ISO/IEC 4873:1991

lSO/IEC
INTERNATIONAL
STANDARD 5 4873
Third edi tion
1991-12-15
---_
Information technology - ISO 8-bit code for
information interchange - Structure and rules
for implementation
Technologies de I ’informa tion - Code ISO 2 8 elements pour I ’echanqe
t.
d ’informa Gons - Structure et regles de mat&ialisation
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Reference numher
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.
ISO/IEC 4873:1991 (E)
Contents
Page
1
1 Scope
1
2 Conformance and implementation
1
2.1 Conformance
1
2.1.1 Conformance of information interchange
1
2.1.2 Conformance of devices
2
2.2 Implementation
2 l
3 Normative references
4 Definitions
4.1 active Position
4.2 bit combination
4.3 byte 2
2
4.4 Character
2
4.5 Character Position
2 /
4.6 coded-Character-data-element (CC-data-element)
3
4.7 coded Character set I
3
4.8 code extension
3
4.9 code table
3
4.10 control Character
3
4.11 control function
3
4.12 device
3
4.13 escape sequence
3
4.14 Final Byte
3 ~
4.15 graphic Character
4.16 graphic Symbol
4.17 repertoire
4.18 user 3
5 Notation, code tabie and names
5.1 Notation
5.2 Code table
5.3 Names
6 Structure of the 8-bit Code
4
6.1 Elements of the 8-bit code
5
6.2 Identification of the elements of the S-bit code
0 ISO/-IEc 1991
All rights reserved. No part of this publication may be reproduced or utiliz.ed in any form or by any
means, electronie or mechanical, including photocopying and microfilm, without Permission in
titing fkm the publisher.
ISO/IEC Copyright Ofke l Gase postale 56 l CH-121 1 Geneve 20 l Switzerland
Printed in Switzerkind
ii

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ISO/IEC 4873:1991 (E)
5
6.3 Invocation
6.3.1 CO set 5
5
Character SPACE
6.3.2
5
6.3.3 GO set
5
6.3.4 Character DELETE
6.3.5 Cl Set5
5
6.3.6 Gl set
5
6.3.7 G2 set
5
6.3.8 G3 set
5
7 Specification of the characters of the 8-bit code
6
7.1 CO set
6
7.2 Character ESCAPE
6
7.3 Character SPACE
6
7.4 GO set
9
7.5 Character DELETE
9
7.6 Cl set
9
7.7 Gl set
9
7.8 G2 set
10
7.9 G3 set
10
7.10 Summary of the specification of the %-bit code
10
8 Levels
10
8.1 Level 1
10
8.2 Level 2
11
8.3 Level 3
11
9 Version of the 8-bit code
11
9.1 Contents of a version
11
9.2 Unique coding of characters
11
10 Identification of version and level
11
10.1 Purpose and context of identification
12
10.2 ldentification of level
12
10.3 Identification of a version
12
10.4 Switching from one version to another
12
10.5 Switching from one Level to another
Annexes
16
A Restrittions applicable to the CO and Cl sets
17
B Shift functions
18
Composite graphic characters
C
. . .
111

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ISO/IEC 4873:1991 (E)
<
Use of bit combinations 00/14 and 00/15
D 19
E Main differentes between the 2nd edition (1986) and the present (third) edition of this International
Standard 19

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ISO/IEC 4873 : 1991 (E)
Foreword
ISO (the International Organization for Standardization) and IEC (the
International Electrotechnical Commission) 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-govemmental, 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. Draft International Standards adopted by
the joint technical committee are circulated to national bodies for voting.
Publication as an International Standard requires approval by at least 75 % of
the national bodies casting a vote.
International Standard ISO/IEC 4873 was prepared by Joint Technical
Committee ISO/IEC JTC 1, Information lechnology.
This third edition cancels and replaces the second cdition (ISO 4873 : 1986),
which has been technically revised.
Annex A forms an integral part of this International Standard. Annexes B, C, D
and E are for information only.

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ISO/IEC 487.3 : 1991 (E)
INTERNATIONAL STANDARD
ISO 8-bit Code fo,r information
Information technology -
interchange - Structure and rules for implementation
1 Scope
This International Standard specifies an 8-bit code derived from, and compatible with, the 7-bit coded
Character set specified in ISO/IEC 646.
The characteristics of this code are also in conformance with the Code extension techniques specified in
ISO 2022.
This International Standard specifies an 8-bit code with a number of Options. It also provides guidance on
how to exercise the Options to define specific Versions.
This code is primarily intended for general information interchange within an &-bit environment among
data processing Systems and associated equipment, and within data communication Systems. The need for
graphic characters and control functions in data processing has also been taken into account.
The code includes the 10 digits as well as the 52 small and capital ietters of the basic Latin alphabet and
may include accented letters, special Latin letters and/or the letters of one or several non-Latin alphabet(s).
2 Conformance and implementation
2.1 Conformance
2.1.1 Conformance of information interchange
A coded-Character-data-element (CC-data-element) within coded information for interchange is in
conformance with a version of this International Standard if all the codecl representations of characters
within that CC-data-element conform to the requirements of clause 9.
A Claim of conformance shall identify the Version adopted.
2.1.2 Conformance of devices
A device is in conformance with this International Standard if it conforms to the requirements of 2.1.2.1,
and either or both of 2.1.2.2 and 2.1.2.3. A Claim of conformance shall identify the document which
contains the description specified in 2.1.2.1, and shall identify the version adopted.
2.1.2.1 Device description
A device that conforms to this International Standard shall be the subject of a description that identifies
the means by which the user may supply characters to the device, or may recognize them when they are
made available to him, as specified respectively in 2.1.2.2 and 2.1.2.3.
2.1.2.2 Originating devices
An originating device shall allow its user to supply any sequence of characters from the version adopted,
and shall be capable of transmitting their coded representations within a CC-data-eiement.
1 ’

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ISO/IEC 4873:1991 (E)
2.1.2.3 Receiving devices
A receiving device shall be capable of receiving and interpreting any coded representations of characters
that are within a CC-data-element, and that conform to 2.1.1, and shall make the corresponding characters
available to its user in such a way that the user tan identify them from among those of the version
adopted, and tan distinguish them from each other.
2.2 Implementation
The use of this code requires definitions of its implementation in various media. For example, these could
include punched tapes, punched cards, magnetic and Optical media and transmission channels, thus
permitting interchange of data to take place either indirectly by means of an intermediate recording in a
physical medium, or by local connection of various units (such as input and output devices and Computers)
or by means of data transmission equipment.
The implementation of this code in physical media and for transmission, taking into
account the need for
error checking, is the subject of other International Standards.
3 Normative references
The following Standards contain provisions which, through reference in this text, constitute provisions of
this International Standard. At the time of publication, the editions indicated were valid. All Standards are
subject to revision, and Parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the Standards listed below. Members of
IEC and ISO maintain registers of currently valid International Standards.
ISO/IEC 646: 1991 lnformation technology - /SO 7-bit coded Character set for information interchange.
ISO 2022: 1986 Information processing - ISO 7-bit and S-bit coded Character sets - Code extension
techniques.
ISO/IEC 6429: ‘) Information technology - Control functions for 7-bit and g-bit coded Character Sets.
ISO/IEC 10367: 1991 Information technology -
Standardized coded graphic Character sets for use in g-bit
Codes.
ISO International Register of Coded Character Sets to be Used with Escape Sequences (ISO 2375).
4 Definitions
For the purpose of this International Standard the following definitions apply.
4.1 active Position : The Character Position which is to image the graphic Symbol representing the next
graphic Character or relative to which the next control function is to be executed.
NOTE - In general, the active position is indicated in a display by a cursor.
4.2 bit combination : An ordered set of bits used for the representation of characters.
4.3 byte : A bit string that is operated upon as a unit.
4.4 Character : A member of a set of elements used for the organization, control or representation of data.
The Portion of a display that is imaging or is capable of imaging a graphic Symbol.
4.5 Character Position :
An element of interchanged information that is
4.6 coded-Character-data-element (CGdata-element) :
specified to consist of a sequence of coded representations of characters, in accordance with one or more
identified Standards for coded Character Sets.
1) To be published.
2

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ISO/IEC 4873:1991 (E)
NOTES
1. In a communication environment according to the Reference Model for Open Systems Interconnection (ISO 7499, a
CC-data-element will form all or part of the information that corresponds to the Presentation-Protocol-Data-Unit
(PPDU) defined in that International Standard.
3
&. When i nform ation interchange is accomplished means of i n terc hangeable media, a CC-data-elemen t will form all
bY
or part of the in formation that corresponds to the use r data, and not t hat recorded during formatting and initia lization.
4.7 coded Character set; code : A set of unam big uous rules that establishes a Character set and the one-to-
one relatio nship between the ch aracters of the set and their bit combinations.
4.8 code extension : The techniques for the encoding of characters that are not included in the Character
set of a given Code.
4.9 table : A table showi ng the characte r al located to each bit combination in a Code.
4.10 control Character : A control function the coded
representation of which consists of a Single bit
combination.
4.11 control function : An action that affects the recording, or interpretation of
processing, transmission,
data, and that has a coded representation consisting of one or more bit combinations.
4.12 device : A component of information receive, coded
processing equipment which tan transmit, and/or
information within CC-data-elements.
NOTE - It may be an input/output device in the conventional sense, or a process such as an application program or
gateway function.
4.13 escape sequence A string of bit combinations that is used for control purposes in code extension
procedures. The first of these bit combinations represents the control function ESCAPE.
4.14 Final Byte : The bit combination that terminates an escape sequence or a control sequence.
4.15 graphic Character : A Character, other than a control function, that has a visual representation
normally handwritten, printed or displayed, and that has a coded representation consisting of one or more
bit combinations.
4.16 graphic Symbol : A visual representation of a graphic Character or of a control function.
of one or bit
4.17 repertoire : A specified set of characters that are represented by means
combinations of a coded Character set.
4.18 user : A person or other entity that invokes the Services provided by a device.
NOTES
“device” is a code convertor or a gateway
1. This entity may be a process such as an application program if the
function, for example.
to him, may be in the form of Codes local to the device, or
2. The characters, as supplied by* the user or made availabie
1.2 above is satisfied.
of non -conventional visible representations, provided that 2.
5 Notation, code table and names
5.1 Notation
The bits of the bit combinations of the 8-bit code are identified by bs, b7, bg, b5, b4, b3, b2 and bl, where
bs is the highest-Order, or most-significant bit, and bl is the lowest-Order, or least-significant, bit.
in the range 0 to 255 in binary notation by
The bit combinations may be interpreted to represent integers
attributing the following weights to the individual bits:

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ISO/IEC 4873:1991 (E)
,
l
.
b b b
Bit
b8 7 b6 b5 4 b3 b2 1
I
Weight 128 64 32 16 8 4 2 1
\
In this International Standard, the bit combinations are identified by notations of the form xx/yy, where xx
and yy are numbers in the range 00 to 15. The correspondence between the notations of the form xx/yy
and the bit combinations consisting of the bits bg to bl, is as foliows:
- xx is the number represented by b8, b7, bh and b5 where these bits are given the weights 8, 4, 2
and 1 respectively;
- yy is the number represented by b+ b3, b2 and bl where these bits are given the weights 8, 4, 2
and 1 respectively.
The notations of the form xx/yy are the same as the ones used to identify code table positions, where xx is
the column number and yy is the row number (see 5.2).
5.2 Code table
An 8-bit code table consists of 256 positions arranged in 16 columns and 16 rows. The columns and rows
are numbered 00 to 15.
The code table positions are identified by notations of the form xx/yy, where xx is the column number and
yy is the row number.
The positions of the code table are in one-to-one correspondence with the bit combinations of the Code.
The notation of a code table Position, of the form xx/yy, is the same as that of the corresponding bit
combination.
5.3 Names
This International Standard assigns one name to each Character. In addition, it specifies an acronym for
control characters and for the characters SPACE and DELETE, and a graphic Symbol for each graphic
Character. By convention, only capital letters, and hyphen are used for writing the names of the characters.
For acronyms only capital letters, space and digit are used. It is intended that the acronyms and this
convention be retained in all translations of the text.
The names Chosen to denote graphic characters are intended to reflect their customary meaning. However,
this International Standard does not define and does not restritt the meanings of graphic characters.
Neither does it specify a particular style or font design for the graphic characters when imaged.
6 Structure of the 8-bit code
6.1 Elements of the 8-bit code
The 8-bit code consists of the following Parts (see figure 1).
A CO set
4
A set of up to 30 control characters represented by bit combinations OO/OO to 01/15,
except 00/14 and 00115 which shall be unused.
The Character SPACE
b)
A graphic Character represented by bit combination O2/OO.
A CO set
4
A set of 94 graphic characters represented by bit combinations 02/01 to 07/14.

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ISO/IEC 4873:1991 (E)
The Character DELETE
4
A Character represented by bit combination 07115.
A Cl set
e)
A set of up to 32 control characters represented by bit combinations 08/00 to 09115.
A Gl set
f )
A set of up to 96 graphic characters represented by bit combinations lO/OO to W15.
A G2 set
g)
A set of up to 96 graphic characters.
A G3 set
hl
A set of up to 96 graphic characters.
6.2 Identification of the elements of the 8-bit code
The method of identification of the code elements listed in 6.1 is specified in clause 10.
6.3 Invocation
6.3.1 CO set
The identification of the CO set also invokes that set.
6.3.2 Character SPACE
The Character SPACE shall be represented by bit combination 02/00. It is not explicitly invoked.
6.3.3 GO set
The GO set shall be as specified in 7.4. It is not explicitly invoked.
6.3.4 Character DELETE
The Character DELETE shall be represented by bit combination 07/15. It is not explicitly invoked.
6.3.5 Cl set
The identification of the Cl set also invokes that set.
6.3.6 Gl set
The identification of the Gl set also invokes that set. The locking-shift function LSlR shall also invoke the
Gl set.
6.3.7 G2 set
Either the set as a whole shall be invoked by the locking-shift function LS2R (see annex B) into columns
10 to 15, or individual characters of it shall be invoked by means of the Single-shift function SS2, (see 7.6).
6.3.8 G3 set
Either the set as a whole shall be invoked by the locking-shift function LS3R (see annex B) into columns
10 to 15, or individual characters of the set shall be invoked by means of the Single-shift function SS3 (see
. .
7 6)
7 Specification of the characters of the 8-bit code
The use of control functions such as BACKSPACE or CARRIAGE RETURN, for the coded representation
of composite characters is prohibited by this International Standard (see annex C).

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ISO/IEC 4873:1991 (E)
7.1 CO set
The requirements for the CO set are
- bit combinations 00114 and 00/15 shall not be used (see annex D);
- the control Character ESCAPE shall be represented by bit combination Ol/ll;
- any control characters tan be allocated to the other bit combinations subject to the restrictions
specified in annex A.
NOTE - A CO set comprising only ESCAPE represented by bit combination 01/11 has been registered (Registration
ISO-IR No. 104), and is identified by ESC 02/01 04/07.
7.2 Character ESCAPE
ESCAPE is a control Character used to form escape sequences. In this International Standard the use of
escape sequences is specified in clause 10.
Table 1 - ESCAPE
COded
Acronym
Name
representation
I
ESCAPE Ol/ll
ESC
-4
7.3 Character SPACE
A graphic Character having a visual representation consisting of the absence of a graphic Symbol. It Causes
the active Position to be advanced by one Character Position.
Table 2 - SPACE
.
Coded
Acronym Name
representation
SPACE 02/00
SP
7.4 GO set
The 94 bit combinations 02/01 to 07/14 are used to represent graphic characters. All graphic characters
allocated to bit combinations in the range 02/01 to 07/14 are spacing characters, that is they Cause the
active Position to advance by one Character Position. The graphic characters allocated by this International
Standard to these 94 bit combinations are specified in table 3.

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ISO/IEC 4873:1991 (E)
Table 3 - Graphit characters of the GO set
-
Graphit
COded
Name
Symbol
representation
! EXCLAMATION MARK
02/01
II
QUOTATION MARK '
02/02
# NUMBER SIGN
02/03
$ DOLLAR SIGN 02/04
0
0 / PERCENT SIGN 02/05
& AMPERSAND 02/06
I APOSTROPHE 02/07
LEFT PARENTHESIS
02/08
(
1 RIGHT PARENTHESIS 02/09
* ASTERISK 02/10
+
PLUS SIGN
02/11
9 COMMA 02/12
HYPHEN-MINUS 02113
0 FULL STOP 02/14
/ SOLIDUS 02/15
0 DIGIT ZERO 03/00
1 ’ DIGIT ONE 03/01
2 DIGIT TWO 03/02
3 DIGIT THREE 03/03
4 DIGIT FOUR 03/04
5 DIGIT FIVE 03/05
6 DIGIT SIX 03/06
7 DIGIT SEVEN 03/07
8 DIGIT EIGHT 03/08
9 DIGIT NINE 03/09
l
0 COLON 03/10
0 SE
...