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1.1 root 1: .\" Copyright (c) 1980 Regents of the University of California.
2: .\" All rights reserved. The Berkeley software License Agreement
3: .\" specifies the terms and conditions for redistribution.
4: .\"
5: .\" @(#)pumanA.n 6.2 (Berkeley) 5/7/86
6: .\"
7: .if !\n(xx \{\
8: .so tmac.p \}
9: .ND
10: .nr H1 0
11: .af H1 A
12: .NH
13: Appendix to Wirth's Pascal Report
14: .PP
15: This section is an appendix to
16: the definition of the Pascal language in Niklaus Wirth's
17: .I "Pascal Report"
18: and, with that Report, precisely defines the
19: Berkeley
20: implementation.
21: This appendix includes a summary of extensions to the language,
22: gives the ways in which the undefined specifications were resolved,
23: gives limitations and restrictions of the current implementation,
24: and lists the added functions and procedures available.
25: It concludes with a list of differences with the commonly available
26: Pascal 6000\-3.4 implementation,
27: and some comments on standard and portable Pascal.
28: .NH 2
29: Extensions to the language Pascal
30: .PP
31: This section defines non-standard language constructs available in
32: .UP .
33: The
34: .B s
35: standard Pascal option of the translators
36: .PI
37: and
38: .PC
39: can be used to detect these extensions in programs which are to be transported.
40: .SH
41: String padding
42: .PP
43: .UP
44: will pad constant strings with blanks in expressions and as
45: value parameters to make them as long as is required.
46: The following is a legal
47: .UP
48: program:
49: .LS
50: \*bprogram\fP x(output);
51: \*bvar\fP z : \*bpacked\fP \*barray\fP [ 1 .. 13 ] \*bof\fP char;
52: \*bbegin\fP
53: z := 'red';
54: writeln(z)
55: \*bend\fP;
56: .LE
57: The padded blanks are added on the right.
58: Thus the assignment above is equivalent to:
59: .LS
60: z := 'red '
61: .LE
62: which is standard Pascal.
63: .SH
64: Octal constants, octal and hexadecimal write
65: .PP
66: Octal constants may be given as a sequence of octal digits followed
67: by the character `b' or `B'.
68: The forms
69: .LS
70: write(a:n \*boct\fP)
71: .LE
72: and
73: .LS
74: write(a:n \*bhex\fP)
75: .LE
76: cause the internal representation of
77: expression
78: .I a,
79: which must be Boolean, character, integer, pointer, or a user-defined enumerated
80: type,
81: to be written in octal or hexadecimal respectively.
82: .SH
83: Assert statement
84: .PP
85: An
86: .B assert
87: statement causes a
88: .I Boolean
89: expression to be evaluated
90: each time the statement is executed.
91: A runtime error results if any of the expressions evaluates to be
92: .I false .
93: The
94: .B assert
95: statement is treated as a comment if run-time tests are disabled.
96: The syntax for
97: .B assert
98: is:
99: .LS
100: \*bassert\fP <expr>
101: .LE
102: .SH
103: Enumerated type input-output
104: .PP
105: Enumerated types may be read and written.
106: On output the string name associated with the enumerated
107: value is output.
108: If the value is out of range,
109: a runtime error occurs.
110: On input an identifier is read and looked up
111: in a table of names associated with the
112: type of the variable, and
113: the appropriate internal value is assigned to the variable being
114: read.
115: If the name is not found in the table
116: a runtime error occurs.
117: .SH
118: Structure returning functions
119: .PP
120: An extension has been added which allows functions
121: to return arbitrary sized structures rather than just
122: scalars as in the standard.
123: .SH
124: Separate compilation
125: .PP
126: The compiler
127: .PC
128: has been extended to allow separate compilation of programs.
129: Procedures and functions declared at the global level
130: may be compiled separately.
131: Type checking of calls to separately compiled routines is performed
132: at load time to insure that the program as a whole
133: is consistent.
134: See section 5.10 for details.
135: .NH 2
136: Resolution of the undefined specifications
137: .SH
138: File name \- file variable associations
139: .PP
140: Each Pascal file variable is associated with a named
141: .UX
142: file.
143: Except for
144: .I input
145: and
146: .I output,
147: which are
148: exceptions to some of the rules, a name can become associated
149: with a file in any of three ways:
150: .IP "\ \ \ \ \ 1)" 10
151: If a global Pascal file variable appears in the
152: .B program
153: statement
154: then it is associated with
155: .UX
156: file of the same name.
157: .IP "\ \ \ \ \ 2)"
158: If a file was reset or rewritten using the
159: extended two-argument form of
160: .I reset
161: or
162: .I rewrite
163: then the given name
164: is associated.
165: .IP "\ \ \ \ \ 3)"
166: If a file which has never had
167: .UX
168: name associated
169: is reset or rewritten without specifying a name
170: via the second argument, then a temporary name
171: of the form `tmp.x'
172: is associated with the file.
173: Temporary names start with
174: `tmp.1' and continue by incrementing the last character in the
175: .SM
176: USASCII
177: .NL
178: ordering.
179: Temporary files are removed automatically
180: when their scope is exited.
181: .SH
182: The program statement
183: .PP
184: The syntax of the
185: .B program
186: statement is:
187: .LS
188: \*bprogram\fP <id> ( <file id> { , <file id > } ) ;
189: .LE
190: The file identifiers (other than
191: .I input
192: and
193: .I output )
194: must be declared as variables of
195: .B file
196: type in the global declaration part.
197: .SH
198: The files input and output
199: .PP
200: The formal parameters
201: .I input
202: and
203: .I output
204: are associated with the
205: .UX
206: standard input and output and have a
207: somewhat special status.
208: The following rules must be noted:
209: .IP "\ \ \ \ \ 1)" 10
210: The program heading
211: .B must
212: contains the formal parameter
213: .I output.
214: If
215: .I input
216: is used, explicitly or implicitly, then it must
217: also be declared here.
218: .IP "\ \ \ \ \ 2)"
219: Unlike all other files, the
220: Pascal files
221: .I input
222: and
223: .I output
224: must not be defined in a declaration,
225: as their declaration is automatically:
226: .LS
227: \*bvar\fP input, output: text
228: .LE
229: .IP "\ \ \ \ \ 3)"
230: The procedure
231: .I reset
232: may be used on
233: .I input.
234: If no
235: .UX
236: file name has ever been associated with
237: .I input,
238: and no file name is given, then an attempt will be made
239: to `rewind'
240: .I input.
241: If this fails, a run time
242: error will occur.
243: .I Rewrite
244: calls to output act as for any other file, except that
245: .I output
246: initially has no associated file.
247: This means that a simple
248: .LS
249: rewrite(output)
250: .LE
251: associates a temporary name with
252: .I output.
253: .SH
254: Details for files
255: .PP
256: If a file other than
257: .I input
258: is to be read,
259: then reading must be initiated by a call to the
260: procedure
261: .I reset
262: which causes the Pascal system to attempt to open the
263: associated
264: .UX
265: file for reading.
266: If this fails, then a runtime error occurs.
267: Writing of a file other than
268: .I output
269: must be initiated by a
270: .I rewrite
271: call,
272: which causes the Pascal system to create the associated
273: .UX
274: file and
275: to then open the file for writing only.
276: .SH
277: Buffering
278: .PP
279: The buffering for
280: .I output
281: is determined by the value of the
282: .B b
283: option
284: at the end of the
285: .B program
286: statement.
287: If it has its default value 1,
288: then
289: .I output
290: is
291: buffered in blocks of up to 512 characters,
292: flushed whenever a writeln occurs
293: and at each reference to the file
294: .I input.
295: If it has the value 0,
296: .I output
297: is unbuffered.
298: Any value of
299: 2 or more gives block buffering without line or
300: .I input
301: reference flushing.
302: All other output files are always buffered in blocks of 512 characters.
303: All output buffers are flushed when the files are closed at scope exit,
304: whenever the procedure
305: .I message
306: is called, and can be flushed using the
307: built-in procedure
308: .I flush.
309: .PP
310: An important point for an interactive implementation is the definition
311: of `input\(ua'.
312: If
313: .I input
314: is a teletype, and the Pascal system reads a character at the beginning
315: of execution to define `input\(ua', then no prompt could be printed
316: by the program before the user is required to type some input.
317: For this reason, `input\(ua' is not defined by the system until its definition
318: is needed, reading from a file occurring only when necessary.
319: .SH
320: The character set
321: .PP
322: Seven bit
323: .SM USASCII
324: is the character set used on
325: .UX .
326: The standard Pascal
327: symbols `and', 'or', 'not', '<=', '>=', '<>',
328: and the uparrow `\(ua' (for pointer qualification)
329: are recognized.\*(dg
330: .FS
331: \*(dgOn many terminals and printers, the up arrow is represented
332: as a circumflex `^'.
333: These are not distinct characters, but rather different graphic
334: representations of the same internal codes.
335: .FE
336: Less portable are the
337: synonyms tilde `~'
338: for
339: .B not ,
340: `&' for
341: .B and ,
342: and `|' for
343: .B or .
344: .PP
345: Upper and lower case are considered to be distinct.\*(st
346: .FS
347: \*(stThe proposed standard for Pascal considers them to be the same.
348: .FE
349: Keywords and built-in
350: .B procedure
351: and
352: .B function
353: names are
354: composed of all lower case letters.
355: Thus the identifiers GOTO and GOto are distinct both from each other and
356: from the keyword
357: \*bgoto\fP.
358: The standard type `boolean' is also available as `Boolean'.
359: .PP
360: Character strings and constants may be delimited by the character
361: `\''
362: or by the character `#';
363: the latter is sometimes convenient when programs are to be transported.
364: Note that the `#' character has special meaning
365: .up
366: when it is the first character on a line \- see
367: .I "Multi-file programs"
368: below.
369: .SH
370: The standard types
371: .PP
372: The standard type
373: .I integer
374: is conceptually defined as
375: .LS
376: \*btype\fP integer = minint .. maxint;
377: .LE
378: .I Integer
379: is implemented with 32 bit twos complement arithmetic.
380: Predefined constants of type
381: .I integer
382: are:
383: .LS
384: \*bconst\fP maxint = 2147483647; minint = -2147483648;
385: .LE
386: .PP
387: The standard type
388: .I char
389: is conceptually defined as
390: .LS
391: \*btype\fP char = minchar .. maxchar;
392: .LE
393: Built-in character constants are `minchar' and `maxchar', `bell' and `tab';
394: ord(minchar) = 0, ord(maxchar) = 127.
395: .PP
396: The type
397: .I real
398: is implemented using 64 bit floating point arithmetic.
399: The floating point arithmetic is done in `rounded' mode, and
400: provides approximately 17 digits of precision
401: with numbers as small as 10 to the negative 38th power and as large as
402: 10 to the 38th power.
403: .SH
404: Comments
405: .PP
406: Comments can be delimited by either `{' and `}' or by `(*' and `*)'.
407: If the character `{' appears in a comment delimited by `{' and `}',
408: a warning diagnostic is printed.
409: A similar warning will be printed if the sequence `(*' appears in
410: a comment delimited by `(*' and `*)'.
411: The restriction implied by this warning is not part of standard Pascal,
412: but detects many otherwise subtle errors.
413: .SH
414: Option control
415: .PP
416: Options of the translators may be controlled
417: in two distinct ways.
418: A number of options may appear on the command line invoking the translator.
419: These options are given as one or more strings of letters preceded by the
420: character `\-' and cause the default setting of
421: each given option to be changed.
422: This method of communication of options is expected to predominate
423: for
424: .UX .
425: Thus the command
426: .LS
427: % \*bpi \-l \-s foo.p\fR
428: .LE
429: translates the file foo.p with the listing option enabled (as it normally
430: is off), and with only standard Pascal features available.
431: .PP
432: If more control over the portions of the program where options are enabled is
433: required, then option control in comments can and should be used.
434: The
435: format for option control in comments is identical to that used in Pascal
436: 6000\-3.4.
437: One places the character `$' as the first character of the comment
438: and follows it by a comma separated list of directives.
439: Thus an equivalent to the command line example given above would be:
440: .LS
441: {$l+,s+ listing on, standard Pascal}
442: .LE
443: as the first line of the program.
444: The `l'
445: option is more appropriately specified on the command line,
446: since it is extremely unlikely in an interactive environment
447: that one wants a listing of the program each time it is translated.
448: .PP
449: Directives consist of a letter designating the option,
450: followed either by a `+' to turn the option on, or by a `\-' to turn the
451: option off.
452: The
453: .B b
454: option takes a single digit instead of
455: a `+' or `\-'.
456: .SH
457: Notes on the listings
458: .PP
459: The first page of a listing
460: includes a banner line indicating the version and date of generation of
461: .PI
462: or
463: .PC .
464: It also
465: includes the
466: .UX
467: path name supplied for the source file and the date of
468: last modification of that file.
469: .PP
470: Within the body of the listing, lines are numbered consecutively and
471: correspond to the line numbers for the editor.
472: Currently, two special
473: kinds of lines may be used to format the listing:
474: a line consisting of a form-feed
475: character, control-l, which causes a page
476: eject in the listing, and a line with
477: no characters which causes the line number to be suppressed in the listing,
478: creating a truly blank line.
479: These lines thus correspond to `eject' and `space' macros found in many
480: assemblers.
481: Non-printing characters are printed as the character `?' in the listing.\*(dg
482: .FS
483: \*(dgThe character generated by a control-i indents
484: to the next `tab stop'.
485: Tab stops are set every 8 columns in
486: .UX .
487: Tabs thus provide a quick way of indenting in the program.
488: .FE
489: .SH
490: The standard procedure write
491: .PP
492: If no minimum field length parameter is specified
493: for a
494: .I write,
495: the following default
496: values are assumed:
497: .KS
498: .TS
499: center;
500: l n.
501: integer 10
502: real 22
503: Boolean length of `true' or `false'
504: char 1
505: string length of the string
506: oct 11
507: hex 8
508: .TE
509: .KE
510: The end of each line in a text file should be explicitly
511: indicated by `writeln(f)', where `writeln(output)' may be written
512: simply as `writeln'.
513: For
514: .UX ,
515: the built-in function `page(f)' puts a single
516: .SM ASCII
517: form-feed character on the output file.
518: For programs which are to be transported the filter
519: .I pcc
520: can be used to interpret carriage control, as
521: .UX
522: does not normally do so.
523: .NH 2
524: Restrictions and limitations
525: .SH
526: Files
527: .PP
528: Files cannot be members of files or members of dynamically
529: allocated structures.
530: .SH
531: Arrays, sets and strings
532: .PP
533: The calculations involving array subscripts and set elements
534: are done with 16 bit arithmetic.
535: This
536: restricts the types over which arrays and sets may be defined.
537: The lower bound of such a range must be greater than or equal to
538: \-32768, and the upper bound less than 32768.
539: In particular, strings may have any length from 1 to 65535 characters,
540: and sets may contain no more than 65535 elements.
541: .SH
542: Line and symbol length
543: .PP
544: There is no intrinsic limit on the length of identifiers.
545: Identifiers
546: are considered to be distinct if they differ
547: in any single position over their entire length.
548: There is a limit, however, on the maximum input
549: line length.
550: This limit is quite generous however, currently exceeding 160
551: characters.
552: .SH
553: Procedure and function nesting and program size
554: .PP
555: At most 20 levels of
556: .B procedure
557: and
558: .B function
559: nesting are allowed.
560: There is no fundamental, translator defined limit on the size of the
561: program which can be translated.
562: The ultimate limit is supplied by the
563: hardware and thus, on the \s-2PDP\s0-11,
564: by the 16 bit address space.
565: If
566: one runs up against the `ran out of memory' diagnostic the program may yet
567: translate if smaller procedures are used, as a lot of space is freed
568: by the translator at the completion of each
569: .B procedure
570: or
571: .B function
572: in the current
573: implementation.
574: .PP
575: On the \s-2VAX\s0-11, there is an implementation defined limit
576: of 65536 bytes per variable.
577: There is no limit on the number of variables.
578: .SH
579: Overflow
580: .PP
581: There is currently no checking for overflow on arithmetic operations at
582: run-time on the \s-2PDP\s0-11.
583: Overflow checking is performed on the \s-2VAX\s0-11 by the hardware.
584: .br
585: .ne 15
586: .NH 2
587: Added types, operators, procedures and functions
588: .SH
589: Additional predefined types
590: .PP
591: The type
592: .I alfa
593: is predefined as:
594: .LS
595: \*btype\fP alfa = \*bpacked\fP \*barray\fP [ 1..10 ] \*bof\fP \*bchar\fP
596: .LE
597: .PP
598: The type
599: .I intset
600: is predefined as:
601: .LS
602: \*btype\fP intset = \*bset of\fP 0..127
603: .LE
604: In most cases the context of an expression involving a constant
605: set allows the translator to determine the type of the set, even though the
606: constant set itself may not uniquely determine this type.
607: In the
608: cases where it is not possible to determine the type of the set from
609: local context, the expression type defaults to a set over the entire base
610: type unless the base type is integer\*(dg.
611: .FS
612: \*(dgThe current translator makes a special case of the construct
613: `if ... in [ ... ]' and enforces only the more lax restriction
614: on 16 bit arithmetic given above in this case.
615: .FE
616: In the latter case the type defaults to the current
617: binding of
618: .I intset,
619: which must be ``type set of (a subrange of) integer'' at that point.
620: .PP
621: Note that if
622: .I intset
623: is redefined via:
624: .LS
625: \*btype\fP intset = \*bset of\fP 0..58;
626: .LE
627: then the default integer set is the implicit
628: .I intset
629: of
630: Pascal 6000\-3.4
631: .SH
632: Additional predefined operators
633: .PP
634: The relationals `<' and `>' of proper set
635: inclusion are available.
636: With
637: .I a
638: and
639: .I b
640: sets, note that
641: .LS
642: (\*bnot\fR (\fIa\fR < \fIb\fR)) <> (\fIa\fR >= \fIb\fR)
643: .LE
644: As an example consider the sets
645: .I a
646: = [0,2]
647: and
648: .I b
649: = [1].
650: The only relation true between these sets is `<>'.
651: .SH
652: Non-standard procedures
653: .IP argv(i,a) 25
654: where
655: .I i
656: is an integer and
657: .I a
658: is a string variable
659: assigns the (possibly truncated or blank padded)
660: .I i \|'th
661: argument
662: of the invocation of the current
663: .UX
664: process to the variable
665: .I a .
666: The range of valid
667: .I i
668: is
669: .I 0
670: to
671: .I argc\-1 .
672: .IP date(a)
673: assigns the current date to the alfa variable
674: .I a
675: in the format `dd mmm yy ', where `mmm' is the first
676: three characters of the month, i.e. `Apr'.
677: .IP flush(f)
678: writes the output buffered for Pascal file
679: .I f
680: into the associated
681: .UX
682: file.
683: .IP halt
684: terminates the execution of the program with
685: a control flow backtrace.
686: .IP linelimit(f,x)\*(dd
687: .FS
688: \*(ddCurrently ignored by pdp-11
689: .X .
690: .FE
691: with
692: .I f
693: a textfile and
694: .I x
695: an integer expression
696: causes
697: the program to be abnormally terminated if more than
698: .I x
699: lines are
700: written on file
701: .I f .
702: If
703: .I x
704: is less than 0 then no limit is imposed.
705: .IP message(x,...)
706: causes the parameters, which have the format of those
707: to the
708: built-in
709: .B procedure
710: .I write,
711: to be written unbuffered on the diagnostic unit 2,
712: almost always the user's terminal.
713: .IP null
714: a procedure of no arguments which does absolutely nothing.
715: It is useful as a place holder,
716: and is generated by
717: .XP
718: in place of the invisible empty statement.
719: .IP remove(a)
720: where
721: .I a
722: is a string causes the
723: .UX
724: file whose
725: name is
726: .I a,
727: with trailing blanks eliminated, to be removed.
728: .IP reset(f,a)
729: where
730: .I a
731: is a string causes the file whose name
732: is
733: .I a
734: (with blanks trimmed) to be associated with
735: .I f
736: in addition
737: to the normal function of
738: .I reset.
739: .IP rewrite(f,a)
740: is analogous to `reset' above.
741: .IP stlimit(i)
742: where
743: .I i
744: is an integer sets the statement limit to be
745: .I i
746: statements.
747: Specifying the
748: .B p
749: option to
750: .I pc
751: disables statement limit counting.
752: .IP time(a)
753: causes the current time in the form `\ hh:mm:ss\ ' to be
754: assigned to the alfa variable
755: .I a.
756: .SH
757: Non-standard functions
758: .IP argc 25
759: returns the count of arguments when the Pascal program
760: was invoked.
761: .I Argc
762: is always at least 1.
763: .IP card(x)
764: returns the cardinality of the set
765: .I x,
766: i.e. the
767: number of elements contained in the set.
768: .IP clock
769: returns an integer which is the number of central processor
770: milliseconds of user time used by this process.
771: .IP expo(x)
772: yields the integer valued exponent of the floating-point
773: representation of
774: .I x ;
775: expo(\fIx\fP) = entier(log2(abs(\fIx\fP))).
776: .IP random(x)
777: where
778: .I x
779: is a real parameter, evaluated but otherwise
780: ignored, invokes a linear congruential random number generator.
781: Successive seeds are generated as (seed*a + c) mod m and
782: the new random number is a normalization of the seed to the range 0.0 to 1.0;
783: a is 62605, c is 113218009, and m is
784: 536870912.
785: The initial seed
786: is 7774755.
787: .IP seed(i)
788: where
789: .I i
790: is an integer sets the random number generator seed
791: to
792: .I i
793: and returns the previous seed.
794: Thus seed(seed(i))
795: has no effect except to yield value
796: .I i.
797: .IP sysclock
798: an integer function of no arguments returns the number of central processor
799: milliseconds of system time used by this process.
800: .IP undefined(x)
801: a Boolean function.
802: Its argument is a real number and
803: it always returns false.
804: .IP wallclock
805: an integer function of no arguments returns the time
806: in seconds since 00:00:00 GMT January 1, 1970.
807: .NH 2
808: Remarks on standard and portable Pascal
809: .PP
810: It is occasionally desirable to prepare Pascal programs which will be
811: acceptable at other Pascal installations.
812: While certain system dependencies are bound to creep in,
813: judicious design and programming practice can usually eliminate
814: most of the non-portable usages.
815: Wirth's
816: .I "Pascal Report"
817: concludes with a standard for implementation and program exchange.
818: .PP
819: In particular, the following differences may cause trouble when attempting
820: to transport programs between this implementation and Pascal 6000\-3.4.
821: Using the
822: .B s
823: translator option may serve to indicate many problem areas.\*(dg
824: .FS
825: \*(dgThe
826: .B s
827: option does not, however, check that identifiers differ
828: in the first 8 characters.
829: .I Pi
830: and
831: .PC
832: also do not check the semantics of
833: .B packed .
834: .FE
835: .SH
836: Features not available in Berkeley Pascal
837: .IP
838: Segmented files and associated functions and procedures.
839: .IP
840: The function
841: .I trunc
842: with two arguments.
843: .IP
844: Arrays whose indices exceed the capacity of 16 bit arithmetic.
845: .SH
846: Features available in Berkeley Pascal but not in Pascal 6000-3.4
847: .IP
848: The procedures
849: .I reset
850: and
851: .I rewrite
852: with file names.
853: .IP
854: The functions
855: .I argc,
856: .I seed,
857: .I sysclock,
858: and
859: .I wallclock.
860: .IP
861: The procedures
862: .I argv,
863: .I flush,
864: and
865: .I remove.
866: .IP
867: .I Message
868: with arguments other than character strings.
869: .IP
870: .I Write
871: with keyword
872: .B hex .
873: .IP
874: The
875: .B assert
876: statement.
877: .IP
878: Reading and writing of enumerated types.
879: .IP
880: Allowing functions to return structures.
881: .IP
882: Separate compilation of programs.
883: .IP
884: Comparison of records.
885: .SH
886: Other problem areas
887: .PP
888: Sets and strings are more general in \*
889: .UP ;
890: see the restrictions given in
891: the
892: Jensen-Wirth
893: .I "User Manual"
894: for details on the 6000\-3.4 restrictions.
895: .PP
896: The character set differences may cause problems,
897: especially the use of the function
898: .I chr,
899: characters as arguments to
900: .I ord,
901: and comparisons of characters,
902: since the character set ordering
903: differs between the two machines.
904: .PP
905: The Pascal 6000\-3.4 compiler uses a less strict notion of type equivalence.
906: In
907: .UP ,
908: types are considered identical only if they are represented
909: by the same type identifier.
910: Thus, in particular, unnamed types are unique
911: to the variables/fields declared with them.
912: .PP
913: Pascal 6000\-3.4 doesn't recognize our option
914: flags, so it is wise to
915: put the control of
916: .UP
917: options to the end of option lists or, better
918: yet, restrict the option list length to one.
919: .PP
920: For Pascal 6000\-3.4 the ordering of files in the program statement has
921: significance.
922: It is desirable to place
923: .I input
924: and
925: .I output
926: as the first two files in the
927: .B program
928: statement.
929: .sp 2
930: .SH
931: Acknowledgments
932: .PP
933: The financial support of William Joy and Susan Graham by
934: the National Science Foundation under grants
935: MCS74-07644-A04, MCS78-07291, and MCS80-05144,
936: and the William Joy by an
937: .SM IBM
938: Graduate Fellowship are gratefully acknowledged.
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