CAN CSA-ISO IEC 10206-1994 Information Technology - Programming Languages - Extended Pascal.pdf

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1、INTER NATIONAL STANDARD ISOAEC 10206 First edition 1991 -04-1 5 (Reaffirmed 2004) Information technology - Programming languages - Extended Pascal Langages de programmation - Pascai Btendu National Standard of Canada CAN/CSA-ISO/IEC-l0206=94 International Standard ISO/IEC 10206:1991 has been adopted

2、, without modification, as CAN/CSA-ISO/IEC- 10206-94, which has been approved as a National Standard of Canada by the Standards Council of Canada. November 1994 Reference number ISO/IEC 10206 : 1991 (E) - - -_ - ISO/IEC 10206 : 1991 (E) Contents Introduction . Page v1 Scope Normative reference Defin

3、itions 3.1 Dynamic-violation . 3.2 Error 3.3 Extension 3.4 Implementation-defined *. . 1 1 1 . 2 2 . . 2 . 2 . 2 2 3.5 Implementation-dependent 3.6 Processor . Definitional conventions . Compliance 5.1 Processors . 5.2 Programs . 4 5 2 6 Requirements . 6.1 Lexical tokens . 5 5 5 6 6 6 7 7 7 8 Genera

4、l. Special-symbols Id en t i fiers . Rem0 te-directives Interface-directives . 6.1.1 6.1.2 6.1.3 6.1.4 6.1.5 6.1.6 6.1.7 6.1.8 . . . . . Implementation-directives . Numbers . Labels 0 ISO/IEC 1991 All rights reserved. No parr of this publication may be reproduced or utilized in any form or by any me

5、ans, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. Printed in Switzerland ISO/IEC Copyright Office K Case postale 56 K CH-1211 Geneve 20 K Switzerland II ISO/IEC 10206 : 1991 (E) 6.1.9 Character.strings . 6.1.10 Token separators . 6

6、.1.11 Lexical alternatives Blocks. scopes. activations. and states . 6.2.1 Blocks 6.2.2 Scopes 6.2.3 Activations 6.2.4 States 6.3 Constants . 6.2 . 6.3.1 General 6.3.2 Example of a constant-definition-part . 6.4 Types and schemata . 6.4.1 Type-deficitions . 6.4.2 Simple-types 6.4.3 Structured-types

7、. 6.4.4 Pointer-types 6.4.5 Compatible types 6.4.6 Assignment-compatibility . 6.4.7 Schema-definitions . 6.4.8 Discriminated-schemata . 6.4.9 Type-inquiry 6.4.10 Example of a type-definition-part . 6.5 Declarations and denotations of variables 6.5.1 Variable-declarations . 6.5.2 Entire-variables 6.5

8、.3 Component-variabIes . 6.5.4 Identified-variables . 6.5.5 Buffer-variables . 6.5.6 Substring-variables . 6.6 Initial states . 6.7 Procedure and function declarations 6.7.1 Procedure-declarations . 6.7.2 Function-declarations 6.7.3 Parameters 6.7.4 Required procedures and functions . 6.7.5 Required

9、 procedures 6.7.6 Required functions . 6.8 Expressions 6.8.1 General . 6.8.2 Constant-expressions . 8 9 9 10 10 10 13 15 16 16 17 17 17 19 24 32 33 33 34 35 36 36 38 38 39 39 41 41 42 42 43 43 45 48 56 56 63 69 69 71 . 111 ISO/IEC 10206 : 1991 (E) 6.8.3 Operators . 6.8.4 Schema-discriminants 6.8.5 F

10、unction-designators . 6.8.6 Function-accesses 6.8.7 Structured-value-constructors 6.8.8 Constant-accesses 6.9 Statements . 6.9.1. General . 6.9.2 Simple-statements 6.9.3 Structured-statements 6.9.4 Threats . 6.10 Input and output . 6.10.1 The procedure read . 6.10.2 The procedure readln . 6.10.3 The

11、 procedure write 6.10.4 The procedure writeln 6.10.5 The procedure page 6.11 Modules 6.11.1 Module-declarations 6.11.2 Export-part . 6.11.3 Import-specifications . 6.11.4 Required interfaces . 6.11.5 Example of a module . 6.11.6 Examples of program-components that are module- declarations . Example

12、of exporting a range of enurnerated-type values . 6.12 Main-program-declarations 6.11.7 6.13 Programs . Annexes Annex A Annex B Annex C Annex D Annex E Annex F Annex G Index . Collected syntax Incompatibilities with Pascal standards Required identifiers . Errors and d ynamic-violations Implementatio

13、n-defined features Implementation-dependent features . Bibliography . . 71 75 76 76 78 80 82 82 82 84 90 91 91 92 93 96 97 97 97 99 100 102 102 104 111 112 114 116 176 177 178 186 189 191 192 ISO/IEC 10206 : 1991 (E) Foreword IS0 (the International Organization for Standardization) and IEC (the Inte

14、rnational Electrotechnical Commission) form the specialized system for worldwide standardiz- ation. NationaI 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

15、 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 estabhhed

16、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 Vo of the national bodies casting a vote. International Standard

17、ISO/IEC 10206 was prepared by joint Technical Committee ISO/IEC JTC 1, Information technology. Annexes A to G are for information only. V ISO/IEC 10206 : 1991 (E) Introduction This International Standard provides an unambiguous and machine independent definition of the programming language Extended

18、Pascal. Its purpose is to facilitate portability of Extended Pascal programs for use on a wide variety of data processing systems. Language history The computer programming language Pascal was designed by Professor Niklaus Wirth to satisfy two principal aims a) to make available a language suitable

19、for teaching programming as a systematic discipline based on b) to define a language whose implementations could be reliable and efficient on then-available certain fundamental concepts clearly and naturally reflected by the language; computers. However, it has become apparent that Pascal has attrib

20、utes that go far beyond those original goals. It is now being increasingly used commercially in the writing of system and application software. With this increased use, there has been an increased demand for and availability of extensions to IS0 7 185: 1983, Programming languages - PASCAL. Programs

21、using such extensions attain the benefits of the extended features at the cost of portability with standard Pascal and with other processors supporting different sets of extensions. In the absence of a standard for an extended language, these processors have become increasingly incompatible. This In

22、ternational Standard is primarily a consequence of the growing commercial interest in Pascal and the need to promote the portability of Pascal programs between data processing systems. Project history In 1977, a working group was formed within the British Standards Institution (BSI) to produce a sta

23、ndard for the programming language Pascal. This group produced several working drafts, the first draft for public comment being widely published early in 1979. In 1978, BSIs proposal that Pascal be added to ISOs programme of work was accepted, and the IS0 Pascal Working Group (then designated ISO/TC

24、97/SC5/WG4) was formed in 1979. The Pascal standard was to be published by BSI on behalf of ISO, and this British Standard referenced by the International Standard. In the USA, in the fall of 1978, application was made to the IEEE Standards Board by the IEEE Computer Society to authorize project 770

25、 (pascal). After approval, the first meeting was heId in January 1979. In December 1978, X3J9 convened as a result of a SPARC (Standards Planning and Requirements Committee) resolution to form a US TAG (Technical Advisory Group) for the IS0 Pascal standardization effort initiated by the UK. These ef

26、forts were performed under X3 project 317. In agreement with IEEE representatives, in February 1979, an X3 resolution combined the X3J9 and P770 committees into a single committee called the Joint X3J9/IEEE W70 Pascal Standards Committee. (Throughout, the term PC refers to this committee.) The first

27、 meeting as JPC was heId in April 1979. The resolution to form PC clarified the dual function of the single joint committee to produce a dpANS and a proposed IEEE Pascal standard, identical in content. ANSI/IEEE770X3.97- 1983, American National Standard Pascal Computer Programming Language, was appr

28、oved by the IEEE Standards Board on September 17,1981, and by the American National Standards Institute on December 16, 1982. British Standard BS6192, Specification for Computer programming language Pascal, was published in 1982, and International Standard 7185 (incorporating BS6192 by reference) wa

29、s approved by IS0 on December 1,1983. Differences between the ANSI and IS0 standards are detailed in the Foreword of ANSI/IEEE77OX3.97-T983. (BS6192/IS07185 was revised and corrected during 1988/89; it is expected that ANSI/IEEE770X3.97-1983 will be replaced by the revised IS0 7185.) vi ISO/IEC 1020

30、6 : 1991 (E) Following the decision that the first publication of a standard for the programming language Pascal would not contain extensions to the language, Jfc prepared a project proposal to SPARC for an Extended Pascal Standard. When approved by X3 in November 1980, this proposal formed the char

31、ter for Projzct 345. JPC immediately formed the Extension Task Group to receive all proposals for extensions to the PascaI language, developed the content of proposals so that they were in a form suitable for review by JPC, fairly and equitably reviewed all proposals in light of published JPC policy

32、, and provided a liaison with the public in all matters concerning proposed extensions to the Pascal language. X3 issued a press release on behalf of JPC in January 1980 to solicit extension proposals or suggestions from the generaI public. At this time, JFC had already prepared a list of priority e

33、xtensions; public comment served to validate and supplement the priority list. Criteria for evaluating extensions were established and included machine independence, upward compatibility, conceptual integrity, rigorous definition, and existing practice as prime objectives. Extension proposals submit

34、ted by the public and by the JPC membership were developed and refined. PC procedures guaranteed that proposals would be considered over at least two meetings, affording adequate time for review of the technical merits of each proposal. By June of 1983, twelve extensions had been designated by JPC a

35、s candidate extensions and were published as a Candidate Extension Library. Ongoing work was described in Work in Progress, published with the Candidate Extension Library. This effort served as an interim milestone and an opportunity for the public to review the effort to date. In 1984, BSI also sta

36、rted work on extensions to Pascal, with an initial aim of providing extensions in a few areas only. In 1985, the IS0 Pascal Working Group (then designated ISO/TC97/SC22/WG2, now ISO/IEC JTCl/SC22/WG2) was reconvened after a long break to consider proposals from both ANSI and BSI in an international

37、forum. Thereafter WG2 met at regular intervals to reconcile fie national standardization activities in ANSI and BSI and to consider issues raised by the other experts participating in WG2. The Work in Progress, along with other proposals subsequently received, continued its development until June 19

38、86. The process of reconciling individual candidate extensions among themselves was begun in September 1984 and continued until June 1986. During this phase, conflicts between changes were resolved and each change was reconsidered. Working drafts of the full standard were circulated within PC and WG

39、2 to incorporate changes from each meeting. The candidate extensions were then integrated into a draft standard that was issued for public review. The Public Comment Task Group (PCTG) was formed to respond to the public comments and recommend changes to the draft. To promote a unified response on ea

40、ch comment issue, PCTG included members from both WG2 and JPC. All responses and recommended changes required final approval by JPC and WG2. PCTG recommended several substantive changes that were subsequently approved as changes to the draft. These changes were incorporated and a new draft was produ

41、ced for a second public review. Project charter The goal of JPCs Project 345 was to define an implementable, internationally acceptable Extended Pascal Standard. This International Standard was to encompass those extensions found to be a) compatible with ANSILlEEE770X3.97- 1983, American National St

42、andard Programming Language Pascal, and b) beneficial with respect to cost. JPCs approved program of work included: a) solicitation of proposals for extended language features; vii ISWIEC 10206 : 1991 (E) b) the critical review of such proposals; c) synthesis of those features found to be acceptable

43、 individually and which are mutually consistent into a working draft proposed standard; d) interface with all interested standards bodies, both domestic and international; e) submission of the working draft to ISO/TC97/SC22/wG2; f) synthesis and submission of a draft proposed ANS consistent with any

44、 international standard g) review and correction of the dpANS in light of any comment received during Public Comment and/or developed; Trial Use periods. Technical deveIopment Extended Pascal incorporates the features from ANSIEEE770X3.97- 1983 and the following new features: a) Modularity and Separ

45、ate compilation. Modularity provides for separately-compilable program -Each module exports one or more interfaces containing entities (values, types, schemata, variables, procedures, and functions) from that module, thereby controlling visibility into the module. components, while maintaining type

46、security. -A variable may be protected on export, so that an importer may use it but not alter its value. -The form of a module cIearly separates its interfaces from its internal details. A type may be restricted, so that its structure is not visible, -Any block may import one or more interfaces. Ea

47、ch interface may be used in whole or in part. Entities may be accessed with or without interface-name qualification. Entities may be renamed on export or import. -Initialization and finalization actions may be specified for each module. -Modules provide a framework for implementation of libraries an

48、d non-Pascal program b) Schemata. A schema determines a collection of similar types. Types may be selected statically or components. dynamically from schemata. -Statically selected types are used as my other types are used. -Dynamically selected types subsume dl the functionality of, and provide fun

49、ctional capability beyond, conformant arrays. -The dlocation procedure new may dynamically select the type (and thus the size) of the allocated variable. -A schematic formal-parameter adjusts to the bounds of its actual-parameters. -The declaration of a local variable may dynamically select the type (and thus the size) of the variable. -The with-statement is extended to work with schemata. Fomal schema discriminants can be used as variant selectors. . Vlll ISO/IEC 10206 : 1991 (E) c) String Capabilities. The comprehensive string facilities unify fixed-length strings and character