Rationale for International Standard - Programming Language - C UNIX is a trademark of X/Open Co., Ltd.. DEC and PDP-11 are trademarks of Digital Equipment Corporation. POSIX is a trademark of IEEE. CONTENTS 1. SCOPE...........................................................................................................................................................1 1.2 ORGANIZATION OF THE DOCUMENT............................................................................................................5 2. NORMATIVE REFERENCES.....................................................................................................................7 3. DEFINITIONS AND CONVENTIONS ........................................................................................................9 4. COMPLIANCE ...........................................................................................................................................11 5. ENVIRONMENT......................................................................................................................................13 5.1 CONCEPTUAL MODELS..............................................................................................................................13 5.1.1 Translation environment ................................................................................................................13 5.1.1.1 Program structure......................................................................................................................................13 5.1.1.2 Translation phases .......................................................................................................................................13 5.1.1.3 Diagnostics .................................................................................................................................................14 5.1.2 Execution environments....................................................................................................................14 5.1.2.1 Freestanding environment.............................................................................................................................14 5.1.2.2 Hosted environment.....................................................................................................................................15 5.1.2.3 Program execution .......................................................................................................................................15 5.2 ENVIRONMENTAL CONSIDERATIONS ..........................................................................................................17 5.2.1 Character sets ...................................................................................................................................17 5.2.1.1 Trigraph sequences ......................................................................................................................................17 5.2.1.2 Multibyte characters.....................................................................................................................................18 5.2.2 Character display semantics ..............................................................................................................19 5.2.3 Signals and interrupts .......................................................................................................................20 5.2.4 Environmental limits.........................................................................................................................20 5.2.4.1 Translation limits.........................................................................................................................................20 5.2.4.2 Numerical limits..........................................................................................................................................20 5.2.4.2.1 Sizes of integer types <limits.h> ............................................................................................................21 5.2.4.2.2 Characteristics of floating types <float.h> ...............................................................................................21 6. LANGUAGE.................................................................................................................................................23 6.1 LEXICAL ELEMENTS .................................................................................................................................23 6.1.1 Keywords..........................................................................................................................................23 6.1.2 Identifiers .........................................................................................................................................23 6.1.2.1 Scopes of identifiers.....................................................................................................................................25 6.1.2.2 Linkages of identifiers..................................................................................................................................26 6.1.2.3 Name spaces of identifiers ............................................................................................................................27 6.1.2.4 Storage durations of objects ..........................................................................................................................28 6.1.2.5 Types .........................................................................................................................................................28 6.1.2.6 Compatible type and composite type..............................................................................................................30 6.1.2.7 Predefined identifiers...................................................................................................................................31 6.1.2.8 Representations of types ...............................................................................................................................31 6.1.2.8.1 General...............................................................................................................................................31 6.1.8.2 Integer types...........................................................................................................................................31 6.1.3 Constants..........................................................................................................................................31 6.1.3.1 Floating constants ........................................................................................................................................31 6.1.3.2 Integer constants..........................................................................................................................................31 6.1.3.3 Enumeration constants .................................................................................................................................32 6.1.3.4 Character constants......................................................................................................................................32 6.1.4 String literals ....................................................................................................................................33 6.1.5 Operators..........................................................................................................................................35 6.1.6 Punctuators ......................................................................................................................................35 6.1.7 Header names...................................................................................................................................35 6.1.8 Preprocessing numbers .....................................................................................................................36 6.1.9 Comments ........................................................................................................................................36 6.2 CONVERSIONS ..........................................................................................................................................37 i CONTENTS 6.2.1 Arithmetic operands..........................................................................................................................37 6.2.1.1 Characters and integers ................................................................................................................................37 6.2.1.2 Signed and unsigned integers........................................................................................................................38 6.2.1.3 Real floating and integer...............................................................................................................................38 6.2.1.4 Real floating types .......................................................................................................................................38 6.2.1.5 Complex types.............................................................................................................................................39 6.2.1.6 Real and complex ........................................................................................................................................39 6.2.1.7 Usual arithmetic conversions ........................................................................................................................39