1、BRITISH STANDARD BS ISO/IEC 646:1991 Incorporating Amendment No. 1 Implementation of ISO/IEC 646:1991 Information technology ISO7-bit coded character set for information interchange UDC 681.3.04:681.327.1BSISO/IEC646:1991 This British Standard, having been prepared under the directionof the Informat
2、ion Systems Technology Standards Policy Committee, was publishedunder the authority ofthe Standards Board and comesinto effect on 28 February 1992 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference IST/2 Draft for comment 90/62175 DC ISBN 0 580 20672 6
3、Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Information Systems Technology Standards Policy Committee (IST/-) to Technical Committee IST/2, upon which the following bodies were represented: British Computer Society British Federation
4、 of Printing Machinery and Supplies Ltd. British Telecommunications plc Digital Equipment Co Ltd. IBM United Kingdom Ltd. Information and Communications Industry Association Institution of Electrical Engineers International Computers Limited Philips Research Laboratories Coopted members Amendments i
5、ssued since publication Amd. No. Date Comments 7619 February 1993 Indicated by a sideline in the marginBSISO/IEC646:1991 BSI 10-1999 i Contents Page Committees responsible Inside front cover National foreword ii Foreword iv Text of ISO/IEC 646 1BSISO/IEC646:1991 ii BSI 10-1999 National foreword This
6、 British Standard reproduces verbatim ISO/IEC 646:1991 and implements it as the base standard from which the UK national version of the code is derived (see BS 4730:1993 Specification for UK 7-bit coded character set). This British Standard is published under the direction of the Information Systems
7、 Technology Standards Policy Committee whose Technical Committee IST/2 has the responsibility to: aid enquirers to understand the text; present to the responsible international committee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related interna
8、tional and European developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from BSI Sales Department, BSI, Linford Wood, Milton Keynes, MK14 6LE. A British Standard does not purport to include all the necessary provisions of
9、 a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theISO/IEC title page, p
10、ages ii to iv, pages 1 to 14 andaback cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.ISO/IEC646:1991(E) ii BSI 10-1999 Contents Page Foreword iv 1 Scope 1 2 Conformance and i
11、mplementation 1 2.1 Conformance 1 2.1.1 Conformance of information interchange 1 2.1.2 Conformance of devices 1 2.2 Implementation 1 3 Normative references 2 4 Definitions 2 4.1 active position 2 4.2 bit combination 2 4.3 character 2 4.4 character position 2 4.5 coded character set 2 4.6 coded-chara
12、cter-data-element (CC-data-element) 2 4.7 code extension 2 4.8 code table 2 4.9 control character 3 4.10 control function 3 4.11 device 3 4.12 escape sequence 3 4.13 Final byte 3 4.14 graphic character 3 4.15 graphic symbol 3 4.16 repertoire 3 4.17 user 3 5 Notation, code table and names 3 5.1 Notat
13、ion 3 5.2 Code table 4 5.3 Names 4 6 Specification of the coded character set 4 6.1 Structure 4 6.2 Control characters 5 6.3 Character SPACE 5 6.4 Graphic characters 5 6.4.1 Unique graphic character allocations 5 6.4.2 Alternative graphic character allocations 7 6.4.3 National or application-oriente
14、d graphic character allocations 8 6.5 Character DELETE 8 7 Composite graphic characters 8 8 Versions of the coded character set 8 8.1 General 8 8.2 International Reference Version (IRV) 9 8.3 National versions 9 8.4 Application-oriented versions 9 9 Identification of versions 10 9.1 Purpose and cont
15、ext of identification 10 9.2 Identification of a version 10 10 Explanation of Code Table 4 and Table 5 10ISO/IEC646:1991(E) BSI 10-1999 iii Page Annex A (normative) Specification of the C0 set 13 Annex B (informative) Guidelines for standards derived from ISO/IEC 646 14 Annex C (informative) Differe
16、nces between the second edition (1983) and the present (third) edition of this International Standard 14 Figure 1 Structure of the 7-bit coded character set 5 Table 1 Unique graphic character allocations 6 Table 2 Alternative graphic character allocations 8 Table 3 IRV graphic character allocations
17、9 Table 4 Basic code table 11 Table 5 Version with the G0 set of the IRV 12 Table A.1 C0 set of ISO/IEC 6429 13 Descriptors: Data processing, information interchange, character sets, coded character sets, ISO seven-bit codes, control characters, graphic characters.ISO/IEC646:1991(E) iv BSI 10-1999 F
18、oreword 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 technic
19、al 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
20、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 approva
21、l by at least 75 % of the national bodies casting a vote. International Standard ISO/IEC 646 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology. This third edition cancels and replaces the second edition (ISO 646:1983) which has been technically revised. Annex A forms an
22、 integral part of this International Standard. Annex B and Annex C are for information only.ISO/IEC646:1991(E) BSI 10-1999 1 1 Scope This International Standard specifies a set of 128 characters, (control characters and graphic characters such as letters, digits and symbols) with their coded represe
23、ntation. Most of these characters are mandatory and unchangeable, but provision is made for some flexibility to accommodate national and other requirements. This International Standard specifies a 7-bit coded character set with a number of options. It also provides guidance on how to exercise the op
24、tions to define specific national versions and application-oriented versions. Furthermore it specifies the International Reference Version (IRV) in which such options have been exercised. This character set is primarily intended for the interchange of information among data processing systems and as
25、sociated equipment, and within data communication systems. The need for graphic characters and control functions in data processing has also been taken into account in determining this character set. This character set is applicable to alphabets of the Latin script. This character set allows the use
26、 of control characters for code extension where its character set is insufficient for particular applications. Procedures for the use of these control characters are specified in ISO 2022. The definitions of the control characters mentioned in this International Standard are specified in ISO6429. It
27、 is assumed that data associated with them are to be processed serially in a forward direction. When they are included in strings of data which are processed other than serially in a forward direction or when they are included in data formatted for fixed-record processing they may have undesirable e
28、ffects or may require additional special treatment to ensure that they result in their desired function. 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 confo
29、rmance with this International Standard if all the coded representations of characters within that CC-data-element conform to the requirements of8.1 of this International Standard. A claim of conformance shall identify the version adopted in accordance with 8.2 to 8.4. 2.1.2 Conformance of devices A
30、 device is in conformance with this International Standard if it conforms to the requirements of2.1.2.1, and either or both of 2.1.2.2 and 2.1.2.3 below. A claim of conformance shall identify the version adopted. 2.1.2.1 Device description A device that conforms to this International Standard shall
31、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 supp
32、ly any sequence of characters from the version adopted, and shall be capable of transmitting their coded representations within a CC-data-element. 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-
33、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 can identify them from among those of the version adopted, and can distinguish them from each other. 2.2 Implementation The use of this character set requires defini
34、tions of its implementation in various media. For example, these could include punched tapes, punched cards, magnetic and optical interchangeable media and transmission channels, thus permitting interchange of data to take place either indirectly by means of an intermediate recording on a physical m
35、edium, or by local connection of various units (such as input and output devices and computers) or by means of data transmission equipment.ISO/IEC646:1991(E) 2 BSI 10-1999 The implementation of this coded character set in physical media and for transmission, taking into account the need for error ch
36、ecking, 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 sub
37、ject 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 2022:1986, Info
38、rmation processing ISO 7-bit and 8-bit coded character sets Code extension techniques. ISO/IEC 6429, Information processing Control functions for 7-bit and 8-bit coded character sets 1) . 4 Definitions For the purpose of this International Standard the following definitions apply. 4.1 active positio
39、n 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 1In general, the active position is indicated in a display by a cursor. 4.2 bit combination an ordered set of bits used for the
40、representation of characters 4.3 character a member of a set of elements used for the organization, control or representation of data 4.4 character position the portion of a display that is imaging or is capable of imaging a graphic symbol 4.5 coded character set; code a set of unambiguous rules tha
41、t establishes a character set and the one-to- one relationship between the characters of the set and their bit combinations 4.6 coded-character-data-element (CC-data-element) an element of interchanged information that is specified to consist of a sequence of coded representations of characters, in
42、accordance with one or more identified standards for coded character sets NOTE 2In a communication environment according to the Reference Model for Open Systems Interconnection (ISO 7498), a CC-data-element will form all or part of the information that corresponds to the Presentation Protocol Data U
43、nit (PPDU) defined in that International Standard. NOTE 3When information interchange is accomplished by means of interchangeable media, a CC-data-element will form all or part of the information that corresponds to the user data, and not that recorded during formatting and initialization. 4.7 code
44、extension the techniques for the encoding of characters that are not included in the character set of a given code 4.8 code table a table showing the character allocated to each bit combination in a code 1) To be published.ISO/IEC646:1991(E) BSI 10-1999 3 4.9 control character a control function the
45、 coded representation of which consists of a single bit combination 4.10 control function an action that affects the recording, processing, transmission, or interpretation of data, and that has a coded representation consisting of one or more bit combinations 4.11 device a component of information p
46、rocessing equipment which can transmit, and/or receive, coded information within CC-data-elements NOTE 4It may be an input/output device in the conventional sense, or a process such as an application program or gateway function. 4.12 escape sequence a string of bit combinations that is used for cont
47、rol purposes in code extension procedures. The first of these bit combinations represents the control function ESCAPE 4.13 final byte the bit combination that terminates an escape sequence or a control sequence 4.14 graphic character a character, other than a control function, that has a visual repr
48、esentation normally handwritten, printed or displayed, and that has a coded representation consisting of one or more bit combinations 4.15 graphic symbol a visual representation of a graphic character or of a control function 4.16 repertoire a specified set of characters that are represented by mean
49、s of one or more bit combinations of a coded character set 4.17 user a person or other entity that invokes the services provided by a device NOTE 5This entity may be a process such as an application program if the “device” is a code convertor or a gateway function, for example. NOTE 6The characters, as supplied by the user or made available to him, may be in the form of codes local to the device, or of non-conventional visible representations, provided that2.1.2 above is satisfied. 5 Notation, code table and names 5.1 Notation The bits of the
