        !          1296: .C directory
        !          1297: next nearer the
        !          1298: .C  root 
        !          1299: than a given directory;
        !          1300: the inverse of a
        !          1301: .C subdirectory.
        !          1302: A
        !          1303: .C directory entry
        !          1304: [2]
        !          1305: .CW ..
        !          1306: always refers to the parent directory.
        !          1307: .H parent process\ 
        !          1308: see
        !          1309: .C fork.
        !          1310: .H password\ 
        !          1311: a secret word used to confirm a user's right to
        !          1312: .C log in
        !          1313: under a particular
        !          1314: .C userid;
        !          1315: passwords are encrypted by a one-way algorithm and kept in the
        !          1316: .C password file.
        !          1317: .H password file\ 
        !          1318: a record of all
        !          1319: .C login names
        !          1320: with the
        !          1321: .C password,
        !          1322: .C userid,
        !          1323: .C groupid,
        !          1324: .C home directory,
        !          1325: and
        !          1326: .C shell
        !          1327: [2] for each, used to control access to the system.
        !          1328: .H path, pathname\ 
        !          1329: a chain of names designating a
        !          1330: .C file;
        !          1331: a
        !          1332: .HI relative pathname
        !          1333: leads from the
        !          1334: .C current directory,
        !          1335: for example, a path to
        !          1336: .C directory
        !          1337: .CW A ,
        !          1338: thence to directory 
        !          1339: .CW B ,
        !          1340: thence to 
        !          1341: .C file
        !          1342: [2]
        !          1343: .CW C
        !          1344: is denoted 
        !          1345: .CW A/B/C ;
        !          1346: a
        !          1347: .HI full pathname
        !          1348: begins at the
        !          1349: .C root
        !          1350: [2],
        !          1351: indicated by an initial 
        !          1352: .CW / ,
        !          1353: as in
        !          1354: .CW /A/B/C .
        !          1355: .H permission\ 
        !          1356: a right to access a
        !          1357: .C file
        !          1358: [2] in a particular way: read, write, execute (or look up in, if a directory);
        !          1359: permissions are granted separately to
        !          1360: .C owner,
        !          1361: .C group,
        !          1362: and
        !          1363: .C others.
        !          1364: .HI permission bit\ 
        !          1365: a permission, so called because each permission is encoded into
        !          1366: one bit in an
        !          1367: .C inode.
        !          1368: .H pid\ 
        !          1369: see
        !          1370: .C process id.
        !          1371: .H pipe\ 
        !          1372: a nameless
        !          1373: .C stream
        !          1374: [2] connection between
        !          1375: .C processes,
        !          1376: whereby data written on an
        !          1377: .C open file
        !          1378: in one process may be read in another; cf.\&
        !          1379: .C named pipe.
        !          1380: .H pipeline\ 
        !          1381: a sequence of
        !          1382: .C programs
        !          1383: [1]
        !          1384: connected by
        !          1385: .C pipes.
        !          1386: .H plain file, ordinary file\ 
        !          1387: a
        !          1388: .C file
        !          1389: [2] that is neither a
        !          1390: .C special file
        !          1391: nor a
        !          1392: .C directory;
        !          1393: plain files are the customary repository of data.
        !          1394: .H priority\ 
        !          1395: see
        !          1396: .C nice mode
        !          1397: [1].
        !          1398: .H process\ 
        !          1399: a connected sequence of computation;
        !          1400: a process is characterized by a
        !          1401: .C core image
        !          1402: with instruction location counter,
        !          1403: .C current directory,
        !          1404: a set of
        !          1405: .C open files,
        !          1406: .C control stream,
        !          1407: .C userid,
        !          1408: and
        !          1409: .C groupid.
        !          1410: .H process directory\ 
        !          1411: a
        !          1412: .C special file system,
        !          1413: .CW /proc ,
        !          1414: in which all
        !          1415: .C process files
        !          1416: appear.
        !          1417: .H process file\ 
        !          1418: a
        !          1419: .C core image
        !          1420: of a
        !          1421: .C process,
        !          1422: accessible as a
        !          1423: .C file
        !          1424: [3].
        !          1425: .H process group\ 
        !          1426: a set of processes that share a
        !          1427: .C control stream
        !          1428: and among which
        !          1429: .C signals
        !          1430: may be broadcast;
        !          1431: process groups are created upon
        !          1432: .C logging in,
        !          1433: creating a window, or
        !          1434: issuing certain
        !          1435: .C io controls;
        !          1436: see
        !          1437: .I stream (4).
        !          1438: .H process number, process id, pid\ 
        !          1439: an integer that identifies a
        !          1440: .C process.
        !          1441: .H profile\ 
        !          1442: 1.\&
        !          1443: an optional
        !          1444: .C shell script,
        !          1445: .CW \&.profile ,
        !          1446: used by the
        !          1447: .C shell
        !          1448: [1] upon
        !          1449: .C logging in
        !          1450: to establish the
        !          1451: .C environment
        !          1452: [3]
        !          1453: and other working conditions customary to a particular user.
        !          1454: 2.\&
        !          1455: to collect a histogram of values of the instruction location counter of a
        !          1456: .C process;
        !          1457: see
        !          1458: .I monitor (3).
        !          1459: .H program\ 
        !          1460: 1.\&
        !          1461: an
        !          1462: .C executable file.
        !          1463: 2.\&
        !          1464: a
        !          1465: .C process.
        !          1466: 3.\&
        !          1467: all the usual meanings.
        !          1468: .H program break\ 
        !          1469: the first address beyond the
        !          1470: .C static
        !          1471: data accessible to a
        !          1472: .C process;
        !          1473: the program break may be
        !          1474: adjusted by
        !          1475: .I brk (2).
        !          1476: .H quit\ 
        !          1477: a
        !          1478: .C signal
        !          1479: that normally terminates a
        !          1480: .C process,
        !          1481: caused by a
        !          1482: .HI quit character
        !          1483: (normally control-\e);
        !          1484: quit differs from
        !          1485: .C interrupt
        !          1486: in that quit creates a
        !          1487: .C core file
        !          1488: for the terminated process.
        !          1489: .H random library\ 
        !          1490: a
        !          1491: .C library
        !          1492: that contains an index to 
        !          1493: .C external
        !          1494: names;
        !          1495: a library is made into a random library by
        !          1496: .C ranlib
        !          1497: see
        !          1498: .I ar (1).
        !          1499: Nonrandom libraries must be carefully ordered for the
        !          1500: .C link editor
        !          1501: to cope with cross references among the subroutines.
        !          1502: .H raw\ 
        !          1503: 1.\&
        !          1504: a mode of terminal input in which every character typed is passed
        !          1505: to a reading
        !          1506: .C process
        !          1507: and
        !          1508: .C special characters
        !          1509: lose their special character;
        !          1510: converse of
        !          1511: .C cooked.
        !          1512: 2.\&
        !          1513: said of input-output to a
        !          1514: .C raw device.
        !          1515: .H raw device\ 
        !          1516: a
        !          1517: .C device
        !          1518: [1],
        !          1519: read and write operations to which are not 
        !          1520: .C buffered,
        !          1521: and are synchronized to natural records of the physical device.
        !          1522: A raw device is usually a
        !          1523: .C character device
        !          1524: that addresses the same physical device as some
        !          1525: .C block device.
        !          1526: .H read ahead\ 
        !          1527: to fill input
        !          1528: .C buffers
        !          1529: in the
        !          1530: .C kernel
        !          1531: in advance of
        !          1532: .I read (2)
        !          1533: operations.
        !          1534: .H read pointer\ 
        !          1535: same as
        !          1536: .C file pointer.
        !          1537: .H real userid\ 
        !          1538: see
        !          1539: .C set userid.
        !          1540: .H reboot\ 
        !          1541: same as
        !          1542: .C boot.
        !          1543: .H regular expression\ 
        !          1544: 1.\&
        !          1545: an expression denoting a set of strings in a notation due to Kleene.
        !          1546: 2.\&
        !          1547: especially,
        !          1548: a restricted and modified form of regular expression used for pattern-matching in 
        !          1549: .I ed (1)
        !          1550: and elsewhere.
        !          1551: .H relative pathname\ 
        !          1552: see
        !          1553: .C pathname.
        !          1554: .H relocation bits, relocation information\ 
        !          1555: information in an
        !          1556: .C object file
        !          1557: that tells the
        !          1558: .C link editor
        !          1559: how to adjust addresses when combining it with other
        !          1560: .C object files;
        !          1561: `bits' is a fossilized misnomer.
        !          1562: .H return code\ 
        !          1563: same as
        !          1564: .C exit status.
        !          1565: .H root\ 
        !          1566: 1.\&
        !          1567: a distinguished directory that constitutes the origin of the
        !          1568: .C directory hierarchy
        !          1569: in a 
        !          1570: .C file system
        !          1571: [1].
        !          1572: 2.\&
        !          1573: specifically, the origin for the 
        !          1574: .C file system
        !          1575: [2], with the conventional
        !          1576: .C pathname
        !          1577: .CW / .
        !          1578: 3.\&
        !          1579: the conventional
        !          1580: .C login name
        !          1581: for the
        !          1582: .C super-user.
        !          1583: .H schedule\ 
        !          1584: to assign resources \- main store and CPU time \- to
        !          1585: .C processes.
        !          1586: .HI scheduler\ 
        !          1587: a permanent
        !          1588: .C process,
        !          1589: with
        !          1590: .C process number
        !          1591: 1, and associated
        !          1592: .C kernel
        !          1593: facilities that do scheduling.
        !          1594: .H search path\ 
        !          1595: a list of
        !          1596: .C pathnames
        !          1597: of
        !          1598: .C directories
        !          1599: that determines the meaning of a
        !          1600: .C command
        !          1601: [2] name.
        !          1602: In one form of
        !          1603: .C exec,
        !          1604: a
        !          1605: .C relative pathname
        !          1606: is prefixed with members of
        !          1607: the search path in turn until
        !          1608: a pathname of an
        !          1609: .C executable file
        !          1610: [2] results.
        !          1611: .H seek\ 
        !          1612: to set the
        !          1613: .C file pointer
        !          1614: to a specified place in an
        !          1615: .C open file.
        !          1616: .H seek pointer\ 
        !          1617: same as
        !          1618: .C file pointer.
        !          1619: .H segment\ 
        !          1620: a contiguous range of the
        !          1621: address space
        !          1622: of a
        !          1623: .C process
        !          1624: with consistent store access capabilities; the four segments are
        !          1625: (i) the
        !          1626: .HI text segment,
        !          1627: occupied by executable code,
        !          1628: (ii) the
        !          1629: .HI data segment,
        !          1630: occupied by
        !          1631: .C static
        !          1632: data that is
        !          1633: explicitly initialized,
        !          1634: (iii) the
        !          1635: .HI bss segment,
        !          1636: occupied by static data that is
        !          1637: implicitly initialized to zero values
        !          1638: (the name comes from a 1950's assembler), and
        !          1639: (iv) the
        !          1640: .HI stack segment,
        !          1641: occupied by
        !          1642: .C automatic
        !          1643: data, see
        !          1644: .C stack;
        !          1645: sometimes (ii), (iii), and (iv) are collectively called data segments.
        !          1646: .H server\ 
        !          1647: 1.\&
        !          1648: a 
        !          1649: .C process,
        !          1650: usually permanent, that serves
        !          1651: .C clients
        !          1652: through a
        !          1653: .C mounted
        !          1654: interface, either a
        !          1655: .C stream
        !          1656: or a
        !          1657: .C special file system.
        !          1658: 2.\&
        !          1659: a program, often a server
        !          1660: [1],
        !          1661: accessed via a distinctive
        !          1662: network address to provide some
        !          1663: remote computing service.
        !          1664: .H set userid\ 
        !          1665: a special
        !          1666: .C permission
        !          1667: for an
        !          1668: .C executable file
        !          1669: [1] that causes a
        !          1670: .C process
        !          1671: executing it
        !          1672: to have the access rights of the
        !          1673: .C owner
        !          1674: of the file;
        !          1675: the owner's
        !          1676: .C userid
        !          1677: becomes the
        !          1678: .HI effective userid
        !          1679: of the process, distinguished from the
        !          1680: .HI real userid
        !          1681: under which the process began.
        !          1682: .HI set userid bit\ 
        !          1683: the associated
        !          1684: .C permission bit.
        !          1685: .H shared text\ 
        !          1686: a
        !          1687: .C text segment,
        !          1688: one copy of which may be used simultaneously by more than one
        !          1689: .C process.
        !          1690: .H shell\ 
        !          1691: 1.\&
        !          1692: the program
        !          1693: .I sh (1),
        !          1694: which causes other programs
        !          1695: to be executed on
        !          1696: .C command
        !          1697: [2];
        !          1698: the shell is usually started on a user's behalf upon
        !          1699: .C logging in.
        !          1700: 2.\&
        !          1701: by analogy, any program started upon logging in.
        !          1702: .H shell script, command file\ 
        !          1703: a
        !          1704: .C file
        !          1705: [2] of
        !          1706: .C commands
        !          1707: taken as input to the
        !          1708: .C shell
        !          1709: [1].
        !          1710: .H signal\ 
        !          1711: an exceptional occurrence that causes a
        !          1712: .C process
        !          1713: to terminate or divert from the normal flow of control; cf.\&
        !          1714: .C interrupt,
        !          1715: .C kill.
        !          1716: .H sleep\ 
        !          1717: to cease activity for a specified time, or until a
        !          1718: .C signal
        !          1719: occurs, said of a
        !          1720: .C process.
        !          1721: .H soft link\ 
        !          1722: same as
        !          1723: .C symbolic link.
        !          1724: .H spawn\ 
        !          1725: to cause a
        !          1726: .C program
        !          1727: to be run in a 
        !          1728: .C child process;
        !          1729: cf.\&
        !          1730: .C fork, execute.
        !          1731: .H special character\ 
        !          1732: a character, which, when typed
        !          1733: at a terminal, modifies the input or affects the behavior of
        !          1734: .C processes
        !          1735: for which that terminal is the
        !          1736: .C control terminal;
        !          1737: examples are the
        !          1738: .C interrupt character,
        !          1739: .C erase character,
        !          1740: and
        !          1741: .C EOT character.
        !          1742: .H special file\ 
        !          1743: an
        !          1744: .C inode
        !          1745: that designates a
        !          1746: .C device,
        !          1747: further categorized as either
        !          1748: (i) a
        !          1749: .HI block special file
        !          1750: describing a
        !          1751: .C block device,
        !          1752: or (ii) a
        !          1753: .HI character special file
        !          1754: describing a
        !          1755: .C character device.
        !          1756: .H special file system\ 
        !          1757: 1.\&
        !          1758: a virtual
        !          1759: .C directory,
        !          1760: in which
        !          1761: .C `entries'
        !          1762: are constructed as needed.
        !          1763: Examples are
        !          1764: .CW /n , 
        !          1765: the
        !          1766: .C network file system,
        !          1767: and
        !          1768: .CW /proc ,
        !          1769: the
        !          1770: .C process directory.
        !          1771: .H spool\ 
        !          1772: to collect and serialize output from multiple
        !          1773: .C processes
        !          1774: competing
        !          1775: for a single output service.
        !          1776: .HI spooler\ 
        !          1777: a
        !          1778: .C daemon
        !          1779: that spools.
        !          1780: .HI spool area\ 
        !          1781: a
        !          1782: .C directory
        !          1783: in which a
        !          1784: spooler collects work.
        !          1785: .H stack, stack segment\ 
        !          1786: a
        !          1787: .C segment
        !          1788: of the address space into which
        !          1789: .C automatic
        !          1790: data and subroutine linkage information is allocated in
        !          1791: last-in-first-out fashion;
        !          1792: the stack occupies the largest data addresses and grows downward
        !          1793: towards
        !          1794: .C static
        !          1795: data.
        !          1796: .H standard input, standard output, standard error\ 
        !          1797: .C open files,
        !          1798: customarily available when a
        !          1799: .C process
        !          1800: begins, with
        !          1801: .C file descriptors
        !          1802: 0, 1, 2 and
        !          1803: .C stdio
        !          1804: names
        !          1805: .CW stdin ,
        !          1806: .CW stdout ,
        !          1807: .CW stderr .
        !          1808: Where possible, utilities by default read from the
        !          1809: standard input, write on the standard output, and place
        !          1810: error comments on the standard error file.
        !          1811: .H standard input-output\ 
        !          1812: see
        !          1813: .C stdio.
        !          1814: .H start/stop protocol, XON-XOFF protocol\ 
        !          1815: a communication flow-control method in which a received
        !          1816: .C special character,
        !          1817: the
        !          1818: .HI stop character,
        !          1819: causes output to be suspended, and a received
        !          1820: .HI start character
        !          1821: causes output to be resumed.
        !          1822: The default start and stop characters are ASCII DC1 (octal 022, control-Q)
        !          1823: and DC3 (octal 024, control S) respectively.
        !          1824: .H static\ 
        !          1825: persistent throughout a process,
        !          1826: said of data;
        !          1827: static data occupies the
        !          1828: .C data segment
        !          1829: and the
        !          1830: .C bss segment;
        !          1831: cf.\&
        !          1832: .C automatic.
        !          1833: .H status\ 
        !          1834: see
        !          1835: .C exit status.
        !          1836: .H stdio, standard input-output\ 
        !          1837: a collection of functions for formatted and character-by-character
        !          1838: input-output at a higher level than the basic
        !          1839: .I read (2),
        !          1840: .I write,
        !          1841: and
        !          1842: .I open (2)
        !          1843: operations.
        !          1844: .H stream\ 
        !          1845: 1.\&
        !          1846: an
        !          1847: .C open file
        !          1848: with
        !          1849: .C buffering
        !          1850: superimposed by the
        !          1851: .C stdio
        !          1852: package.
        !          1853: 2.\&
        !          1854: a bidirectional input-output connection between a
        !          1855: .C process
        !          1856: and a
        !          1857: .C character device
        !          1858: or another process.
        !          1859: .H strip\ 
        !          1860: remove the
        !          1861: .C symbol table
        !          1862: and
        !          1863: .C relocation bits
        !          1864: from an
        !          1865: .C executable file
        !          1866: [1].
        !          1867: .H subdirectory\ 
        !          1868: a
        !          1869: .C directory
        !          1870: that appears as an
        !          1871: .C entry
        !          1872: [1] in another.
        !          1873: .H subshell\ 
        !          1874: another copy of the
        !          1875: .C shell
        !          1876: [1], with its own
        !          1877: .C environment
        !          1878: and 
        !          1879: .C open files,
        !          1880: run as a 
        !          1881: .C child process
        !          1882: of the shell;
        !          1883: .C shell scripts
        !          1884: and commands subject to 
        !          1885: .CW for
        !          1886: and
        !          1887: .CW while
        !          1888: or
        !          1889: enclosed in parentheses 
        !          1890: .CW ()
        !          1891: are normally run by subshells.
        !          1892: .H super-block\ 
        !          1893: the second
        !          1894: .C block
        !          1895: in a
        !          1896: .C file system
        !          1897: [1],
        !          1898: which describes the allocation of space in the file system; cf.\&
        !          1899: .C boot block.
        !          1900: .H super-user\ 
        !          1901: .C userid
        !          1902: 0, which can access any
        !          1903: .C file
        !          1904: [2] regardless of
        !          1905: .C permissions
        !          1906: and can perform privileged
        !          1907: .C system calls,
        !          1908: e.g. to set the clock.
        !          1909: .H swap\ 
        !          1910: to move the
        !          1911: .C core image
        !          1912: of an executing program between main and secondary store to
        !          1913: make room for other
        !          1914: .C processes.
        !          1915: .H swap area\ 
        !          1916: the part of secondary store to which
        !          1917: .C core images
        !          1918: are
        !          1919: .C swapped;
        !          1920: the swap area is disjoint from 
        !          1921: .C file systems
        !          1922: [1].
        !          1923: .H symbolic link\ 
        !          1924: an
        !          1925: .C inode
        !          1926: that contains the
        !          1927: .C pathname
        !          1928: of another.
        !          1929: References to the symbolic link become references to
        !          1930: the named inode.
        !          1931: .H symbol table\ 
        !          1932: information in an
        !          1933: .C object file
        !          1934: about the names
        !          1935: of data and functions in that file;
        !          1936: the symbol table and
        !          1937: .C relocation bits
        !          1938: are used by the
        !          1939: .C link editor
        !          1940: and by debuggers.
        !          1941: .H system call\ 
        !          1942: a basic operation performed by the
        !          1943: .C kernel;
        !          1944: see
        !          1945: .I intro (2).
        !          1946: .H system time\ 
        !          1947: the accumulated time spent by a
        !          1948: .C process
        !          1949: in
        !          1950: .C kernel
        !          1951: code; cf.\&
        !          1952: .C user time.
        !          1953: .H tandem\ 
        !          1954: a mode of the
        !          1955: .C terminal line discipline
        !          1956: in which the computer uses
        !          1957: .C start/stop protocol
        !          1958: to regulate data flow from another terminal or other computer.
        !          1959: .H terminal line discipline, teletype line discipline\ 
        !          1960: a
        !          1961: .C line discipline
        !          1962: that implements input-output features such as
        !          1963: .C erase character
        !          1964: and
        !          1965: .C raw mode;
        !          1966: see
        !          1967: .I ttyld (4).
        !          1968: .H terminal process\ 
        !          1969: a program downloaded into a 
        !          1970: .C layer,
        !          1971: often in collaboration with a
        !          1972: .C host process.
        !          1973: Running in a different environment, a
        !          1974: terminal process is not a UNIX
        !          1975: .C process.
        !          1976: .H text\ 
        !          1977: see
        !          1978: .C text file,
        !          1979: .C segment.
        !          1980: .H text file, ASCII file\ 
        !          1981: a
        !          1982: .C file,
        !          1983: the bytes of which are understood to be in
        !          1984: ASCII
        !          1985: code.
        !          1986: .H text segment\ 
        !          1987: see
        !          1988: .C segment.
        !          1989: .H time\ 
        !          1990: the number of seconds since the
        !          1991: .HI epoch\fR,
        !          1992: 00:00:00 Greenwich Mean Time, January 1, 1970.
        !          1993: .H u-area\ 
        !          1994: a collection of data about, but not in the address space of, a
        !          1995: .C process;
        !          1996: the u-area is kept with the
        !          1997: .C core image
        !          1998: of the process.
        !          1999: .H uid\ 
        !          2000: see
        !          2001: .C userid.
        !          2002: .H umask\ 
        !          2003: a list of
        !          2004: .C permissions
        !          2005: that will be denied for files
        !          2006: .C created
        !          2007: by a
        !          2008: .C process,
        !          2009: so called because the list is expressed as a
        !          2010: .C mode
        !          2011: bit mask.
        !          2012: .H UNIX\ 
        !          2013: the name of a family of systems software,
        !          2014: not an acronym for anything;
        !          2015: a registered trademark of AT&T, the word should be used
        !          2016: as an adjective, e.g. `UNIX system' or `UNIX software'.
        !          2017: Major genera are the
        !          2018: research versions issued as numbered `editions', the
        !          2019: Berkeley software distributions (BSD), and the commercial
        !          2020: System V.
        !          2021: .H unlink\ 
        !          2022: to remove an
        !          2023: .C entry
        !          2024: [1] from a
        !          2025: .C directory;
        !          2026: converse to
        !          2027: .C link
        !          2028: and
        !          2029: .C create.
        !          2030: .H upas\ 
        !          2031: 1.\&
        !          2032: a fabulous Javanese tree that poisoned everything
        !          2033: for miles around.
        !          2034: 2.\&
        !          2035: a routing and delivery system for electronic mail.
        !          2036: .H URP\ 
        !          2037: universal receiver protocol used by
        !          2038: .C Datakit.
        !          2039: .H usenet\ 
        !          2040: an informal, nationwide computer network based on
        !          2041: .I uucp (1),
        !          2042: over which
        !          2043: `netnews'
        !          2044: is distributed; see
        !          2045: .I readnews (7).
        !          2046: .H user code\ 
        !          2047: code that runs in a 
        !          2048: .C process,
        !          2049: as distinct from
        !          2050: .C kernel
        !          2051: code.
        !          2052: .H userid, uid\ 
        !          2053: an integer value, usually associated with a
        !          2054: .C login name;
        !          2055: the userid of a
        !          2056: .C process
        !          2057: becomes the
        !          2058: .C owner
        !          2059: of files
        !          2060: .C created
        !          2061: by the process; it is inherited
        !          2062: across
        !          2063: .C fork.
        !          2064: .H user space, user address space\ 
        !          2065: the address space of a 
        !          2066: .C process, 
        !          2067: as distinct from
        !          2068: .C kernel space.
        !          2069: The address spaces of different processes are
        !          2070: mutually disjoint.
        !          2071: .H user time\ 
        !          2072: the accumulated time spent by a
        !          2073: .C process
        !          2074: in
        !          2075: .C user code;
        !          2076: cf.\&
        !          2077: .C system time.
        !          2078: .H utility, utility program\ 
        !          2079: a standard, generally useful, permanently available
        !          2080: .C program;
        !          2081: utilities normally inhabit directories
        !          2082: .CW /bin
        !          2083: and
        !          2084: .CW /usr/bin .
        !          2085: .H wait\ 
        !          2086: to suspend running until the termination of another
        !          2087: .C process;
        !          2088: only a
        !          2089: .C parent process
        !          2090: can wait for one of its
        !          2091: .C child processes.
        !          2092: .H window\ 
        !          2093: 1.\&
        !          2094: same as
        !          2095: .C layer.
        !          2096: 2.\&
        !          2097: a sublayer in
        !          2098: .C terminal processes
        !          2099: such as
        !          2100: .I pi (9)
        !          2101: or
        !          2102: .I sam (9).
        !          2103: .H working directory\ 
        !          2104: same as
        !          2105: .C current directory.
        !          2106: .H write behind\ 
        !          2107: to 
        !          2108: .C buffer
        !          2109: data for writing to a
        !          2110: .C device
        !          2111: [2] at a convenient time without holding up the computation
        !          2112: of a writing 
        !          2113: .C process.
        !          2114: .H write pointer\ 
        !          2115: same as
        !          2116: .C file pointer.
        !          2117: .H XON-XOFF protocol\ 
        !          2118: same as
        !          2119: .C start/stop protocol.
        !          2120: .H zombie\ 
        !          2121: a terminated
        !          2122: .C process
        !          2123: with a running 
        !          2124: .C parent process
        !          2125: that has not 
        !          2126: .C waited
        !          2127: for it.

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