ISO/IEC 10646:2020

INTERNATIONAL ISO/IEC
STANDARD 10646
Sixth edition
2020-12
Information technology — Universal
coded character set (UCS)
Technologies de l'information — Jeu universel de caractères codés (JUC)
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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CONTENTS
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Conformance .8
4.1 General .8
4.2 Conformance of information interchange .8
4.3 Conformance of devices.8
5 Electronic data attachments .9
6 General structure of the UCS . 10
7 Basic structure and nomenclature . 11
7.1 Structure . 11
7.2 Coding of characters . 12
7.3 Types of code points . 12
7.4 Naming of characters . 13
7.5 Short identifiers for code points (UIDs) . 14
7.6 UCS Sequence Identifiers . 14
7.7 Octet sequence identifiers . 15
8 Revision and updating of the UCS . 15
9 Subsets . 15
9.1 General . 15
9.2 Limited subset . 15
9.3 Selected subset. 15
10 UCS encoding forms . 15
10.1 General . 15
10.2 UTF-8 . 15
10.3 UTF-16 . 16
10.4 UTF-32 . 17
11 UCS encoding schemes . 17
11.1 General . 17
11.2 UTF-8 . 17
11.3 UTF-16BE . 17
11.4 UTF-16LE . 18
11.5 UTF-16 . 18
11.6 UTF-32BE . 18
11.7 UTF-32LE . 18
11.8 UTF-32 . 19
12 Use of control functions with the UCS . 19
13 Declaration of identification of features . 20
13.1 Purpose and context of identification . 20
13.2 Identification of a UCS encoding scheme . 20
13.3 Identification of subsets of graphic characters . 21
© ISO/IEC 2020 – All rights reserved iii

13.4 Identification of control function set . 21
13.5 Identification of the coding system of ISO/IEC 2022 . 21
14 Structure of the code charts and lists . 22
15 Block and collection names . 22
15.1 Block names . 22
15.2 Collection names . 23
16 Mirrored characters in bidirectional context . 23
16.1 Mirrored characters . 23
16.2 Directionality of bidirectional text . 23
17 Special characters . 23
17.1 General . 23
17.2 Space characters . 23
17.3 Currency symbols . 24
17.4 Format characters . 24
17.5 Ideographic description characters . 24
17.6 Variation selectors and variation sequences . 25
18 Presentation forms of characters . 27
19 Compatibility characters . 27
20 Order of characters . 27
21 Combining characters . 28
21.1 Order of combining characters . 28
21.2 Combining class and canonical ordering . 28
21.3 Appearance in code charts . 28
21.4 Alternate coded representations . 28
21.5 Multiple combining characters . 28
21.6 Collections containing combining characters . 29
21.7 Combining Grapheme Joiner . 29
22 Normalization forms. 29
23 Special features of individual scripts and symbol repertoires . 30
23.1 Hangul syllable composition method . 30
23.2 Features of scripts used in India and some other South Asian countries . 30
23.3 Byzantine musical symbols . 31
23.4 Source references for pictographic symbols . 31
24 Source references for CJK ideographs . 32
24.1 List of source references. 32
24.2 Source references file for CJK ideographs . 35
24.3 Source reference presentation for CJK Unified ideographs . 37
24.4 Source references presentation for CJK Compatibility ideographs . 40
25 Source references for Tangut ideographs . 40
25.1 List of source references. 40
25.2 Source reference file for Tangut ideographs . 41
25.3 Source reference presentation for Tanguts ideographs . 42
26 Source references for Nüshu characters . 42
iv  © ISO/IEC 2020 – All rights reserved

26.1 List of source references. 42
26.2 Source reference file for Nüshu characters . 42
27 Character names and annotations . 43
27.1 Entity names . 43
27.2 Name formation . 43
27.3 Single name . 44
27.4 Name immutability . 44
27.5 Name uniqueness . 44
27.6 Character names for CJK ideographs . 45
27.7 Character names for Tangut ideographs . 45
27.8 Character names for Nüshu characters . 45
27.9 Character names for Khitan Small Script characters . 46
27.10 Character names for Hangul syllables . 46
28 Named UCS Sequence Identifiers . 47
29 Structure of the Basic Multilingual Plane .
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