ISO/IEC 10646:2017

Information technology - Universal Coded Character Set (UCS)

ISO/IEC 10646:2017 specifies the Universal Coded Character Set (UCS). It is applicable to the represen-tation, transmission, interchange, processing, storage, input, and presentation of the written form of the lan-guages of the world as well as of additional symbols. - specifies the architecture of this International Standard, - defines terms used in this International Standard, - describes the general structure of the UCS codespace, - specifies the Basic Multilingual Plane (BMP) of the UCS, - specifies supplementary planes of the UCS: the Supplementary Multilingual Plane (SMP), the Supplemen-tary Ideographic Plane (SIP), the Tertiary Ideographic Plane (TIP), and the Supplementary Special-purpose Plane (SSP), - defines a set of graphic characters used in scripts and the written form of languages on a world-wide scale, - specifies the names for the graphic characters and format characters of the BMP, SMP, SIP, TIP, SSP and their coded representations within the UCS codespace, - specifies the coded representations for control characters and private use characters, - specifies three encoding forms of the UCS: UTF-8, UTF-16, and UTF-32, - specifies seven encoding schemes of the UCS: UTF-8, UTF-16, UTF-16BE, UTF-16LE, UTF-32, UTF-32BE, and UTF-32LE, - specifies the management of future additions to this coded character set. The UCS is an encoding system different from that specified in ISO/IEC 2022. The method to designate UCS from ISO/IEC 2022 is specified in 12.2. A graphic character will be assigned only one code point in the standard, located either in the BMP or in one of the supplementary planes.

Technologies de l'information — Jeu universel de caractères codés (JUC)

Informacijska tehnologija - Univerzalni večoktetni nabor znakov (UCS)

General Information

• Status: Withdrawn
• Publication Date: 19-Dec-2017
• Withdrawal Date: 19-Dec-2017
• ICS: 35.040 - Information coding
• ICS: 35.040.10 - Coding of character sets
• Technical Committee: ISO/IEC JTC 1/SC 2 - Coded character sets
• Drafting Committee: ISO/IEC JTC 1/SC 2/WG 2 - Universal coded character set
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 21-Dec-2020
• Completion Date: 30-Oct-2025
• Ref Project: SIST ISO/IEC 10646:2018 - Information technology -- Universal Coded Character Set (UCS)

Relations

• Amended By: ISO/IEC 10646:2017/Amd 2:2019 - Information technology - Universal Coded Character Set (UCS) - Amendment 2: Nandinagari, Georgian extension, and other characters
• Effective Date: 18-Dec-2021
• Amended By: ISO/IEC 10646:2017/Amd 1:2019 - Information technology - Universal Coded Character Set (UCS) - Amendment 1: Dogra, Gunjala Gondi, Makasar, Medefaidrin, Indic Siyaq Numbers and other characters
• Effective Date: 07-Aug-2021
• Revised: ISO/IEC 10646:2020 - Information technology - Universal coded character set (UCS)
• Effective Date: 23-Apr-2020
• Revises: ISO/IEC 10646:2014/Amd 2:2016 - Information technology - Universal Coded Character Set (UCS) - Amendment 2: Bhaiksuki, Marchen, Tangut and other characters
• Effective Date: 30-Dec-2017
• Revises: ISO/IEC 10646:2014 - Information technology - Universal Coded Character Set (UCS)
• Effective Date: 05-Nov-2015

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 10646
Fifth edition
2017-12
Information technology — Universal
Coded Character Set (UCS)
Technologies de l'information — Jeu universel de caractères codés (JUC)
Reference number
©
ISO/IEC 2017
© ISO/IEC 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO/IEC 2017 – All rights reserved

CONTENTS
Foreword . vii
Introduction . viii
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 General structure of the UCS .9
6 Basic structure and nomenclature . 10
6.1 Structure . 10
6.2 Coding of characters . 11
6.3 Types of code points . 11
6.4 Naming of characters . 12
6.5 Short identifiers for code points (UIDs) . 12
6.6 UCS Sequence Identifiers . 13
6.7 Octet sequence identifiers . 13
7 Revision and updating of the UCS . 14
8 Subsets . 14
8.1 General . 14
8.2 Limited subset . 14
8.3 Selected subset. 14
9 UCS encoding forms . 14
9.1 General . 14
9.2 UTF-8 . 14
9.3 UTF-16 . 15
9.4 UTF-32 (UCS-4) . 16
10 UCS Encoding schemes . 16
10.1 General . 16
10.2 UTF-8 . 16
10.3 UTF-16BE . 16
10.4 UTF-16LE . 16
10.5 UTF-16 . 16
10.6 UTF-32BE . 17
10.7 UTF-32LE . 17
10.8 UTF-32 . 17
11 Use of control functions with the UCS . 17
12 Declaration of identification of features . 18
12.1 Purpose and context of identification . 18
12.2 Identification of a UCS encoding scheme . 19
© ISO/IEC 2017 – All rights reserved iii

12.3 Identification of subsets of graphic characters . 19
12.4 Identification of control function set . 19
12.5 Identification of the coding system of ISO/IEC 2022 . 20
13 Structure of the code charts and lists . 20
14 Block and collection names . 21
14.1 Block names . 21
14.2 Collection names . 21
15 Mirrored characters in bidirectional context . 21
15.1 Mirrored characters . 21
15.2 Directionality of bidirectional text . 21
16 Special characters . 22
16.1 General . 22
16.2 Space characters . 22
16.3 Currency symbols . 22
16.4 Format characters . 22
16.5 Ideographic description characters . 23
16.6 Variation selectors and variation sequences . 23
17 Presentation forms of characters . 24
18 Compatibility characters . 25
19 Order of characters . 25
20 Combining characters . 25
20.1 Order of combining characters . 25
20.2 Combining class and canonical ordering . 26
20.3 Appearance in code charts . 26
20.4 Alternate coded representations . 26
20.5 Multiple combining characters . 26
20.6 Collections containing combining characters . 27
20.7 Combining Grapheme Joiner . 27
21 Normalization forms. 27
22 Special features of individual scripts and symbol repertoires . 28
22.1 Hangul syllable composition method . 28
22.2 Features of scripts used in India and some other South Asian countries . 28
22.3 Byzantine musical symbols . 28
22.4 Source references for pictographic symbols . 29
23 Source references for CJK ideographs . 29
23.1 List of source references. 29
23.2 Source references file for CJK ideographs . 32
23.3 Source reference presentation for CJK Unified ideographs . 34
23.4 Source references presentation for CJK Compatibility ideographs . 37
24 Source references for Tangut ideographs . 37
24.1 List of source references. 37
24.2 Source reference file for Tangut ideographs . 38
24.3 Source reference presentation for Tanguts ideographs . 39
iv  © ISO/IEC 2017 – All rights reserved

25 Source references for Nüshu characters . 39
25.1 List of source references. 39
25.2 Source reference file for Nüshu characters . 39
26 Character names and annotations . 40
26.1 Entity names . 40
26.2 Name formation . 40
26.3 Single name . 41
26.4 Name immutability . 41
26.5 Name uniqueness . 41
26.6 Character names for CJK ideographs . 42
26.7 Character names for Tangut ideographs . 42
26.8 Character names for Nüshu characters . 42
26.9 Character names for Hangul syllables . 43
27 Named UCS Sequence Identifiers . 44
28 Structure of the Basic Multilingual Plane . 46
29 Structure of the Supplementary Multilingual Plane for scripts and symbols (SMP) . 48
30 Structure of the Supplementary Ideographic Plane (SIP) . 51
31 Structure of the Tertiary Ideographic Plane (TIP) . 51
32 Structure of the Supplementary Special-purpose Plane (SSP) . 51
33 Code charts and lists of character names . 52
33.1 General . 52
33.2 Code chart . 52
33.3 Character names list . 52
33.4 Summary of standardized variation sequences . 53
33.5 Code charts and lists of character names . 54
Annex A (normative) Collections of graphic characters for subsets . 2611
A.1 Collections of coded graphic characters . 2611
A.2 Blocks lists . 2617
A.3 Fixed collections of the whole UCS (except Unicode collections) . 2620
A.4 CJK collections. 2623
A.5 Other collections . 2624
A.6 Unicode collections . 2628
Annex B (normative) List of combining characters . 2629
Annex C (normative) Transformation format for planes 01 to 10 of the UCS (UTF-16) . 2630
Annex D (normative) UCS Transformation Format 8 (UTF-8) . 2631
Annex E (normative) Mirrored characters in bidirectional context . 2632
Annex F (informative) Format characters . 2633
F.1 General format characters . 2633
F.2 Script-specific format characters . 2635
F.3 Interlinear annotation characters . 2636
F.4 Subtending format characters . 2636
F.5 Shorthand format characters . 2637
F.6 Invisible mathematical operators . 2637
© ISO/IEC 2017 – All rights reserved v

F.7 Western musical symbols . 2637
F.8 Language tagging using Tag characters . 2638
Annex G (informative) Alphabetically sorted list of character names . 2640
Annex H (informative) The use of “signatures” to identify UCS . 2641
Annex I (informative) Ideographic description characters . 2642
I.1 General . 2642
I.2 Syntax of an ideographic description sequence . 2642
I.3 Individual definitions of the ideographic description characters . 2643
Annex J (informative) Recommendation for combined receiving/originating devices with internal
storage . 2645
Annex K (informative) Notations of octet value representations . 2646
Annex L (informative) Character naming guidelines . 2647
Annex M (informative) Sources of characters . 2650
Annex N (informative) External references to character repertoires . 2674
N.1 Methods of reference to character repertoires and their coding . 2674
N.2 Identification of ASN.1 character abstract syntaxes . 2674
N.3 Identification of ASN.1 character transfer syntaxes . 2675
Annex P (informative) Additional information on CJK Unified ideographs . 2676
Annex Q (informative) Code mapping table for Hangul syllables . 2679
Annex R (informative) Names of Hangul syllables . 2680
Annex S (informative) Procedure for the unification and arrangement of CJK ideographs . 2681
S.1 Unification procedure . 2681
S.2 Arrangement procedure . 2685
S.3 Source separation examples . 2685
S.4 Non-unification examples . 2690
Annex T (informative) Language tagging using Tag Characters . 2692
Annex U (informative) Characters in identifiers . 2693

vi  © ISO/IEC 2017 – All rights reserved

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commis-
sion) form the specialized system for worldwide standardization. National bodies that are members of ISO or
IEC participate in the development of International Standards through technical committees established by the
respective organization to deal with particular fields of technical activity. ISO and IEC technical committees
collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental,
in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have
established a joint technical committee, ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are described in
the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of
document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC
Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on the ISO
list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not constitute
an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade Organiza-
tion (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/fore-
word.html.
The committee responsible for this document is ISO/IEC JTC 1, Information technology, SC 2, Coded character
sets.
This fifth edition of ISO/IEC 10646 cancels and replaces the fourth edition (ISO/IEC 10646:2014), which has
been technically revised. It also incorporates ISO/IEC 10646:2014/Amd 1:2015 and ISO/IEC 10646:2014/Amd
2:2016.
This edition includes the following significant changes with respect to the previous edition:
• New scripts covered: Adlam, Bhaiksuki, , Marchen, Masaram Gondhi, Newa, Nushu, Osage, Soyombo, Tangut,
and Zanabazar Square,
• Existing scripts significantly extended: Cherokee, CJK Unified Ideographs (Extension F),
• New Emoji symbols.
© ISO/IEC 2017 – All rights reserved vii

Introduction
This International Standard specifies the Universal Coded Character Set (UCS). It is applicable to the represen-
tation, transmission, interchange, processing, storage, input and presentation of the written form of the lan-
guages of the world as well as additional symbols.
By defining a consistent way of encoding multilingual text it enables the exchange of data internationally. The
information technology industry gains data stability, greater global interoperability and data interchange. This
International Standard has been widely adopted in new Internet protocols and implemented in modern oper-
ating systems and computer languages. This edition covers over 130 000 characters from the world’s scripts.

viii  © ISO/IEC 2017 – All rights reserved

Information technology — Universal
Coded Character Set (UCS)
1 Scope
This International Standard specifies the Universal Coded Character Set (UCS). It is applicable to the represen-
tation, transmission, interchange, processing, storage, input, and presentation of the written form of the lan-
guages of the world as well as of additional symbols.
This International Standard
• specifies the architecture of this International Standard,
• defines terms used in this International Standard,
• describes the general structure of the UCS codespace,
• specifies the Basic Multilingual Plane (BMP) of the UCS,
• specifies supplementary planes of the UCS: the Supplementary Multilingual Plane (SMP), the Supplemen-
tary Ideographic Plane (SIP), the Tertiary Ideographic Plane (TIP), and the Supplementary Special-purpose
Plane (SSP),
• defines a set of graphic characters used in scripts and the written form of languages on a world-wide scale,
• specifies the names for the graphic characters and format characters of the BMP, SMP, SIP, TIP, SSP and
their coded representations within the UCS codespace,
• specifies the coded representations for control characters and private use characters,
• specifies three encoding forms of the UCS: UTF-8, UTF-16, and UTF-32,
• specifies seven encoding schemes of the UCS: UTF-8, UTF-16, UTF-16BE, UTF-16LE, UTF-32, UTF-32BE, and
UTF-32LE,
• specifies the management of future additions to this coded character set.
The UCS is an encoding system different from that specified in ISO/IEC 2022. The method to designate UCS from
ISO/IEC 2022 is specified in 12.2.
A graphic character will be assigned only one code point in the standard, located either in the BMP or in one of
the supplementary planes.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references, the
latest edition of the referenced document (including any amendments) applies.
ISO/IEC 2022:1994 Information technology — Character code structure and extension techniques.
ISO/IEC 6429:1992 Information technology — Control functions for coded character sets.
Unicode Standard Annex, UAX #9, The Unicode Bidirectional Algorithm:
http://www.unicode.org/reports/tr9/tr9-35.html
Unicode Standard Annex, UAX #15, Unicode Normalization Forms:
http://www.unicode.org/reports/tr15/tr15-44.html
Unicode Technical Standard, UTS #37, Ideographic Variation Database:
http://www.unicode.org/reports/tr37/tr37-8.html
© ISO/IEC 2017 – All rights reserved 1

Unicode Standard Version 9.0, Chapter 4, Character Properties
http://www.unicode.org/versions/Unicode9.0.0/ch04.pdf
Section 4.3, Combining Classes – Normative
Section 4.5, General Category – Normative
Section 4.7, Bidi Mirrored – Normative
Unicode Standard Version 9.0, Age Property:
http://www.unicode.org/Public/9.0.0/ucd/DerivedAge.txt
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
base character
graphic character which is not a combining character
Note 1 to entry – Most graphic characters are base characters. This sense of graphic combination does not preclude the presentation
of base characters from adopting different contextual forms or from participating in ligatures.
Note 2 to entry – A base character typically does not graphically combine with preceding characters. There are exceptions for some
complex writing systems.
3.2
Basic Multilingual Plane
BMP
plane 00 of the UCS codespace
3.3
block
contiguous range of code points to which a set of characters that share common characteristics, such as a script,
are allocated; a block does not overlap another block; one or more of the code points within a block may have
no character allocated to them
3.4
canonical form
form with which characters of this coded character set are specified using a single code point within the UCS
codespace
Note 1 to entry – The canonical form is not to be confused with an encoding form which describes the relationship between UCS code
points and one or several code units (see 3.23).
3.5
character
member of a set of elements used for the organization, control, or representation of textual data
Note 1 to entry – A graphic symbol can be represented by a sequence of one or several coded characters.
3.6
character boundary
(code unit sequence) demarcation between the last code unit of a coded character and the first code unit of the
next coded character
3.7
code chart
code table
rectangular array showing the representation of coded characters allocated within a range of the UCS codespace
2  © ISO/IEC 2017 – All rights reserved

3.8
coded character
association between a character and a code point
3.9
coded character set
set of coded characters
3.10
code point
code position
value in the UCS codespace
3.11
code unit
minimal bit combination that can represent a unit of encoded text for processing or interchange
Note 1 to entry – Examples of code units are octets (8-bit code units) used in the UTF-8 encoding form, 16-bit code units in the UTF-
16 encoding form, and 32-bit code units in the UTF-32 encoding form.
3.12
code unit sequence
CC-data-element
coded-character-data-element
element of interchanged information that is specified to consist of a sequence of code units, in accordance with
one or more identified standards for coded character sets
Note 1 to entry – Such sequence can contain code units associated with any type of code points.
Note 2 to entry – Since its second edition: ISO/IEC 10646:2011, this International Standard does not use implementation levels. Its
definition of code unit sequence corresponds to the former unrestricted implementation level 3. Other definitions of code unit se-
quence, previously known as level 1 and 2, are deprecated. To maintain compatibility with these previous editions, in the context of
identification of coded representation in International Standards such as ISO/IEC 8824 and ISO/IEC 8825, the concept of implemen-
tation level can still be referenced as ‘Implementation level 3’. See Annex N.
3.13
collection
numbered and named set of entities
Note 1 to entry – For a non extended collection, these entities consist only of those coded characters whose code points lie within
one or more identified ranges (see also 3.25 for extended collection).
Note 2 to entry – If any of the identified ranges include code points to which no character is allocated, the repertoire of the collection
will change if an additional character is assigned to any of those code points at a future amendment of this International Standard.
However, it is intended that the collection number and name will remain unchanged in future editions of this International Standard.
3.14
combining character
character which has General Category values of Spacing Combining Mark (Mc), Non Spacing Mark (Mn), and
Enclosing Mark (Me)
Note 1 to entry – These characters are intended for combination with the preceding non-combining graphic character, or with a
sequence of combining characters preceded by a non-combining character (see also 3.17).
3.15
combining class
value associated with each combining character determining its typographical interaction and its canonical or-
dering within a sequence of combining characters
3.16
compatibility character
graphic character included as a coded character of this International Standard primarily for compatibility with
existing coded character sets
© ISO/IEC 2017 – All rights reserved 3

3.17
composite sequence
sequence of graphic characters consisting of a base character followed by one or more combining characters,
ZERO WIDTH JOINER, or ZERO WIDTH NON-JOINER (see also 3.14)
Note 1 to entry – A graphic symbol for a composite sequence generally consists of the combination of the graphic symbols of each
character in the sequence.
Note 2 to entry – A composite sequence can be used to represent characters not encoded in the repertoire of this International Stand-
ard.
3.18
control character
control function the coded representation of which consists of a single code point
Note 1 to entry – Although control characters are often ‘named’ using terms such as DELETE, FORM FEED, ESC, these qualifiers do
not correspond to formal character names. See Clause 11 for a list of the long names used by ISO/IEC 6429 in association with the
control characters.
3.19
control function
action that affects the recording, processing, transmission, or interpretation of data, and that is represented by
a code unit sequence
3.20
decomposition mapping
mapping from a character to a sequence of one or more characters that is a canonical or compatibility equivalent
3.21
default state
state that is assumed when no state has been explicitly specified (see F.2.1, F.2.2, and F.2.3)
3.22
device
component of information processing equipment which can transmit and/or receive coded information within
code unit sequences
Note 1 to entry – It may be an input/output device in the conventional sense, or a process such as an application program or gateway
function.
3.23
encoding form
form that determines how each UCS code point for a UCS character is to be expressed as one or more code units
used by the encoding form
Note 1 to entry – This International Standard specifies UTF-8, UTF-16, and UTF-32.
3.24
encoding scheme
scheme that specifies the serialization of the code units from the encoding form into octets
Note 1 to entry – Some of the UCS encoding schemes have the same labels as the UCS encoding form. However, they are used in
different contexts. UCS encoding forms refer to in-memory and application interface representation of textual data. UCS encoding
schemes refer to octet-serialized textual data.
3.25
extended collection
collection for which the entities can also consist of sequences of code points that are in Normalization Form C
(NFC)
Note 1 to entry – Some collections such as 3 LATIN EXTENDED-A, 4 LATIN EXTENDED-B, 15 ARABIC EXTENDED, and many more,
have the term ‘extended’ in their name. This does not make them extended collections.
Note 2 to entry – See Clause 21 for discussion of Normalization Form C.
4  © ISO/IEC 2017 – All rights reserved

Note 3 to entry – The sequences of code points are typically referenced by Named UCS Sequence Identifiers (NUSI) (see Clause 27).
3.26
fixed collection
collection in which every code point within the identified range(s) has a character allocated to it, and which is
intended to remain unchanged in future editions of this International Standard
3.27
format character
character whose primary function is to affect the layout or processing of characters around it
Note 1 to entry – A format character generally does not have a visible representation of its own.
3.28
General Category
GC
value assigned to each UCS code point which determines its major class, such as letter, punctuation, and symbol
Note 1 to entry – Each value is defined as General Category property using a two-letter abbreviation in the Unicode Standard (see
reference to the current Unicode Standard General Category in 2).
Note 2 to entry – When referred as a group containing all GC values sharing the same first letter, the group may be described using
the first letter only. For example, ‘L’ stands for all letters ‘Lu’, ‘Ll’, ‘Lt’, ‘Lm’, and ‘Lo’.
3.29
graphic character
character, other than a control function or a format character, that has a visual representation normally hand-
written, printed, or displayed
3.30
graphic symbol
visual representation of a graphic character or of a composite sequence
3.31
high-surrogate code point
code point in the range D800 to DBFF reserved for the use of UTF-16
3.32
high-surrogate code unit
16-bit code unit in the range D800 to DBFF used in UTF-16 as the leading code unit of a surrogate pair (see 9.3)
3.33
ill-formed code unit sequence
UCS code unit sequence that purports to be in a UCS encoding form which does not conform to the specification
of that encoding form
EXAMPLE – An unpaired surrogate code unit is an ill-formed code unit sequence.
3.34
ill-formed code unit sequence subset
non-empty subset of a code unit sequence X which does not contain any code unit which also belong to any
minimal well-formed code unit sequence subset of X
Note 1 to entry – An ill-formed code unit sequence subset cannot overlap with a minimal well-formed code unit sequence.
3.35
interchange
transfer of character coded data from one user to another, using telecommunication means or interchangeable
media
Note 1 to entry – Interchange implies data serialization and the use of a UCS encoding scheme.
© ISO/IEC 2017 – All rights reserved 5

3.36
interworking
process of permitting two or more systems, each employing different coded character sets, to meaningfully in-
terchange character coded data
Note 1 to entry – Conversion between the two codes might be involved.
3.37
ISO/IEC 10646-1
former subdivision of ISO/IEC 10646 containing the specification of the overall architecture and the Basic Mul-
tilingual Plane (BMP)
Note 1 to entry – It is also referred to as Part 1 of ISO/IEC 10646.
Note 2 to entry – There are a first and a second Edition of ISO/IEC 10646-1.
3.38
ISO/IEC 10646-2
former subdivision of ISO/IEC 10646 containing the specification of the Supplementary Multilingual Plane
(SMP), the Supplementary Ideographic Plane (SIP) and the Supplementary Special-purpose Plane (SSP)
Note 1 to entry – It is also referred to as Part 2 of ISO/IEC 10646.
Note 2 to entry – There is only a first edition of ISO/IEC 10646-2.
3.39
low-surrogate code point
code point in the range DC00 to DFFF reserved for the use of UTF-16
3.40
low-surrogate code unit
16-bit code unit in the range DC00 to DFFF used in UTF-16 as the trailing code unit of a surrogate pair (see 9.3)
3.41
minimal well-formed code unit sequence
well-formed code unit sequence that maps to a single UCS scalar value
3.42
mirrored character
character whose image is mirrored horizontally in text that is laid out from right to left
3.43
octet
8-bit code unit
Note 1 to entry – The value is expressed in hexadecimal notation from 00 to FF in this International Standard (see Annex K).
3.44
plane
subdivision of the UCS codespace consisting of contiguous 65 536 code points beginning at a multiple of 65 536
which can be identified by a number from 00 to 10
Note 1 to entry – The UCS codespace contain 17 planes.
3.45
presentation
process of writing, printing, or displaying a graphic symbol
3.46
presentation form
(in the presentation of some scripts) form of a graphic symbol representing a character that depends on the
position of the character relative to other characters
6  © ISO/IEC 2017 – All rights reserved

3.47
private use plane
plane within this coded character set, the content of which is not specified in this International Standard
Note 1 to entry – Planes 0F and 10 are private use planes.
3.48
repertoire
specified set of characters that are represented in a coded character set
3.49
row
subdivision of a plane consisting of contiguous 256 code points beginning at a multiple of 256 which can be
identified by a number from 00 to FF
3.50
script
set of graphic characters used for the written form of one or more languages
3.51
supplementary plane
plane other than Plane 00 of the UCS codespace
Note 1 to entry – A supplementary plane accommodates characters which have not been allocated to the Basic Multilingual Plane.
3.52
Supplementary Multilingual Plane for scripts and symbols
SMP
plane 01 of the UCS codespace
3.53
Supplementary Ideographic Plane
SIP
plane 02 of the UCS codespace
3.54
Supplementary Special-purpose Plane
SSP
plane 0E of the UCS codespace
3.55
surrogate pair
representation for a single character that consists of a sequence of two 16-bit code units, where the first value
of the pair is a high-surrogate code unit and the second value is a low-surrogate code unit
3.56
Tertiary Ideographic Plane
TIP
plane 03 of the UCS codespace
3.57
UCS codespace
codespace consisting of the integers from 0 to 10FFFF (hexadecimal) available for assigning the repertoire of
the UCS characters
3.58
UCS scalar value
any UCS code point except high-surrogate and low-surrogate code points
© ISO/IEC 2017 – All rights reserved 7

3.59
unpaired surrogate code unit
code unit in a code unit sequence that is either a high-surrogate code unit that is not immediately followed by a
low-surrogate unit, or a low-surrogate code unit that is not immediately preceded by a high-surrogate code unit
3.60
user
person or other entity that invokes the service provided by a device
Note 1 to entry – This entity can be a process such as an application program if the “device” is a code converter or a gateway function.
3.61
well-formed code unit sequence
UCS code unit sequence that purports to be in a UCS encoding form which conforms to the specification of that
encoding form and contains no ill-formed code unit sequence subset
4 Conformance
4.1 General
Whenever private use characters are used as specified in this International Standard, the characters themselves
shall not be covered by these conformance requirements.
4.2 Conformance of information interchange
A code unit sequence (CC-data-element) within coded information for interchange is in conformance with this
International Standard if
a) all the coded representations of graphic characters within that code unit sequence conform to Clause 0, to
an identified encoding form chosen from Clause 9, and to an identified encoding scheme chosen from Clause
10;
b) all the graphic characters represented within that code unit sequence are taken from those wit
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