ISO/IEC INTERNATIONAL STANDARD 1539-1 Fifth edition 2023-11 Programming languages Fortran Part 1: Base language Langages de programmation - Fortran - Partie 1: Langage de base Reference number IEC ISO/IEC 1539-1:2023(E) OSI @IS0/IEC2023 IS0/IEC 1539-1:2023(E) COPYRIGHT PROTECTED DOCUMENT IS0/IEC2023 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either Iso at the address below or ISO's member body in the country of the requester. ISO copyright office CP 401 · Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +4122 749 0111 Email: [email protected] Website: www.iso.org Published in Switzerland ii @IS0/IEC 2023-All rights reserved ISO/IEC 1539-1:2023 (E) Contents Foreword xii Introduction xii 1 Scope 2 Normative references N Terms and definitions 3 4 Notation, conformance, and compatibility 30 Notation, symbols and abbreviated terms 30 4.1.1 Syntax rules 30 4.1.2 Constraints 31 4.1.3 Assumed syntax rules 31 4.1.4 Syntax conventions and characteristics 31 4.1.5 Text conventions 32 4.2 32 4.3 Compatibility 33 4.3.1 Previous Fortran standards 33 4.3.2 New intrinsic procedures 33 4.3.3 Fortran 2018 compatibility 33 4.3.4 Fortran 2008 compatibility 34 4.3.5 Fortran 2003 compatibility 35 4.3.6 Fortran 95 compatibility 36 4.3.7 Fortran 90 compatibility 36 4.3.8 FORTRAN 77 compatibility 37 4.4 Deleted and obsolescent featu 37 4.4.1 General 37 4.4.2 Nature of deleted feature 37 4.4.3 Nature of obsolescent features 38 5 Fortran concepts 39 5.1 High level syntax 39 5.2 Program unit concept: 42 5.2.1 Program units and scoping units 42 5.2.2 Program 42 5.2.3 Procedure 42 5.2.4 Module 43 5.2.5 Submodule 43 5.3 Execution concepts 43 5.3.1 Statement classification 43 5.3.2 Statement order 43 5.3.3 The END statement 44 5.3.4 Program execution 44 5.3.5 Execution sequence 45 @ IS0/IEC 2023 - All rights reserved ii ISO/IEC 1539-1:2023 (E) 5.3.6 Imageexecution 45 5.3.7 Termination of execution 46 5.4 Data concepts 46 5.4.1 Type 46 5.4.2 Data value 47 5.4.3 Data entity 47 5.4.4 Definition of objects and pointers 48 5.4.5 Reference 49 5.4.6 Array 5.4.7 Coarray 49 5.4.8 Established coarrays 50 5.4.9 Pointer 50 5.4.10 Allocatable variables 50 5.4.11 Storage 51 5.5 Fundamental concepts 51 5.5.1 Names and designators 51 5.5.2 Statement keyword 51 5.5.3 Other keywords 51 5.5.4 Association 51 5.5.5 Intrinsic 51 5.5.6 Operator 52 5.5.7 Companion processors 52 6 Lexical tokens and source form 53 6.1 Processor character set 53 6.1.1 Character 53 6.1.2 Letters 53 6.1.3 Digits 53 6.1.4 Underscore 53 6.1.5 Special characters 53 6.1.6 Other characters 54 6.2 Low-level syntax 54 6.2.1 Tokens 54 6.2.2 Names 54 6.2.3 Constants 55 6.2.4 Operators 55 6.2.5 Statementlabels 56 6.2.6 Delimiters 56 6.3 Source form 57 6.3.1 Program units , statements, and lines 57 6.3.2 Free source form 57 6.3.3 Fixed source form 58 6.4 Including source text 59 Types 61 7.1 Characteristics of type 61 7.1.1 The concept of type 61 7.1.2 Type classification 61 7.1.3 Set of values 61 7.1.4 Constants 61 7.1.5 Operations 61 7.2 Type parameters 62 7.3 Types, 63 7.3.1 Relationship of types and values to objects 63 7.3.2 Type specifiers 63 7.3.3 Type compatibility 65 iv @ ISO/IEC 2023 - All rights reserved ISO/IEC 1539-1:2023 (E) 7.4 Intrinsic 66 7.4.1 Classification and specification 66 7.4.2 Intrinsic operations on intrinsic types 66 7.4.3 Numeric intrinsic types 66 7.4.4 Charactertype 70 7.4.5 Logical type 73 7.5 Derived types 73 7.5.1 Derived type concepts 73 7.5.2 Derived-type definition 74 7.5.3 Derived-type parameters 77 7.5.4 Components 79 7.5.5 Type-bound procedure: 85 7.5.6 Final subroutines 88 7.5.7 Typeextension 90 7.5.8 Derived-type values 92 7.5.9 Derived-type specifier 92