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1、BRITISH STANDARD BS ISO/IEC 646:1991 Incorporating Amendment No. 1 Implementation of ISO/IEC 646:1991 Information technology ISO 7-bit coded character set for information interchange UDC 681.3.04:681.327.1 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled C
2、opy, (c) BSI BS ISO/IEC 646:1991 This British Standard, having been prepared under the direction of the Information Systems Technology Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 28 February 1992 BSI 10-1999 The following BSI referenc
3、es relate to the work on this standard: Committee reference IST/2 Draft for comment 90/62175 DC ISBN 0 580 20672 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Information Systems Technology Standards Policy Committee (IST/-) to Techn
4、ical Committee IST/2, upon which the following bodies were represented: British Computer Society British Federation of Printing Machinery and Supplies Ltd. British Telecommunications plc Digital Equipment Co Ltd. IBM United Kingdom Ltd. Information and Communications Industry Association Institution
5、 of Electrical Engineers International Computers Limited Philips Research Laboratories Coopted members Amendments issued since publication Amd. No.DateComments 7619February 1993 Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Unco
6、ntrolled Copy, (c) BSI BS ISO/IEC 646:1991 BSI 10-1999i Contents Page Committees responsibleInside front cover National forewordii Forewordiv Text of ISO/IEC 6461 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO/IEC 646:1991 ii BSI 10-
7、1999 National foreword This 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
8、 of the Information Systems 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 inform
9、ed; monitor related international 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
10、the necessary provisions of 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 i
11、i, the ISO/IEC title page, pages ii to iv, pages 1 to 14 and a back 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. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:
12、46:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO/IEC 646:1991 (E) ii BSI 10-1999 Contents Page Forewordiv 1Scope1 2Conformance and implementation1 2.1Conformance1 2.1.1Conformance of inform
13、ation interchange1 2.1.2Conformance of devices1 2.2Implementation1 3Normative references2 4Definitions2 4.1active position2 4.2bit combination2 4.3character2 4.4character position2 4.5coded character set2 4.6coded-character-data-element (CC-data-element)2 4.7code extension2 4.8code table2 4.9control
14、 character3 4.10control function3 4.11device3 4.12escape sequence3 4.13Final byte3 4.14graphic character3 4.15graphic symbol3 4.16repertoire3 4.17user3 5Notation, code table and names3 5.1Notation3 5.2Code table4 5.3Names4 6Specification of the coded character set4 6.1Structure4 6.2Control character
15、s5 6.3Character SPACE5 6.4Graphic characters5 6.4.1Unique graphic character allocations5 6.4.2Alternative graphic character allocations7 6.4.3National or application-oriented graphic character allocations8 6.5Character DELETE8 7Composite graphic characters8 8Versions of the coded character set8 8.1G
16、eneral8 8.2International Reference Version (IRV)9 8.3National versions9 8.4Application-oriented versions9 9Identification of versions10 9.1Purpose and context of identification10 9.2Identification of a version10 10Explanation of Code Table 4 and Table 510 Licensed Copy: sheffieldun sheffieldun, na,
17、Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO/IEC 646:1991 (E) BSI 10-1999iii Page Annex A (normative) Specification of the C0 set13 Annex B (informative) Guidelines for standards derived from ISO/IEC 64614 Annex C (informative) Differences between the second edition (1983) and
18、the present (third) edition of this International Standard14 Figure 1 Structure of the 7-bit coded character set5 Table 1 Unique graphic character allocations6 Table 2 Alternative graphic character allocations8 Table 3 IRV graphic character allocations9 Table 4 Basic code table11 Table 5 Version wit
19、h the G0 set of the IRV12 Table A.1 C0 set of ISO/IEC 642913 Descriptors: Data processing, information interchange, character sets, coded character sets, ISO seven-bit codes, control characters, graphic characters. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncon
20、trolled Copy, (c) BSI ISO/IEC 646:1991 (E) iv BSI 10-1999 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
21、 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
22、-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. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting
23、. Publication as an International Standard requires approval 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
24、:1983) which has been technically revised. Annex A forms an integral part of this International Standard. Annex B and Annex C are for information only. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO/IEC 646:1991 (E) BSI 10-19991 1 Scope
25、 This International Standard specifies a set of 128 characters, (control characters and graphic characters such as letters, digits and symbols) with their coded representation. Most of these characters are mandatory and unchangeable, but provision is made for some flexibility to accommodate national
26、 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 options to define specific national versions and application-oriented versions. Furthermore it specifies the International Reference V
27、ersion (IRV) in which such options have been exercised. This character set is primarily intended for the interchange of information among data processing systems and associated equipment, and within data communication systems. The need for graphic characters and control functions in data processing
28、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 of control characters for code extension where its character set is insufficient for particular applications. Procedures for the us
29、e of these control characters are specified in ISO 2022. The definitions of the control characters mentioned in this International Standard are specified in ISO 6429. It is assumed that data associated with them are to be processed serially in a forward direction. When they are included in strings o
30、f 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 effects or may require additional special treatment to ensure that they result in their desired function. 2 Conformance and implemen
31、tation 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 this International Standard if all the coded representations of characters within that CC-data-element conform to the r
32、equirements of 8.1 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 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.
33、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 be the subject of a description that identifies the means by which the user may supply characters to the device, or may recognize
34、 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
35、 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-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
36、 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 definitions of its implementation in various media. For example, these could include punched tapes, punched cards, magnetic and optical
37、 interchangeable media and transmission channels, thus permitting interchange of data to take place either indirectly by means of an intermediate recording on a physical medium, or by local connection of various units (such as input and output devices and computers) or by means of data transmission
38、equipment. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO/IEC 646:1991 (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 checking, is the subj
39、ect 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, a
40、nd 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, Information processing
41、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 sets1). 4 Definitions For the purpose of this International Standard the following definitions apply. 4.1 active position the character posit
42、ion 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 representation of cha
43、racters 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 that establishes a chara
44、cter 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 accordance with one o
45、r 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 Unit (PPDU) defined in
46、 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 extension the techniq
47、ues 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. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 21 09:46:49 GMT+00:00 2006, Uncontrolled Copy
48、, (c) BSI ISO/IEC 646:1991 (E) BSI 10-19993 4.9 control character a control function the 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 representa
49、tion consisting of one or more bit combinations 4.11 device a component of information processing 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 control purposes in code extension procedures. The first of these bit combinations represents the control function ESCAPE 4.13 final byte the bit combination that t