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1、ANSI INCITS 74-1987 (R1998) (formerly ANSI X3.74-1987 (R1998) for Information Systems - Programming Language - PL/I General-purpose Subset Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=OConnor, Maurice Not for Resale,
2、04/29/2007 05:44:38 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI X3.74-1987 Revision of ANSI X3.74-1981 American National Standard for Information Systems - Programming Language - PL/I General-Purpose Subset Secretariat Computer and Business Equipment Manufacturers
3、Association Approved September 4,1987 American National Standards Institute, Inc Abstract This American National Standard defines the PL/I general-purpose subset programming language. The language isequally well suited for scientific, commercial, and systems programming applications. It provides a h
4、igh degree of machine independence, thereby facilitating program exchange among a variety of computing systems. The language can be efficiently implemented on computer systems of all sizes, including minicomputer and microprocessor-based systems, This standard specifies both the form and interpretat
5、ion of computer programs written in PL/I. It defines the language by specifying a conceptual PL/I machine that translates and interprets putative PL/I programs. The relationship between that conceptual machine and actual implementations of PL/I is also specified. This document serves as an authorita
6、tive reference rather than as a tutorial exposition. Keywords: PL/I, computer programming language, computer programming language definition, formal languages. Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=OConnor, Mau
7、rice Not for Resale, 04/29/2007 05:44:38 MDTNo reproduction or networking permitted without license from IHS -,-,- American National Standard Approval of an American National Standard requires review by ANSI that the requirements for due process, consensus, and other criteria for approval have been
8、met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Con
9、sensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufa
10、cturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the
11、right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for interpretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. CAUTION NOTICE: This American
12、 National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute require that action be taken periodically to reaffirm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards
13、 by calling or writing the American National Standards Institute. Published by American National Standards Institute 11 West 42nd Street, New York, New York 10036 Copyright 1987 by Information Technology Industry Council (ITI) All rights reserved. No part of this publication may be reproduced in any
14、 form, in an electronic retrieval system or otherwise, without prior written permission of ITI, 1250 Eye Street NW, Washington, DC 20005. Printed in the United States of America Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001,
15、 User=OConnor, Maurice Not for Resale, 04/29/2007 05:44:38 MDTNo reproduction or networking permitted without license from IHS -,-,- Foreword (This Foreword is not part of AMERICAN NATIONAL STANDARD X3.74-1987.) In October 1963, a committee was formed by the SHARE FORTRAN Project and the Internation
16、al Business Machines Corporation to extend FORTRAN, then the primary high-level language used by scientific programmers. The extended language was to be suitable for commercial and systems programs as well and was to take into account the architecture of modern computers. The committee soon determin
17、ed that the language would have to differ from FORTRAN, and their report, presented in April 1964, was entitled “Specifications for the New Programming Language”. The New Programming Language was widely discussed. Revised descriptions were issued, and in 1965 it was renamed PL/I (for programming lan
18、guage one). Versions were implemented on the computers of at least two manufacturers by late 1966. By April 1966, Technical Committee 10 (TC 10) had been set up by the European Computer Manufacturers Association (ECMA) and an ad hoc group by American National Standards Committee X3 to investigate th
19、e development of PL/I standards. TC 10 embarked immediately on standardization but the Standards Institute group first considered whether,PL/I was a suitable candidate. Early in 1969 Technical Committee X3Jl was formed by American National Standards Committee X3 to carry out the work in conjunction
20、with TC 10. The two technical committees, X3Jl and TC 10, formed the joint PL/I standardization project. Building on the work begun by TC 10, nearly 3500 proposals for language or textual change were processed in developing a joint draft standard for PL/I. The joint working document underwent thirte
21、en complete revisions. During this time, the definition evolved from an imprecise English description to a precise specification in a semiformal metalanguage using a stylized English. The Joint Project enjoyed excellent liason with potential users and with other standards organizations such as Inter
22、national Organization for Standardization Technical Committee 97, Subcommittee 5 (ISO/TC 97/SC 5) and PL/I working groups in Austria, France, Germany, the Netherlands, Japan, and the United Kingdom. That standard development effort led, in August 1976, to the adoption of ANSI X3.53-1976, American Na
23、tional Standard Programming Language PL/I. While there were, and continue to be, several implementations of that language, the interests of parts of the user community turned toward the development of a smaller language - a proper subset of PL/I as described in ANSI X3.53-1976 - that would be easier
24、 to implement and use on a wide variety of machines and that would provide a higher degree of compatibility with various dialects of PL/I that had arisen in practice. A standard development process ensued, with broad participation from within the U.S. and continued close liason with users and other
25、standards organizations. That effort led, in July 1981, to the adoption of American National Standard PL/I General Purpose Subset, ANSI X3.74- 198 1. That document described a small subset of ANSI X3.53-1976, and its language was defined as a series of constraints and restrictions on the definitions
26、 in ANSI X3.53-1976. Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=OConnor, Maurice Not for Resale, 04/29/2007 05:44:38 MDTNo reproduction or networking permitted without license from IHS -,-,- Technical Committee X3Jl
27、 then turned its efforts, in mid 1981, to reviews of ANSI X3.53-1976 and ANSI X3.74-198 1. At that early date, two trends in the marketplace already seemed clear: 1. Contrary to expectations of the Technical Committee and other participants only a few years earlier, the language described by the Sub
28、set appeared to be too restrictive for many practical uses. By early 1982, this had already begun to be reflected in common practice, as most subset implementations adopted additional features from ANSI X3.53-1976 as extensions. 2. While the implementations of ANSI X3.53-1976 have been heavily used,
29、 there are not many of them and difficult incompatibilities remained between them and older dialects of PL/I. It proved impossible to reach an adequate consensus on how to resolve these dialects at a complete language level. At the same time, there was little pressure for major extensions or modific
30、ations to the full PL/I as represented by ANSI X3.53-1976. The precision of the definition method had resulted in very few ambiguities or requests for clarification and, while additions were proposed, most reflected experience in existing implementations and none required incompatible change to the
31、language as approved in 1976. X3Jl considered over 1200 proposals between 198 1 and 1986, some oriented specifically toward extending and modifying the Subset definition, and others oriented toward PL/I language issues more generally. After a review of this body of work and the practice and directio
32、ns of the PL/I community, the technical committee concluded that it should strengthen the language represented by this document to make it truly general-purpose, to reflect common practice among implementations supporting the 198 1 version of the standard, and to provide a common basis for program i
33、nterchange among the variety of PL/I dialects. Since this standard contains language features that, while already present in PL/I implementations, were not present in ANSI X3.53-1976, it has been necessary, technically, to make this definition self-contained, rather than referring to that other stan
34、dard. Suggestions for improvement of this standard will be welcome. They should be sent to the Computer and Business Equipment Manufacturer s Association, 3 11 First Street, N.W., Suite 500, Washington, DC, 20001. This standard was processed and approved for submittal to ANSI by Accredited Standards
35、 Committee on Information Processing Systems X3. Committee approval of the standard does not necessarily imply that all committee members voted for its approval. At the time it approved this standard, the X3 Committee had the following members: Richard Gibson, Chair Donald C. Loughry, Vice Chair Cat
36、herine A. Kachurik, Administrative Secretary PRODUCERS Organization Represented Name of Representative Ah4P Incorporated AT the datasets may change during interpretation. However, there are no outputs defined since the datasets are treated for the purposes of this definition as being a part of the s
37、torage of the machine, i.e. as being “on-line” when needed. 1. Scope and Overviews 5 Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=OConnor, Maurice Not for Resale, 04/29/2007 05:44:38 MDTNo reproduction or networking p
38、ermitted without license from IHS -,-,- AMERICAN NATIONAL STANDARD X3.74-1987 1.4.3 Summary of Chapter Structure l.TOP-LEVEL OF MACHINE-STATE AND OPERATIONS 2.CONCRETE SYNTAX j.ABSTRACT SYNTAX +.TRANSLATOR 5.INTERPRETATION-STATE + TOP-LEVEL OF INTERPRETER .FLOW OF CONTROL Concerned with the 7.STORAG
39、E AND ASSIGNMENT 8.INPUT/OUTPUT It- three parts of the interpretation-state g.EXPRESSIONS Common Subroutines for Chapters 5-8 Appendix A: FEATURES NEW TO THIS REVISION ADOPTED FROM X3.53-1976 Appendix B: FEATURES NEW TO THIS REVISION Appendix C: CLARIFICATIONS AND RESTRICTIONS FROM x3.74-1981 Append
40、ix D: FEATURES OF X3.53-1976 NOT ADOPTED IN THIS STANDARD Appendix E: INCOMPATIBLE CHANGES FROM X3.74-1981 Appendix F: RATIONALE FOR MAJOR DESIGN DECISIONS The operations of Chapter 1 serve to drive the Translator and Interpreter. The operations of the Translator are all contained in Chapter 4, and
41、use the syntaxes of Chapters 2 and 3. The operations of the Interpreter comprise all the operations in Chapters 5-9. After the initialization in Chapter 5, the relevant operations will be in Chapters 6,7, or 8 depending on the type of statement being interpreted. All of these chapters invoke operati
42、ons in Chapter 9 where necessary. All readers are recommended to acquire a good understanding of Chapter 1 in its entirety. Thereafter, it is possible to read the definition as a systematic whole, or to use the document to locate answers to specific questions by combining an appreciation of the over
43、all structure of the definition with judicious use of the index. To illustrate this latter usage, we consider each chapter in turn together with a sample question answerable from it. Chapter 2 contains the definition of the Concrete Syntax. The Concrete Syntax consists of rules describing valid form
44、s of PL/I constructs in concrete tree form. The syntax is permissive in the sense that some of the constructs permitted as being syntactically correct may later be found to be meaningless. 6 Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employee
45、s/1111111001, User=OConnor, Maurice Not for Resale, 04/29/2007 05:44:38 MDTNo reproduction or networking permitted without license from IHS -,-,- AMERICAN NATIONAL STANDARD X3.74-1987 QUESTION Is the following statement correct? GET LIST (A(I,J) DO I = 1 TO M,N); ANSWER The first possibility is that
46、 there may be an error according to the Concrete Syntax. The index entries for “get-statement” lead to the High-level Syntax, and study of rules CH115, CH116, CH123, CH124, and CH125 reveals that an extra pair of parentheses is required around the form *input-target-comma Chapter 3 contains the defi
47、nition of the Abstract Syntax. Many parts of the Abstract Syntax description intentionally bear a strong resemblance to the corresponding parts of the Concrete Syntax. Names in the Abstract Syntax have been chosen to resemble those of corresponding parts of the Concrete Syntax in order to make obvio
48、us as far as possible the relationship between the syntaxes. QUESTION May the KEYTO option on a READ statement specify that the key be assigned to a substring of a variable? ANSWER The Concrete Syntax for a *keyto-option+ shows merely that a kreference$ MUST be specified. However, the Abstract Synta
49、x shows the form of a program after the Translator has completed all declarations, and has thus been able to associate each reference with the appropriate declaration and make more subtle distinctions. The rule Al23 for shows “ (scalar AND character)“. The parenthesized constraint “(scalar AND character)” shows that it MUST be a single tar