1、ANSI INCITS 27-1987 (R2003)(formerly ANSI X3.27-1987 (R1998)for information systems -file structure and labelingof magnetic tapesfor information interchangeANSI 03 X3.27-1987 Revision of ANSI X3.27-1978 American National Standard for Information Systems - File Structure and Labeling of Magnetic Tape
2、s for lnformation Interchange Secretariat Computer and Business Equipment Manufacturers Association Approved March 16, 1987 American National Standards Institute, Inc Abstract This standard specifies the volume and file structure for recording on magnetic tape and the requirements necessary to proce
3、ss those volumes and files. Four nested levels of the requirements on the media content are specified. The standard is primarily directed toward information interchange between implementations of potentially different architecture, but consideration is afforded to local tape processing needs. Such p
4、arochial requirements are recognized and considered, with the intent that the standard serve as a guide for designers of implementations that also support a local environment that is different from the interchange environment. Amer Natio ican Approval of an American National Standard requires verifi
5、cation by ANSI that the requirements for due process, consensus, and other criteria for rial approval have been met by the standards developer. Standard Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materi
6、ally affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely volu
7、ntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standards. The American National Standards lnstitute does not develop standards a
8、nd 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 American National Standard in the name of the American National Standards Institute. Requests for interpretations should be ad-
9、 dressed 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 time. The procedures of the American National Standards lnstitute require that action be taken periodically to reaffirm, re
10、vise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Published by American National Standards lnstitute 11 West 42nd Street, New York, New York 10036 Copyright 01 9
11、87 by American National Standards lnstitute All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States oi America Foreword (This Foreword is.not part o
12、f American National Standard X3.27-1987.) The aim of this standard is to reduce the difficulty of interchanging information recorded on magnetic tapes. This aim is accomplished by specifying the format, content, and arrangement of magnetically recorded labels to identify and describe the structure o
13、f files, and by specifying the format and arrangement of the blocks containing the records that constitute a file. This standard contains specifications for four levels of labeling. These levels are upward compatible so that an implementation conforming to a given level may read a volume set conform
14、ing to that or any lower levels. This standard is a revision of American National Standard Magnetic Tape Labels and File Structure for Information Interchange, ANSI X3.27-1978. The principal purpose of the revision is to have an American National Standard that is technically identical with Informati
15、on processing - File structure and labelling of magnetic tapes for information interchange, IS0 1001-1986. That revision of IS0 1001-1979 was accomplished by IS0 based on the work of the ECMA TC15 Committee on Labelling and File Structure. This edition of the standard differs technically from ANSI X
16、3.27-1978. The main differences are described in Appendix B. Suggestions for improvement of this standard are welcome. They should be sent to the Computer and Business Equipment Manufacturers Association, 311 First Street, NW, Washington, DC 20001. This standard was processed and approved for submit
17、tal to ANSI by American National Standards Committee on Information Processing Systems, X3. Committee approval of the standard does not necessarily imply that all members voted for its approval. At the time it approved this standard, the X3 Committee had the following members: Edward Lohse, Chair Ri
18、chard Gibson, Vice-Chair Catherine A. Kachurik, Administrative Secretary Organization Represented . American Express American Library Association American Nuclear Society AMP Incorporated . Association for Computing Machinery Association of the Institute for Certification of Computer Professionals .
19、 . AT - basic characteristics of the blocks containing the records constituting the file; - recorded labels for identifying files, file sections, and volumes of magnetic tapes; - four nested levels of interchange; - requirements for the processes which are provided within information processing syst
20、ems, to enable information to be interchanged between different systems, utilizing recorded magnetic tape as the medium of interchange; for this purpose it specifies the functions to be provided within systems which are intended to originate or receive magnetic tape volumes which conform to this sta
21、ndard. Conformance 2.1 Conformance of a Magnetic Tape Volume Set. A magnetic tape volume set conforms to this standard when all information recorded on it conforms to the specifications of this standard. A statement of conformance shall identify the lowest level of interchange to which the contents
22、of the magnetic tapes conform. A prerequisite to such conformance is conformance of each volume of the volume set to the same standard for recorded magnetic tape (see 4.18). 2.2 Conformance of an Information Processing System. An information processing system conforms to this standard if it meets al
23、l the requirements specified in this standard either for an originating system, or for a receiving system, or for both types of system. A statement of conformance shall identify which of these sets of requirements can be met by the system. 3. Referenced and Related Standards 3.1 Referenced Standards
24、 3.1.1 This standard is intended for use in conjunction with American National Standard for Infor- mation Systems - Coded Character Sets - 7-Bit American National Standard Code for Information Interchange (7-Bit ASCII), ANSI X3.4-1986. When this standard is superseded by a revision approved by the A
25、merican National Standards Institute, Inc, the revision shall apply. AIMERICAh NATIONAL STANDARD X3.27-1987 3.1.2 This standard is intended for use in conjunction with a standard for recorded magnetic tape (see 4.18). Such extant American National Standards include the following. When any of these s
26、tandards is superseded by a revision approved by the American National Standards Institute, Inc, the revision shall apply ANSI X3.14-1983, Information Systems - Recorded Magnetic Tape for Information Interchange (200 CPI, NRZI) ANSI X3.22-1983, Information Systems - Recorded Magnetic Tape for Inform
27、ation Interchange (800 CPI, NRZI) ANSI X3.39-1986, Information Systems - Recorded Magnetic Tape for Information Interchange (1600 CPI, Phase Encoded) ANSI X3.54-1986, Information Systems - Recorded Magnetic Tape for Information Interchange (6250 CPI, Group Coded Recording) NOTE: The standard for rec
28、orded magnetic tape used in conjunction with this standard is subject to agreement between the originator and the recipient of the volume. 32 Related Standards ANSI X3.40-1983, Information Systems - Unrecorded Magnetic Tape for Information Interchange (9-Track 800 CPI, NRZI; 1600 CPI, PE; and 6250 C
29、PI, GCR) ANSI X3.41-1974, Code Extension Techniques for Use with the 7-Bit Coded Character Set of American National Standard Code for Information Interchange 4. Definitions 4.1 Application Program. A program that processes the contents of records belonging to a file, and may also process selected at
30、tribute data relating to the file or to the volume(s) on which it is recorded. NOTE: An application program is a specific class of user as defined in this standard. 42 Block. A group of bytes recorded consecutively in accordance with the relevant standard for recorded magnetic tape. NOTE: The minimu
31、m and maximum lengths of a block are specified in the relevant standard for recorded magnetic tape. 4.3 Blocked. An attribute of records and record segments that indicates that they may begin at a byte that is not the first byte of a block. 4.4 Byte. A string of eight binary digits operated upon as
32、a unit. 4.5 File. A named collection of information consisting of zero or more records. 4.6 File Section. That part of a file that is recorded on any one volume. 4.7 File Set. A collection of one or more files recorded consecutively on a set of volumes. 4.8 Fixed-Length Record. A record contained in
33、 a file in which all records must have the same length. 4.9 Implementation. A set of processes within an information processing system which enable that system to behave as an originating system, or as a receiving system, or as both types of system. 4.10 Installation. A person or other entity which
34、controls the use of one or more implementations which process and interchange magnetic tapes. NlOTE: An installation is a specific class of user as defined in this standard. 4.11 Label. A record that identifies and characterizes a volume, or a file section on a volume. 4.12 Originating System. An in
35、formation processing system which can record a file set on a volume set for the purpose of data interchange with another system. 4.13 Originator. A person who is responsible for issuing commands to an originating system. AMERICAN NATIONAL STANDARD X3.27-1987 4.14 Receiving System. An iriformation pr
36、ocessing system which can read a file set from a volume set which has been recorded by another system for the purpose of data interchange. 4.15 Recipient. A person who is responsible for issuing commands to a receiving system. 4.16 Record. Related data treated as a unit of information. 4.17 Segmente
37、d Record. A record contained in a file which is assigned to contain records that may have different lengths and that may be recorded entirely in one block or over more than one block. 4.18 Standard for Recorded Magnetic Tape. A standard that specifies the recording method and the track format of a m
38、agnetic tape (for example, see 3.1.2). 4.19 Tape Mark. A control block used as a delimiter. NOTE: The structure of tape marks is specified by the relevant standards for recorded magnetic tape. 4.20 User. A person or other entity that causes the invocation of the services provided by an implementatio
39、n. 4.21 Variable-Length Record. A record contained in a file in which the records may have different lengths. 4.22 Volume. A dismountable reel of magnetic tape. 4.23 Volume Set. A collection of one or more volumes, on which a file set is recorded. 5. Notation The following notation is used in this s
40、tandard: BP Byte position within the label L Length of the field in number of byte positions Digit(s) Any digit from ZERO to NINE With the exception of SPACE, a group of capital letters in the content column of a table specifying label contents indicates that these characters shall appear in the ord
41、er given and in the corresponding byte positions of the field specified, for example, VOL in BP 1 to 3 of the Volume Header Labels. In the tables and throughout this standard, SPACE signifies the character coded in position 2/0 of ANSI X3.4-1986. 6. Arrangement of Labels and Files 6.1 Arrangement of
42、 Data on a Volume. A volume shall be recorded with a sequence of blocks and tape marks. The sequence shall commence with a block and shall terminate within the usable recording area. 6.2 Arrangement of Label Groups 6.2.1 Labels. A label shall be a record that shall have a length of 80 bytes. Each la
43、bel shall be recorded within the first or only 80 byte positions of a block. If the block contains any additional bytes, they shall be recorded with any desired bit combinations. Each label shall be one of the following types: Volume Header Installation Volume File Header User File Header End of Fil
44、e End of Volume User File Trailer AMERICAN NATIONAL STANDARD X3.27-1987 16.2.2 Label Sets. A sequence of one or more labels of the same type, recorded in consecutive blocks, shall be a label set of that type. All labels in a set shall be numbered consecutively starting from 1, except those labels in
45、 User File Header and User File Trailer Label Sets. The labels in User File Header and User File Trailer Label Sets may be identified in any order and may contain duplicate identifiers within a set. 16.2.3 Label Groups. A label group shall consist of a mandatory label set, optionally followed by a s
46、econd label set of a different type. Each label group shall be one of the types listed in the table below, anti shall include only those label sets listed in the corresponding entry of the table. The first set listed in each table entry is the mandatory set, and the second set listed is the optional
47、 set. Label Group Label Sets Beginning of Volume Volume Header Installation Volume Beginning of File Section End of File Section End of File File Header User File Header End of Volume User File Trailer End of File User File Trailer 6.3 Arrangement of File Sections 6.3.1 File Section. A file section
48、shall be recorded in a sequence of one or more blocks, or no blacks. If no blocks are recorded, the file section is regarded as empty. 16.3.2 Labeled-Sequence 6.3.2.1 A Labeled-Sequence shall consist of the sequence of blocks and tape marks as listed below, recorded consecutively: - Beginning of Fil
49、e Section Label Group - tape mark - a file section - , tape mark - either an End of File Label Group or an End of File Section Label Group, as required in 6.3.2.2 - tape mark 6.3.2.2 If the file section is the last or only file section of a file, then the label group that follows it shall be an End of File Label Group. Otherwise the label group shall be an End of File Section Label Group. NOTE: An Enc of File Section Label Group can only be the last label group on a volume because of the requirements of 6.5.1. 6.3.2.3 Within a Labeled-Sequence the information contained in the File Header L
