1、BRITISH STANDARD BS ISO/IEC 4873:1991 Implementation of ISO/IEC 4873:1991 Information technology ISO 8-bit code for information interchange Structure and rules for implementationBSISO/IEC 4873:1991 This British Standard, having been prepared under the directionof the Information Systems Technology S
2、tandardsPolicy Committee, waspublishedunder the authorityofthe Standards Boardand comes into effect on 28 February 1992 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference IST/2 Draft for comment 90/62173 DC ISBN 0 580 20671 8 Committees responsible for
3、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 of Printing Machinery and
4、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 issued since publication Amd
5、. No. Date CommentsBSISO/IEC 4873:1991 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword iv Text of ISO/IEC 4873 1BSISO/IEC 4873:1991 ii BSI 01-2000 National foreword This British Standard reproduces verbatim ISO/IEC4873:1991 and implements it as the
6、 UK national standard. This British Standard is published under the direction 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 enqui
7、ries on interpretation, or proposals for change, and keep UK interests informed; 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,
8、 Milton Keynes, MK146LE. A British Standard does not purport to include all 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
9、 This document comprises a front cover, an inside front cover, pagesi andii, theISO/IEC title page, pages ii to iv, pages1 to14 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
10、front cover.ISO/IEC 4873:1991(E) ii BSI 01-2000 Contents Page Foreword iv 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 1 2.2 Implementation 1 3 Normative references 1 4 Definitions 2 4.1 active position 2 4
11、.2 bit combination 2 4.3 byte 2 4.4 character 2 4.5 character position 2 4.6 coded-character-data-element (CC-data-element) 2 4.7 coded character set 2 4.8 code extension 2 4.9 code table 2 4.10 control character 2 4.11 control function 2 4.12 device 2 4.13 escape sequence 2 4.14 Final Byte 2 4.15 g
12、raphic character 2 4.16 graphic symbol 3 4.17 repertoire 3 4.18 user 3 5 Notation, code table and names 3 5.1 Notation 3 5.2 Code table 3 5.3 Names 3 6 Structure of the 8-bit code 3 6.1 Elements of the 8-bit code 3 6.2 Identification of the elements of the 8-bit code 4 6.3 Invocation 4 6.3.1 C0 set
13、5 4 6.3.2 Character SPACE 4 6.3.3 G0 set 4 6.3.4 Character DELETE 4 6.3.5 C1 set 5 4 6.3.6 G1 set 4 6.3.7 G2 set 4 6.3.8 G3 set 4 7 Specification of the characters of the 8-bit code 4 7.1 C0 set 4 7.2 Character ESCAPE 4 7.3 Character SPACE 4 7.4 G0 set 4 7.5 Character DELETE 6 7.6 C1 set 6ISO/IEC 48
14、73:1991(E) BSI 01-2000 iii Page 7.7 G1 set 7 7.8 G2 set 7 7.9 G3 set 7 7.10 Summary of the specification of the 8-bit code 7 8 Levels 7 8.1 Level 1 7 8.2 Level 2 7 8.3 Level 3 8 9 Version of the 8-bit code 8 9.1 Contents of a version 8 9.2 Unique coding of characters 8 10 Identification of version a
15、nd level 8 10.1 Purpose and context of identification 8 10.2 Identification of level 8 10.3 Identification of a version 8 10.4 Switching from one version to another 9 10.5 Switching from one level to another 9 Annex A (normative) Restrictions applicable to the C0 and C1 sets 13 Annex B (informative)
16、 Shift functions 13 Annex C (informative) Composite graphic characters 13 Annex D (informative) Use of bit combinations 00/14 and 00/15 14 Annex E (informative) Main differences between the 2nd edition (1986) and the present (third) edition of this International Standard 14 Figure 1 Elements of the8
17、-bit code 10 Figure 2 Level 1 11 Figure 3 Level 2 11 Figure 4 Level 3 12 Table 1 ESCAPE 4 Table 2 SPACE 4 Table 3 Graphic characters of the G0 set 5 Table 4 DELETE 6ISO/IEC 4873:1991(E) iv BSI 01-2000 Foreword ISO (the International Organization for Standardization) and IEC (the International Electr
18、otechnical 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 technic
19、al 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
20、 committee, ISO/IECJTC1. 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 least75% of the national bodies casting a vote. International Standard ISO/IEC4873 was prepar
21、ed by Joint Technical Committee ISO/IECJTC1, Information technology. This third edition cancels and replaces the second edition (ISO4873:1986), which has been technically revised. Annex A forms an integral part of this International Standard. Annex B, Annex C, Annex D and Annex E are for information
22、 only.ISO/IEC 4873:1991(E) BSI 01-2000 1 1 Scope This International Standard specifies an8-bit code derived from, and compatible with, the7-bit coded character set specified in ISO/IEC646. The characteristics of this code are also in conformance with the code extension techniques specified in ISO202
23、2. This International Standard specifies an8-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 an8-bit environment among data processing systems and assoc
24、iated 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 10digits as well as the52 small and capital letters of the basic Latin alphabet and may include accented letters, s
25、pecial 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
26、 this International Standard if all the coded representations of characters within that CC-data-element conform to the requirements of clause9. 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 co
27、nforms to the requirements of2.1.2.1, and either or both of2.1.2.2 and2.1.2.3. A claim of conformance shall identify the document which contains the description specified in2.1.2.1, and shall identify the version adopted. 2.1.2.1 Device description A device that conforms to this International Standa
28、rd 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 in2.1.2.2 and2.1.2.3. 2.1.2.2 Originating devices An originating device shall allow its user
29、to supply 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 withi
30、n a CC-data-element, and that conform to2.1.1, 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 code requires definitio
31、ns 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
32、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 Normati
33、ve 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 Internat
34、ional 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 InternationalStandards. ISO/IEC 646:1991, Information technology ISO 7-bit coded character set for information
35、 interchange. ISO 2022:1986, Information processing ISO 7-bit and 8-bit coded character sets Code extension techniques. ISO/IEC 6429:, Information technology Control functions for 7-bit and8-bit coded character sets 1) . 1) To be published.ISO/IEC 4873:1991(E) 2 BSI 01-2000 ISO/IEC 10367:1991, Infor
36、mation technology Standardized coded graphic character sets for use in8-bit codes. ISO International Register of Coded Character Sets to be Used with Escape Sequences (ISO2375). 4 Definitions For the purpose of this International Standard the following definitions apply. 4.1 active position the char
37、acter 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 NOTEIn general, the active position is indicated in a display by a cursor. 4.2 bit combination an ordered set of bits used for the representati
38、on 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 4.5 character position the portion of a display that is imaging or is capable of imaging a graphic symbol 4.6 coded-characte
39、r-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 or more identified standards for coded character sets NOTE 1In a communication environment according to the Reference Mode
40、l for Open Systems Interconnection (ISO7498), 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. NOTE 2When information interchange is accomplished by means of interchangeable media, a CC-d
41、ata-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 coded character set; code a set of unambiguous rules that establishes a character set and the one-to-one relationship between the characters of the
42、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 code table a table showing the character allocated to each bit combination in a code 4.10 control character a control function the coded repr
43、esentation of which consists of a single bit combination 4.11 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 4.12 device a component of information processing e
44、quipment which can transmit, and/or receive, coded information within CC-data-elements NOTEIt 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
45、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 no
46、rmally handwritten, printed or displayed, and that has a coded representation consisting of one or more bit combinationsISO/IEC 4873:1991(E) BSI 01-2000 3 4.16 graphic symbol a visual representation of a graphic character or of a control function 4.17 repertoire a specified set of characters that ar
47、e represented by means of one or more bit combinations of a coded character set 4.18 user a person or other entity that invokes the services provided by a device NOTE 1This entity may be a process such as an application program if the “device” is a code convertor or a gateway function, for example.
48、NOTE 2The 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 bit combinations of the8-bit c
49、ode are identified by b 8 , b 7 , b 6 , b 5 , b 4 , b 3 , b 2and b 1 , where b 8is the highest-order, or most-significant bit, and b 1is the lowest-order, or least-significant, bit. The bit combinations may be interpreted to represent integers in the range0 to255 in binary notation by attributing the following weights to the individual bits: In this International Standard, the bit combinations are identified by notations of the form xx/yy, where xx and yy are numbers in the range00 to15. The correspondence between the notations of the formxx
