Table Of ContentINTERNATIONAL ISOAEC
STANDARD 7185
Second edition
1990-10-15
Information technology - Programming
languages - Pascal
(Revision of IS0 7185 : 1983)
Technologies de l’information - Langages de programmation - Pascal
(RBvision de I’ISO 7185 : 1983)
Reference number
ISO/IEC 7185 : 1990 (E)
ISO,‘IEC 7185 : 1990 (E)
Contents
1 Scope ................
2 Normative reference .... . . . . . . . . . . . ....... 1
3 Definitions ............ . . . . . . . . . ....... 1
4 Definitional conventions . . . . . . . . . . . . . . . 2
5 Compliance ........... . . . . . . . . . ....... 3
5.1 Processors ....... . . ....... 3
5.2 Programs ........ . . . . . . . . . . ....... 5
6 Requirements ......... . . . . . . . . . . . . . . . . . . . 5
6.1 Lexicaltokens ........................ . . . . . . . . . . 5
6.2 Blocks, scopes and activations ......... . . . . . . . . 8
6.3 Constant - definitions ................. . . . . . 11
6.4 Type - definitions. .................... . . . 11
6.5 Declarations and denotations of variables . . . . 21
6.6 Procedure and function declarations .... 24
6.7 Expressions .......................... . . . . 38
6.8 Statements .......................... . . . . . . . . . . . . . . 42
6.9 Input and output ..................... . . . . . . . . . . . . 49
6.10 Programs ........................... . . . 55
A Collectedsyntax ..................................................... 58
B Cross-references .................................................... 64
C Required identifiers .................................................. 71
D Errors .............................................................. 72
E Implementation - defined features . . . . . . . . . . . . . 76
F Implementation - dependent features . . . . . . . 78
0 ISO/IEC 1990
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ii
ISO/IEC 7185 : 1990 (E)
Foreword
IS0 (the International Organization for Standardization) and IEC (the International
Electrotechnical Commission) form the specialized system for worldwide standardiz-
ation. National bodies that are members of IS0 or IEC participate in the development
of International Standards through technical committees established by the respective
organization to deal with particular fields of technical activity. IS0 and IEC technical
committees collaborate in fields of mutual interest. Other international organizations,
governmental and non-governmental, in liaison with IS0 and IEC, also take part in the
work.
In the field of information technology, IS0 and IEC have established a joint technical
committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint
technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting
a vote.
International Standard ISO/IEC 7185 was prepared by Joint Technical Committee
ISO/IEC JTC 1, Information technology.
This second edition cancels and replaces the first edition (IS0 7185 : 1983).
Annexes A, S, C, D, E and F are for information.
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ISO/IEC7185:1990(E)
Introduction
This International Standard provides an unambiguousa nd machine independentd efinition of the
programmingl anguageP ascal. Its purposei s to facilitate portability of Pascalp rogramsf or use on a
wide variety of datap rocessings ystems.
Language history
The computer programmingl anguageP ascal was designedb y ProfessorN iklaus Wirth to satisfy two
principal aims
a) to makea vailablea languages uitablef or teachingp rogramminga s a systematicd iscipline basedo n
certainf undamentalc onceptsc learly and naturally reflectedb y the language;
b) to define a languagew hosei mplementationsc ould be both reliable and efficient on then-available
computers.
However, it has becomea pparentt hat Pascalh as attributest hat go far beyond theseo riginal goals. It is
now being increasinglyu sed commerciallyi n the writing of both system and application software. This
InternationalS tandardi s primarily a consequenceo f the growing commerciali nterest in Pascala nd the
needt o promotet he portability of Pascalp rogramsb etweend atap rocessings ystems.
In drafting this International Standardt he continued stability of Pascal has been a prime objective.
However,a part from changest o clarify the specification,t wo major changesh aveb eeni ntroduced.
a) The syntax used to specify procedurala nd functional parametersh as beenc hangedt o require the
use of a procedureo r function heading,a s appropriate( see6 .6.3.1); this changew as introducedt o
overcomea languagei nsecurity.
b) A fifth kind of parameter,t he conformant-array-parametehra, sb eeni ntroduced( see6 .6.3.7). With
this kind of parameter,t he requiredb oundso f the index-typeo f an actual-parametear re not fixed,
but are restrictedt o a specifiedr angeo f values.
Project history
In 1977,a working group was formed within the British StandardsIn stitution (BSI) to producea standard
for the programmingl anguageP ascal.T his groupp roduceds everalw orking drafts, the first draft for public
commentb eing widely publishede arly in 1979. In 1978,B SI’s proposalt hat Pascalb e addedt o ISO’s
programo f work was accepteda, ndt he IS0 PascalW orking Group( thend esignatedIS O/TC97/SC5/WG4)
was formed in 1979. The Pascals tandardw as to be publishedb y BSI on behalf of ISO, and this British
Standardr eferencedb y the InternationalS tandard.
In the USA, in the fall of 1978,a pplicationw as madet o the IEEE StandardsB oardb y the IEEE Computer
Society to authorizep roject 770 (Pascal).A fter approval,t he first meetingw as held in January1 979.
In Decembero f 1978, X3J9 conveneda s a result of a SPARC (StandardsP lanning and Requirements
Committee)r esolution to form a US TAG (TechnicalA dvisory Group) for the IS0 Pascals tandardization
effort initiated by the UK. Thesee fforts were performedu nderX 3 project 317.
In agreementw ith IEEE representativesi,n Februaryo f 1979,a n X3 resolution combinedt he X3J9 and
P770c ommitteesi nto a single committeec alled the Joint X3J9/IEEE-P770P ascalS tandardsC ommittee.
(Throughout,t he term JPC refers to this committee.)T he first meetinga s JPC was held in April 1979.
The resolution to form JPC clarified the dual function of the singlej oint committeet o producea dpANS
and a proposedI EEE Pascals tandard,id entical in content.
ANSI/lEEE77OX3.97-1983A, merican National StandardP ascalC omputerP rogrammingL anguage,w as
approvedb y the IEEE StandardsB oard on September1 7,1981, and by the American National Standards
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ISO/IEC 7185:1990(E)
Institute on December 16, 1982. British StandardB S6192, Specification for Computerp rogramming
languageP ascal, was published in 1982, and International Standard7 185 (incorporatingB S6192 by
reference)w as approvedb y IS0 on December1 ,1983. Differencesb etweent he ANSI and IS0 standards
are detailedi n the Forewordo f ANSI/IEEE77OX3.97-1983.
In 1985,t he IS0 PascalW orking Group (then designatedI SO/TC97/SC22/WG2,n ow ISO/IEC JTCl/
SC22/WG2) was reconveneda fter a long break. An InterpretationsS ubgroupw as formed, to interpret
doubtful or ambiguousp ortions of the Pascals tandards.A s a result of the work of this subgroup,a nd also
of the work on the ExtendedP ascals tandardb eing producedb y WG2 and JPC, BS6192/IS07185w as
revised and correctedd uring 1988/89;i t is expectedt hat ANSI/IEEE770X3.97-1983w ill be replacedb y
the revisedI S0 7 185.
The major revisions to BS6192:1 982t o producet he new IS0 7 185a re:
a) resolutiono f the differencesw ith ANSI/IEEE77OX3.97-1983;
b) relaxationo f the syntax of real numbers,t o allow “digit sequencesr”a thert han “unsignedi ntegers”
for the variousc omponents;
c) in the handlingo f “end-of-linec haracters”i n text files;
d) in the handlingo f run-time errors.
V
INTERNATIONAL STANDARD ISOAEC 7185: 1990(E)
Information technology - Programming languages -
Pascal
1 Scope
1.1
This International Standards pecifiest he semanticsa nd syntax of the computerp rogrammingl anguage
Pascalb y specifyingr equirementsfo r a processora ndf or a conformingp rogram.T wo levels of compliance
are definedf or both processorsa nd programs.
1.2
This InternationalS tandardd oesn ot specify
a) the size or complexity of a programa nd its data that will exceedt he capacity of any specific data
processings ystem or the capacity of a particular processor,n or the actions to be taken when the
correspondingli mits are exceeded;
b) the minimal requirementso f a datap rocessings ystemt hat is capableo f supportinga n implementation
of a processorf or Pascal;
c) the methodo f activating the program-blocko r the set of commandsu sedt o control the environment
in which a Pascalp rogrami s transformeda nd executed;
d) the mechanismb y which programsw ritten in Pascala re transformedf or use by a data processing
system;
e) the methodf or reportinge rrorso r warnings;
f) the typographicalr epresentationo f a programp ublishedf or humanr eading.
2 Normative reference
The following standardc ontains provisions which, through referencei n this text, constitute provisions
of this InternationalS tandard.A t the time of publication, the edition indicated was valid. All standards
are subjectt o revision, and parties to agreementsb asedo n this International Standarda re encouragedto
investigatet he possibility of applying the most recent edition of the standardl isted below. Memberso f
IEC and IS0 maintainr egisterso f currently valid InternationalS tandards.
IS0 646:1 983,I nformation processing-IS0 7-bit codedc haracters etf or information interchange.
3 Definitions
For the purposeso f this InternationalS tandard,t he following definitions apply.
NOTE - To draw attention to language concepts, some terms are printed in italics on their fist mention or at their
defining occurrence(s) in this International Standard.
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ISO/IEC 7185:1990(E)
3.1 Error
A violation by a programo f the requirementso f this InternationalS tandardt hat a processori s permitted
to leaveu ndetected.
NOTES
1 If it is possible to construct a program in which the violation or non-violation of this International Standard requires
knowledge of the data read by the program or the implementation definition of implementation-defined features, then
violation of that requirement is classified as an error. Processors may report on such violations of the requirement
without such knowledge, but there always remain some cases that require execution, simulated execution, or proof
procedures with the required knowledge. Requirements that can be verified without such knowledge are not classitied
as errors.
2 Processors should attempt the detection of as many errors as possible, and to as complete a degree as possible.
Permission to omit detection is provided for implementations in which the detection would be an excessive burden.
3.2 Extension
A modification to clause6 of the requirementso f this InternationalS tandardt hat doesn ot invalidate any
programc omplying with this InternationalS tandard,a s definedb y 5.2, exceptb y prohibiting the use of
one or morep articular spellingso f identifiers( see6 .1.2 and 6.13).
3.3 Implementation-defined
Possiblyd iffering betweenp rocessorsb, ut definedf or any particular processor.
3.4 Implementation-dependent
Possibly differing betweenp rocessorsa nd not necessarilyd efinedf or any particularp rocessor.
3.5 Processor
A systemo r mechanismt hat acceptsa programa s input, preparesit for execution,a nde xecutest he process
so definedw ith data to producer esults.
NOTE - A processor may consist of an interpreter, a compiler and run-time system, or another mechanism, together
with an associated host computing machine and operating system, or another mechanism for achieving the same effect.
A compiler in itself, for example, does not constitute a processor.
4 Definitional conventions
The me&languageu sed in this InternationalS tandardt o specify the syntax of the constructsi s basedo n
Backus-NaurF orm. The notation has beenm odified from the original to permit greaterc onvenienceo f
descriptiona nd to allow for iterative productionst o replacer ecursiveo nes. Table 1 lists the meaningso f
the various metasymbols.F urther specificationo f the constructsi s given by prosea nd, in somec ases,b y
equivalentp rogramf ragments.A ny identifier that is deEnedin clause6 as a requiredi dentifier shall denote
the correspondingre quirede ntity by its occurrencein sucha programf ragment. In all other respects,a ny
suchp rogramf ragmenti s boundb y any pertinentr equiremento f this InternationalS tandard.
A meta-identifiers hall be a sequenceo f letters and hyphensb eginningw ith a letter.
A sequenceo f terminala nd nonterminals ymbolsi n a productioni mplies the concatenationo f the text that
they ultimately represent.W ithin 6.1 this concatenationis direct; no characterss hall intervene.I n all other
parts of this InternationalS tandardt he concatenationis in accordancew ith the rules set out in 6.1.
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ISO/IEC 7185:1990(E)
Table 1 - Metalanguaee svmbols
Metasymbol Meaning
I Shall be definedt o be
> Shall have as an alternatived efinition
I Alternatively
End of definition
[xl 0 or 1 instanceo f x
(xl 0 or more instanceso f x
(xly) Grouping: either of x or y
‘xyz’ The terminal symbol xyz
me&identifier A nonterminals vmbol
The charactersr equiredt o form Pascalp rogramss hall be thosei mplicitly requiredt o form the tokens and
separatorsd efinedi n 6.1.
Use of the words of, in, containing, and closest-containing,w hen expressinga relationship between
terminal or nonterminals ymbols,s hall have the following meanings
-the x of a y: refers to the x occurring directly in a productiond efining y;
-the x in a y: is synonymousw ith ‘thex of a y’;
-a y containinga n x: refers to any y from which an x is directly or indirectly derived;
-the y closest-containinga n x: that y containing an x and not containing anothery containing that x.
These syntactic conventionsa re used in clause6 to specify certain syntactic requirementsa nd also the
contextsw ithin which certain semantics pecificationsa pply.
In addition to the normal English rules for hyphenation,h yphenationis usedi n this InternationalS tandard
to form compoundw ords that representm eta-identifierss, emantict erms,o r both. All meta-identifierst hat
contain more than one word are written as a unit with hyphensjo ining the parts. Semantict erms ending
in “type” and “variable” are also written as one hyphenatedu nit. Semantict erms representingc ompound
ideasa re likewise written as hyphenatedu nits, e.g., digit-value, activation-point,a ssignment-compatible,
and identifying-value.
NOTES are included in this InternationalS tandardo nly for purposeso f clarification, and aid in the use of
the standard.N OTES are informative only and are not a part of the InternationalS tandard.
Examplesi n this InternationalS tandarda re equivalentt o NOTES.
5 Compliance
There are two levels of compliance,l evel 0 and level 1. Level 0 does not include conformant-array-
parameters.L evel 1 doesi nclude conformant-array-parameters.
5.1 Processors
A processorc omplying with the requirementso f this InternationalS tandards hall
a) if it compliesa t level 0, accepta ll the featureso f the languages pecifiedi n clause6 , exceptf or 6.6.3.6
e), 6.6.3.7, and 6.6.3.8, with the meaningsd efinedi n clause6 ;
b) if it compliesa t level 1, accepta ll the featureso f the languages pecifiedi n clause6 with the meanings
definedi n clause6 ;
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ISO/IEC 7185:1990(E)
c) not require the inclusion of substituteo r additional languagee lementsi n a program in order to
accomplisha featureo f the languageth at is specifiedi n clause6 ;
d) be accompaniedb y a documentt hat providesa definition of all implementation-deEnefde atures;
e) be able to determinew hether or not the program violates any requirementso f this International
Standard,w here such a violation is not designateda n error, report the result of this determination
to the user of the processorb efore the executiono f the program-block, if any, and shall prevent
executiono f the program-block,i f any;
f) treat eachv iolation that is designateda n error in at least one of the following ways
1) there shall be a statementi n an accompanyingd ocumentt hat the error is not reported,a nd a
note referencinge ach such statements hall appeari n a separates ectiono f the accompanying
document;
2) the processors hall report the error or the possibility of the error during preparationo f the
program for execution and in the event of such a report shall be able to continue further
processinga nd shall be able to refusee xecutiono f the program-block;
3) the processors hall report the error during executiono f the program;
and if an error is reportedd uring executiono f the program,t he processors hall terminatee xecution;
if an error occursw ithin a statement,t he executiono f that statements hall not be completed;
NOTE - 1 This means that processing will continue up to or beyond execution of the program at the option
of the user.
g) be accompaniedb y a documentt hat separatelyd escribesa ny featuresa cceptedb y the processort hat
are prohibitedo r not specifiedi n clause6 : such extensionss hall be describeda s being ‘extensions
to Pascala s specifiedb y ISO/IEC 7 185’;
h) be able to process,i n a manners imilar to that specifiedf or errors, any useo f any such extension:
i) be able to process,i n a manners imilar to that specifiedf or errors, any use of an implementation-
dependenfte ature.
NOTE - 2 The phrase ‘be able to’ is used in 5.1 to permit the implementation of a switch with which the user may
control the reporting.
A processorth at purportst o comply,w holly or partially, with the requirementso f this InternationalS tandard
shall do so only in the following terms. A compliances tatements hall be producedb y the processora s a
consequenceo f using the processoro r shall be includedi n accompanyingd ocumentation.I f the processor
complies in all respectsw ith the requirementso f this International Standard,t he compliances tatement
shall be
<This processor> compliesw ith the requirementso f level <number> of ISO/IEC 7 185.
If the processorc omplies with someb ut not all of the requirementso f this InternationalS tandardt hen it
shall not use the aboves tatementb, ut shall insteadu set he following compliances tatement
<Thisprocessor>c ompliesw ith ther equirementso f level <number> of ISO/IEC 7 185,w ith the following
exceptions: <followed by a referencet o, or a completel ist of, the requirementso f the International
Standardw ith which the processord oesn ot comply>.
In both cases the text <This processory shall be replacedb y an unambiguousn ame identifying the
processor,a nd the text <number> shall be replacedb y the appropriatel evel number.
NOTE - 3 Processors that do not comply fully with the requirements of the International Standard are not required to
give full details of their failures to comply in the compliance statement; a brief reference to accompanying documentation
that contains a complete list in sufficient detail to identify the defects is sufficient.
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ISO/IEC 7185:1990(E)
5.2 Programs
A programc onforming with the requirementso f this InternationalS tandards hall
a) if it conforms at level 0, use only those featureso f the languages pecified in clause6 , except for
6.6.3.6 e), 6.6.3.7, and 6.6.3.8;
b) if it conformsa t level 1, use only thosef eatureso f the languages pecifiedi n clause6 ; and
c) not rely on any particular interpretationo f implementation-dependenfeta tures.
NOTES
1 A program that complies with the requirements of this International Standard may rely on particular implementation-
defined values or features.
2 The requirements for conforming programs and compliant processors do not require that the results produced by a
conforming program are always the same when processed by a compliant processor. They may be the same, or they
may differ, depending on the program. A simple program to illustrate this is
program x(output); begin writeln(maxint) end.
6 Requirements
6.1 Lexical tokens
NOTE - The syntax given in this subclause describes the formation of lexical tokens from characters and the separation
of these tokens and therefore does not adhere to the same rules as the syntax in the rest of this International Standard.
6.1.1 General
The lexical tokensu sedt o constructP ascalp rogramsa rec lassifiedi nto special-symbolsi,d entifiers,d irectives,
unsigned-numbersla, bels,a ndc haracter-stringsT. he representationo f any letter (upperc aseo r lower case,
differenceso f font, etc.) occurringa nywhereo utsideo f a character-string(s ee6 .1.7) shall be insignificant
in that occurrencet o the meaningo f the program.
letter = ‘a’ 1‘ b’ I ‘c’ 1 ‘d’ 1 ‘e’ I ‘f’ I ‘g’ I ‘h’ I ‘i’ I ‘j’
1 ‘k’ I ‘I’ I ‘m’ I ‘n’ I ‘0’ I ‘p’ I ‘q’ I ‘r’ I ‘s’ I ‘t’
1 ‘u’ 1 ‘v’ 1 ‘w’ 1 ‘x’ 1 ‘y’ 1 ‘z’ .
digit = ‘0’ I ‘1’ I ‘2’ I ‘3’ I ‘4’ I ‘5’ I ‘6’ I ‘7’ I ‘8’ I ‘9’ .
6.1.2 Special-symbols
The special-symbolsa re tokensh aving specialm eaningsa nd are usedt o delimit the syntacticu nits of the
language.
special-symbol = 1;’ ,I:;‘, 1‘ *’ 1‘ /’ 1‘ =’ 1‘ c’ 1‘ >’ 1‘ [’ 1‘ I’
r:* 1d ;, 1‘ TV1 S (, 1‘ ),
I
1 ‘<z’ i ‘<=’ 1‘ >=’ 1‘ :=’ 1‘ ..’ 1w ord-symbol .
word-symbol = ‘and’ j ‘array’ I ‘begin’ I ‘case’ I ‘const’ I ‘div’
I ‘do’ j ‘downto’ I ‘else’ I ‘end’ I ‘file’ I ‘for’
I ‘function’ I ‘goto’ j ‘if’ I ‘in’ j ‘label’ I ‘mod’
I ‘nil’ I ‘not’ I ‘of’ I ‘or’ I ‘packed’ I ‘procedure’
I ‘program’ j ‘record’ I ‘repeat’ I ‘set’ I ‘then’
I ‘to’ I ‘type’ I ‘until’ I ‘var’ I ‘while’ I ‘with’ .
5
