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1、kNSIINCITS 4-1986 (RI993 (formerly ANSI X3.4-1986 1997) ADOPTED FOR USE BY THE FEDERAL GOVERNMENT WA- b PUB 1-2 SEE NOTICE ON INSIDE for Information Systems - Coded Character Sets - 7-Bit American National Standard for In forma tion In terchange (7- Bit ASCII) Code Developed by Where IT all begins C
2、opyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 07/16/2007 00:40:38 MDTNo reproduction or networking permitted without license from IHS -,-,- This standard has been adopted for Federal Governm
3、ent use. Details concerning its use within the Federal Government are contained in Federal Information Processing Standards Publication 153, Programmers Hierarchical Interactive Graphics System (PHIGS). For a complete list of the publications available in the Federal Information Processing Standards
4、 Series, write to the Standards Processing Coordinator (ADP), National Institute of Standards and Tech- nology, Gaithersburg, MD 20899. Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 07/16/2
5、007 00:40:38 MDTNo reproduction or networking permitted without license from IHS -,-,- Approval of an American National Standard requires review by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is establishe
6、d when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be consid
7、ered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, proc
8、esses, or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an Ame
9、rican National Standard in the name of the American National Standards Institute. Requests for interpretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any t
10、ime. The procedures of the American National Standards Institute require that action be taken periodically to reaffirm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards
11、Institute. American National Published by American National Standards Institute 11 West 42nd Street, New York, New York 10036 Copyright O1 986 by Information Technology Industry Council (ITI) All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval s
12、ystem or otherwise, without prior written permission of ITI, 1250 Eye Street NW, Washington, DC 20005. Printed in the United States of America Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale,
13、07/16/2007 00:40:38 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI X3.4-1986 Revision of ANSI X3.4-1977 American National Standard for Information Systems - Coded Character Sets - 7- Bit American National Standard Code for Information Interchange (7- Bit ASCII) Secret
14、ariat Computer and Business Equipment Manufacturers Association Approved March 26, 1986 American National Standards Institute, I nc Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 07/16/2007
15、00:40:38 MDTNo reproduction or networking permitted without license from IHS -,-,- (This Foreword is not part of American Nitional Standard X3.4-1986.) Foreword This American National Standard presents the standard coded character set to be used for information interchange among information processi
16、ng systems, communication systems, and associated equipment. Other standards prescribe the means of implementing this standard in media, such as per- forated tape, punched cards, magnetic tape, magnetic tape cassette and cartridges, and optical character recognition. Further standards deal with erro
17、r control, data communi- cation formats, keyboards, graphic representation of control characters, code extension techniques, and media labels and file structures. The 7-bit coded character set was developed from a careful review of past work in the field and after a comprehensive program of original
18、 research and code design was com- pleted. Careful consideration has been given to the several conflicting requirements for code sets and their resolution is reflected in the standard code. This standard is a revision of American National Standard Code for Information Inter- change, ANSI X3.4-1977,
19、and was developed in parallel with its international counterpart, Informational Processing - IS0 7-Bit Coded Character Set for Information Interchange, IS0 646-1983. This current revision retains the same technical relationship to IS0 646- 1983 as the earlier edition. The text of this revision is qu
20、ite close to that of IS0 646- 1983. Changes were made to adopt more customary U.S. terminology and to reduce ambiguity. A conformance section has been added to aid users in building compatible equipment. The relationship with American National Standard Code Extension Tech- niques for Use with the 7-
21、Bit Coded Character Set of American National Standard Code for Information Interchange, ANSI X3.41-1974, has also been included. Suggestions for improvement of this standard will be welcome. They should be sent to the Computer and Business Equipment Manufacturers Association, 3 1 1 First Street, NW,
22、 Suite 500, Washington, DC 20001. This standard was processed and approved for submittal to ANSI by American Na- tional Standards Committee on Information Processing Systems, X3. Committee approval of the standard does not necessarily mean that all committee members voted for its approval. At the ti
23、me it approved this standard, the X3 Committee had the fol- lowing members: Edward Lohse, Chair Richard Gibson, Vice-Chair Catherine A. Kachurik, Administrative Secretary Organization Represented Name of Representative American Express. D. L. Seigal Lucille Durfee (Alt) American Library Association.
24、 . Paul Peters American Nuclear Society Geraldine C. Main D. R. Vondy (Alt) AMP Incorporated Patrick E. Lannan Edward Kelly (Alt) Association for Computing Machinery . Kenneth Mage1 Jon A. Meads (Alt) Association of the Institute for Certification of Computer Professionals. Thomas M. Kurihara AT tha
25、t is, no action shall be taken and there shall be no effect on the interpretation of subsequent characters. (3) Shall image all 94 graphic characters such that each character is recognizable as being associated with one of its names and such that each character is dis- tinguishable from the other gr
26、aphic characters. No other graphic character may be substituted for any of the graphic characters in the set. 2.2 Implementation. The use of this character set re- quires definitions of its implementation in various media. For example, these could include punched tapes, punched cards, magnetic media
27、, and transmis- sion channels, thus permitting interchange of data to take place either indirectly by means of an intermedi- ate recording in a physical medium, or by local con- nection of various units (such as input and output de- vices and computers) or by means of data transmission equipment. Th
28、e implementation of this coded charac- ter set in physical media and for transmission, taking into account the need for checking errors, is the sub- ject of other American National Standards and Inter- national Standards (see Appendix E). 3. Definitions 3.1 Active Position. The character position at
29、 which the action required by the next character in the data stream is to be effected. If the next character is a graphic character, it is imaged at that position, if it is a control character, the corresponding function is per- formed relative to that position. 3.2 Bit Combination. An ordered set o
30、f bits used for the representation of characters. 3.3 Character. A member of a set of elements used for the organization, control, or representation of data. 3.4 Character Position. A position on an imaging de- vice at which a graphic character can be imaged. 3.5 Coded Character Set; Code. A set of
31、unambigu- ous rules that establishes a character set and the one- to-one relationship between the characters of the set and their assigned bit combinations. 3.6 Code Extension. The techniques for encoding characters that are not included in the character set of a given code. 3.7 Code Table. A table
32、showing the character allo- cated to each bit combination in a code. 3.8 Control Character. A control function that is coded as a single bit combination. 3.9 Control Function. An action that affects the re- cording, processing, transmission, or interpretation of data and that has a coded representat
33、ion consisting of one or more bit combinations. 3.10 Graphic Character. A character, other than a con- trol function, that has a visual representation normally handwritten, printed, or displayed. Copyright American National Standards Institute Provided by IHS under license with ANSI Licensee=IHS Emp
34、loyees/1111111001, User=Wing, Bernie Not for Resale, 07/16/2007 00:40:38 MDTNo reproduction or networking permitted without license from IHS -,-,- AMERICAN NATIONAL STANDARD X3.4-1986 3.1 1 Graphic Symbol. A visual representation of a graphic character or of a control function. 3.12 Code Table Posit
35、ion. That part of a code table identified by its column and row coordinates. 3.13 Small Letter. A lowercase letter. 3.14 Capital Letter. An uppercase letter 4. Specification of the Coded Character Set The bits of the bit combinations of the 7-bit code are identified by b7. b6, b5, b4, b3, bz, and bl
36、 ,where b7 is the highest order bit (most significant bit), and bl is the lowest order bit (least significant bit). The bit combination may be interpreted to represent num- bers in the range O to 127 in binary notation by at- tributing the following weights to the individual bits: Bit: b7 b6 bS b4 b
37、3 bz bi Weight : 64 32 16 08 04 02 O1 In this standard, the bit combinations are identified by notation of the form x/y, where x is a number in the range O to 7 andy is a number in the range O to 15. The correspondence between the notations of the form x/y and the bit combinations consisting of the
38、bits b7 to bl is as follows: (i) x is the number represented by b7, b6, and b5, where these bits are given the weights 4,2, and 1, re- spect ively . (2) y is the number represented by b4, b3, b2, and bl ,where these bits are given the weights 8,4,2, and 1 , respectively. The notations of the form x/
39、y are the same as the ones used to identify positions in the code table where x is the column number and y the row number (see Section 6). The 128 bit combinations of the 7-bit code repre- sent control characters and graphic characters. The allocation of characters to bit combinations is based on th
40、e following principles: (1) The bit combinations 0/0 to 1/15 represent 32 control characters (2) The bit combination 2/0 represents the charac- ter SPACE, which is interpreted both as a control char- acter and as a graphic character (3) The bit combinations 2/1 to 7/14 represent 94 graphic character
41、s (4) The bit combination 7/15 represents the control character DELETE The allocation of individual characters to the bit combinations of the 7-bit code is specified in 4.1,4.2, and 4.3. This standard assigns at least one name to each char- acter. In addition, it specifies an acronym for each con- t
42、rol character and for the character SPACE, and a graphic symbol for each graphic character. By conven- tion, only capital letters and hyphens are used for writing the names of the characters, except when writ- ing the names of small letters. For acronyms. only capital letters and digits are used. It
43、 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. How- ever, this standard does not restrict the meanings of graphic characters. Neither does it specify a part
44、icular style or font design for the graphic characters when imaged. 4.1 Control Characters. The control characters of the 7-bit coded character set are classified in the following categories: (1 ) Transmission Control Characters. Transmission control characters are intended to control or facilitate
45、transmission of information over telecommunication networks. Procedures for the use of the transmission control characters on telecommunication networks are the subjects of other standards and correspond to Open Systems Interconnection (OSI) levels i through 4 (see ANSI X3.28-1976 and Appendix E). T
46、ransmis- sion control characters may also be referred to as communication control characters. (2) Fomat Effectors. Format effectors are mainly intended to control the layout and positioning of in- formation on character-imaging devices, such as print- ing and display devices. (3) Code Extension Cont
47、rol Characters. Code ex- tension control characters are used to extend the char- acter set of the code. They may alter the meaning of one or more bit combinations that follow them in the data stream. Procedures for the use of the code exten- sion control characters are specified in ANSI X3.41- 1974.
48、 (4) Device Control Characters. Device control characters are intended to control local or remote devices or ancillary devices connected to a data pro- cessing or data communication system. These control characters are not intended to control data communi- cation systems; this should be achieved by
49、the use of transmission control characters. are used to separate and qualify data logically. There are four such characters. They may be used in either hierarchical or nonhierarchical order; in the latter case, their !,pecific meanings depend on the application. (5) Information Separators. Information separators 8 Copyright American National Standards Institute Provided by IHS