ISO/IEC 9293:1994
(Main)Information technology — Volume and file structure of disk cartridges for information interchange
Information technology — Volume and file structure of disk cartridges for information interchange
Cancels and replaces the first edition (1987). Specifies the volume and file structure of disk cartridges for the interchange of information between users of information processing systems. Also specifies an optional record structure. Applicable to various types of disk cartidges. Specifies the location of files of information on an FDC and a set of recorded descriptors. Specifies requirements for the processes which are provided within information processing systems to enable information to be interchanged between different system, utilizing recorded FDSc as the medium of interchange. Provides a method for the allocation of space that is independent of the number of files which are recorded on the volume. Does not specify the content and the organization of the files.
Technologies de l'information — Volume et structure des fichiers des cartouches à disquette pour l'échange d'information
General Information
Relations
Standards Content (Sample)
INTERNATIONAL
ISO/IEC
STANDARD 9293
Second edition
1994-1 l-l 5
Information technology - Volume and file
structure of disk cartridges for information
interchange
Technologies de I’information - Volume et structure des fichiers des
cartouches a disquette pour I’khange d’information
Reference number
ISO/1 EC 9293: 1994(E)
ISO/IEC 9293: 1994 (E)
Page
Contents
Section 1 - Genera1
1 Scope
2 Conformance
2.1 Conformance of an FDC
2.2 Conformance of an information processing System
3 Normative references
4 Definitions
4.1 byte
4.2 data field of a sector
4.3 data interchange Standard
4.4 defective sector
4.5 descriptor
4.6 FDC
4.7 file
4.8 formatting
4.9 implementation
4.10 initiahzation
4.11 ODC
4.12 originating System
4.13 receiving System
4.14 sector
4.15 physical track
4.16 user
4.17 fixed-length record
4.18 record
4.19 Segment
4.20 segmented record
4.21 variable-length record
0 ISO/IEC 1994
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ISO/IEC 9293: 1994 (E)
0 ISO/IEC
5 Notations
5.1 Decimal and hexadecimal notations
5.2 Other notations
5.3 Capital letters
Section 2 - Requirements for the medium
6 Volume structure
6.1 Arrangement of data on an FD@
6.1.1 FDC Parameters
6.1.2 Physical Addresses
6.1.3 Logical Seetor Number
6.1.4 System Area and Data Area
6.1.5 Parameters of the Volume Structure
6.2 Arrangement of the Data Area
6.2.1 Clusters
6.2.2 Status of clusters
6.3 Arrangement of the System Area
6.3.1 FDC Descriptor and space for System use
6.3.2 File Allocation Table (FAT)
6.3.3 Root Directory
6.3.4 Size of the System Area
6.4 Files
6.4.1 File Spate
6.4.2 Relation to clusters
6.4.3 File length
6.5 Sub-directories
7 Content of a file
8 Recording of descriptor fields
8.1 Numerital values in one-byte fields
8.2 Numerital values in two-byte fields
8.3 Numerital values in four-byte fields
8.4 Pairs of 12-bit integers
8.5 Character set and coding
8.6 Justification of characters
9 FDC Descriptor
9.1 FDC Descriptor and Extended FDC Descriptor layout
9.2 FDC Descriptor and Extended FDC Descriptor Felds
9.2.1 Field reserved for System use (BP 1 to 3)
9.2.2 Creating System Identifier (BP 4 to 11)
9.2.3 Seetor Size (BP 12 and 13)
9.2.4 Seetors per Cluster (BP 14)
9.2.5 Reserved Seetor Count (BP 15 and 16)
. . .
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ISO/IEC 9293: 1994 (E)
9.2.6 Number of FATs (BP-17)
9.2.7 Root Directory Entries (BP 18 and 19)
9.2.8 Total Seetors (BP 20 and 21)
9.2.9 Medium Identifier (BP 22)
9.2.10 Seetors per FAT (BP 23 and 24)
9.2.11 Seetors per Track (BP 25 and 26)
9.2.12 Number of Sides (BP 27 and 28)
9.2.13 Field reserved for future standardization (FDC Descriptor BP 29 and 30)
9.2.14 Field reserved for System use (Extended FDC Descriptor BP 29 to 32)
9.2.15 Total Seetors (Extended FDC Descriptor; BP 33 to 36)
9.2.16 Field reserved for System use (Extended FDC Descriptor BP 37)
9.2.17 Field reserved for future standardization (Extended FDC Descriptor BP 38)
9.2.18 Extended Boot Record Signature (Extended FDC Descriptor BP 39)
9.2.19 Volume ID Number (Extended FDC Descriptor BP 40 to 43)
9.2.20 Volume Label (Extended FDC Descriptor BP 44 to 54)
9.2.21 File System Type (Extended FDC Descriptor BP 55 to 62)
9.2.22 Field reserved for System use (FDC Descriptor BP 31 to 5 12; Extended FDC Descriptor BP 63 to 5 12) 13
10 File Allocation Table
10.1 Format Identifier
10.2 FAT entries
10.2.1 FAT entry size
10.2.2 Number of FAT entries
10.2.3 FAT entry values
10.2.4 Maximum Cluster Number (W@
10.3 Number of sectors in each FAT
10.4 Recorded form of the FAT
11 File directories
11.1 Characteristics
11.2 Directory entry types
11.3 General definition of Directory Entry fields
Name (BP 1 to 8)
11.3.1
11.3.2 Name Extension (BP 9 to 11)
11.3.3 Attributes (BP 12)
Reserved Field (BP 13 to 22)
11.3.4
11.3.5 Time Recorded (BP 23 and 24)
11.3.6 Date Recorded (BP 25 and 26)
11.3.7 Starting Cluster Number (BP 27 and 28)
11.3.8 File Length (BP 29 to 32)
11.4 File Entry
11.4.1 Name (BP 1 to 8)
11.4.2 Name Extension (BP 9 to 11)
11.4.3 Attributes (BP 12)
11.4.4 Reserved Field (BP 13 to 22)
Time Recorded (BP 23 and 24)
11.4.5
11.4.6 Date Recorded (BP 25 and 26)
11.4.7 Starting Cluster Number (BP 27 and 28)
File Length (BP 29 to 32)
11.4.8
11.5 Volume Label Entry
0 ISO/IEC ISO/IEC 9293: 1994 (E)
11.5.1 Name and Name Extension (BP 1 to 11)
11.5.2 Attributes (BP 12) 18
11.5.3 Reserved Field (BP 13 to 22) 18
11.5.4 Time Recorded (BP 23 and 24) 18
11.5.5 Date Recorded (BP 25 and 26)
11.5.6 Starting Cluster Number (BP 27 and 28) 18
11.5.7 File Length (BP 29 to 32) 18
11.6 Sub-directory Pointer Entry 18
11.6.1 Name (BP 1 to 8) 19
Name Extension (BP 9 to 11)
11.6.2 19
11.6.3 Attributes (BP 12) 19
11.6.4 Reserved Field (BP 13 to 22) 19
11.6.5 Time Recorded (BP 23 and 24)
11.6.6 Date Recorded (BP 25 and 26) 19
11.6.7 Starting Cluster Number (BP 27 and 28) 19
11.6.8 File Length (BP 29 to 32) 19
11.7 Sub-directory Identifier Entry 19
11.7.1 Name (BP 1 to 8)
Name Extension (BP 9 to 11)
11.7.2 19
11.7.3 Attributes (BP 12) 19
11.7.4 Reserved Field (BP 13 to 22) 19
11.7.5 Time Recorded (BP 23 and 24)
Date Recorded (BP 25 and 26)
11.7.6 20
11.7.7 Starting Cluster Number (BP 27 and 28) 20
11.7.8 File Length (BP 29 to 32) 20
11.8 Sub-directory Parent Pointer Entry 20
11.8.1 Name (BP 1 to 8) 20
11.8.2 Name Extension (BP 9 to 11)
11.8.3 Attributes (BP 12) 20
11.8.4 Reserved Field (BP 13 to 22) 20
11.8.5 Time Recorded (BP 23 and 24) 20
11.8.6 Date Recorded (BP 25 and 26)
11.8.7 Starting Cluster Number (BP 27 and 28) 20
11.8.8 File Length (BP 29 to 32) 21
11.9 Not-currently-used Entry 21
11.9.1 Name Field (BP 1 to 8) 21
11.9.2 Remaining bytes (BP 9 to 32) 21
11.10 Never-used Entry 21
11.10.1 Name Field (BP 1 to 8)
11.10.2 Remaining bytes (BP 9 to 32)
Section 3 - Requirements for Systems 22
12 Requirements for the description of Systems 22
13 Requirements for an originating System 22
13.1 General
13.2 Files 22
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ISO/IEC 9293: 1994 (E)
13.3 Descriptors
14 Requirements for a receiving System
14.1 General
14.2 Files
14.3 Descriptors
Section 4 - Record structure
15 Record structure
15.1 General
15.2 Records
15.2.1 Characteristics
15.2.2 Measured Data Units
15.2.3 Fixed-length records
15.2.4 Variable-length records
15.2.5 Segmented records
15.3 Attributes of record-structured files
15.4 Requirements for Systems implementing section 4
15.4.1 Originating Systems
15.4.2 Receiving Systems
Annexes
A - Parameter values for other FDC formats
B - Parameter values for FDCs conforming to an International Standard for data interchange
C - ISO 646: International Reference Version (IRV)
D - Example of volume structure and file location
E - Index of acronyms
F - Extension to Partial ROM
ISO/IEC 9293: 1994 (E)
Foreword
ISO (the International Organization for Standardization) and IEC (the Inter-
national 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 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-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. Publication
as an International Standard requires approval by at least 75 % of the national
bodies casting a vote.
The first edition of International Standard ISO/IEC 9293 was prepared by the
ECMA (as Standard ECMA-107) and was adopted, under a special “fast-track
by Joint Technical Committee ISO/IEC JTC 1, Information
procedure”,
technology, in parallel with its approval by national bodies of ISO and IEC.
This second edition cancels and replaces the first edition (ISO 9293:1987); it
incorporates the capabilities of new disk cartridges (both Optical and magnetic).
Annex A forms an integral part of this International Standard. Annexes B to F are
for information only.
vii
ISO/IEC 9293: 1994 (E) 0 ISO/IEC
Introduction
For many purposes ISO 7665 provides a satisfactory data interchange between different of information-processing
tYPes
Systems. However, it imposes some restrictions on the Operation of a System as follows:
Esch individual file must be recorded on the disk in a sequential, “batch-processing” mode. After a set of files has been
a)
recorded on the disk, a file cannot be extended beyond its pre-determined length.
It is common practice in small Systems for the user to interact continuously with the System to update files. Files having
a suitable structure for this purposes are not within the Provision of ISO 7665.
The interchange cartridge has to be created by an “export” copy process from the application’s files, after the application
has terminated. A similar “import” process is required in the receiving System.
Limitations on the number of file labels permitted on an interchange disk cartridge prevent the full use of the disk space
W
if the average size of files is significantly less than, say 20 kbytes. For conventional data processing purposes such an
average file size is usually satisfactory. However, the file sizes typically encountered in text processing and small
Single-User Systems are very much smaller and would lead to very inefficient use of the disk space.
In view of these requirements it was decided to develop a second Standard for volume and file struchtre of disk cartridges, the
provisions of which were to be based on already existing practice in general use world-wide. Hence this International Standard
has the following beneficial characteristics, in addition to those of ISO 7665:
Direct updating of the interchange file by an interactive application is possible;
a>
There will be no limit on the number of individual files on a disk, within the Overall limitation of available space for
b)
holding files. Any file tan be extended whenever required.
The characteristics are advantageous for:
Interchange of sets of text files or of small files, or of multiple-part document files;
a>
Interchange of any file when sender and recipient wish to carry out frequent update of the file between interchange
b)
cycles, for example files of commercial transactions.
Since the publication of the first version of this International Standard, many types of high capacity Flexible Disk Cartridges
(FDCs) and Optical Disk Cartridges (ODCs) have come in use. All the descriptions (except annex B) of an FDC, throughout
this International Standard, tan be applied to an ODC as well. It is intended that existing file Systems for FDCs, possibly
slightly modified, are applicable to ODCs. ODC specific volume and file structure Standards are, e.g., ISO/IEC 13346 and
ISO/IEC 13490. This International Standard is applicable to the new types of storage media because of revision at the
following Points:
Addition of the extended FDC Descriptors (clause 9) to the existing FDC Descriptors;
a)
Adoption of 1 o-bit File Allocation Table (FAT) entries (10.2) in addition to the existing 12-bit FAT entries;
b)
Obsoletion of the Medium Identifier field (table 3 and subclause 9.2.9) because available values are exhausted and the
C>
field is no more used.
. . .
Vlll
INTERNATIONAL STANDARD @ ISo/IEC ISO/IEC 9293:1994 (E)
Information technology - Volume and file structure of disk cartridges for information
interchange
Section 1 - General
1 Scope
This International Standard specifies the volume and file structure of disk cartridges for the interchange of information
between users of information processing Systems. It also specifies an optional record structure.
Note - All the descriptions (except those in annex B) of Flexible Disk Cartridges (FDC) tan be applied to Optical Disk Cartridges (ODC) as well.
This International Standard is applicable to various types of disk cartridges including those identified in clause 3, and other
types which may be the subject of future International Standards.
This International Standard specifies the location of files of information on an FDC and also specifies a set of recorded
descriptors which identifies:
-
the files which may be interchanged;
-
the locations of the files;
-
the attributes of the files;
-
the location of unused space for recording on the FD@;
-
the location of defective recording space on the FDC;
-
the attributes of the FDC and of the descriptors recorded on it.
This International Standard also specifies requirements for the processes which are provided within information processing
Systems to enable information to be interchanged between different Systems, utilizing recorded FDCs as the medium of
interchange. For this purpose it specifies the functions within Systems which are intended to originate or to receive FDCs
which conform to this International Standard.
This International Standard provides a method for the allocation of space that Ps independent of the number of files which are
recorded on the volume. It also enables the sizes of the recorded files to be expanded or contracted during processing, subject
only to the availability of unused recording space when needed.
The content and organization of the files are not specified by this International Standard and are subject to agreement between
the originator and the recipient of the interchanged FDC.
Conformance
Conformance of an FDC
2.1
An FDC shall be in conformance with this International Standard when all information recorded on it conforms to the
requirements of section two of this International Standard.
A prerequisite to such conformance is the conformance of the FDC to the appropriate International Standard for data
interchange by means of FDCs.
2.2 Conformance of an information processing System
An information processing System shall be in conformance with this International Standard if it meets the set of requirements
specified in section three of this International 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 is met by the System.
Conformance with this International Standard does not require conformance with section 4.
ISO/IEC 9293: 1994 (E) 0 ISO/IEC
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 edition indicated was valid. All Standards are subject to revision, and Parties to
agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent
edition of the Standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO/IEC 646: 1991, Information technology - ISO 7-bit coded Character setfor information interchange.
ISO 7487-1:1993, - Data interchange on 130 mm (5,25 in) flexible disk cartridges using
Information technology
modified frequency modulation recording at 7 958 ftprad, I,9 tpmm (48 tpi), on both sides
Part 1: Dimensional, physical and magnetic chaacteristics.
Data interchange on 130 mm (525 in> flexible disk cartridges using
ISO 7487-3: 1986, Information processing -
modified frequency modulation recording at 7 958 ftprad, 1,9 tpmm (48 tpi), on 60th sides
Part 3: Track formst B.
ISO 7665:1983, Information processing - File structure and labelling of flexible disk cartridges for information
interchange.
ISO 8378-1: 1986, Information processing - Data interchange on 130 mm (5,25 in) flexible disk cartridges using
modified frequency modulation recording at 7 958fiprad, 3,8 tpmm (96 tpi), on both sides
-
Part 1: Dimensional, physical and magnetic characteristics.
Data interchange on 130 mm (5,25 in} flexible disk cartridges using
ISO 8378-3: 1986, Information processing -
modified frequency modulation recording at 7 958 ftprad, 3,8 tpmm (96 tpi), on both sides
-
Part 3: Track formst B.
ISO 8630-1:1987, Information processing - Data interchange on 130 mm (5,25 in) flexible disk cartridges using
modified frequency modulation recording at 13 262ftprad, on 80 tracks on each side
-
Part 1: Dimensional, physical and magnetic characteristics.
ISO 8630-3: 1987, Information processing - Data interchange on 130 mm (5,25 in) flexible disk cartridges using
modified frequency modulation recording at 13 262 ftprad, on 80 tracks on each side
-
Part 3: Track formst B for 80 tracks.
ISO 8860-1:1987, - Data interchange on 90 mm (3,5 in) flexible disk cartridges using
Information processing
modified frequency modulation recording at 7 958fiprad, on 80 tracks on each side
-
Part 1: Dimensional, physical and magnetic characteristics.
- Data interchange on 90 mm (3,5 in) flexible disk cartridges using
ISO 8860-2: 1987, Information processing
modijied frequency modulation recording at 7 958 ftprad, on 80 tracks on each side
-
Part 2: Track formst.
ISO/IEC 9171-1:1990, Information technology - 130 mm Optical disk cartridge, write once, for information interchange
-
Part 1: Unrecorded Optical disk cartridge.
ISO/IEC 9171-2:1990, Information technology - 130 mm Optical disk cartridge, write once, for information interchange
-
Part 2: Recording format.
- Data interchange on 90 mm (3,5 in) flexible disk cartridges
ISOfIEC 9529- 1: 1989, Information processing Systems
using modified frequency modulation recording at 15 916ftprad, on 80 tracks on each side
-
Part 1: Dimensional, physical and magnetic characteristics.
ISO/IEC 9529-2: 1989, Information processing Systems - Data interchange on 90 mm (3,5 in) flexible disk cartridges
using modified frequency modulation recording at 15 916 ftprad, on 80 tracks on each side
-
Part 2: Track formst.
Information technology - 130 mm rewritable Optical disk cartridge for information interchange.
ISO/IEC 10089:1991,
90 mm Optical disk cartridges, rewritable and read only, for data
ISOIIEC 10090: 1992, Information technology -
interchange.
ISO/IEC 10994: 1992, Information technology - Data interchange on 90 mm flexible disk cartridges using modified
frequency recording at 31 831 ftprad on 80 tracks on each side - ISO type 303.
0 ISO/IEC
ISOAEC 9293: 1994 (E)
ISOIIEC 11560: 1992, Information technology - Information interchange on 130 mm Optical disk cartridges using the
magneto-Optical effect, for write once, read multiple functionality.
ISO/IEC 13422:- ‘), Information technology - Data Interchange on 90 mm flexible disk cartridges 10 Mbytes capacity
using sector servo tracking - ISO type 304.
ISO/IEC 13481:1993, Information technology - Data interchange on 130 mm Optical disk cartridges - Capacity: 1
gigabyte per cartridge.
ISO/IEC 13549:1993, - Data interchange on 130 mm Optical disk cartridges - Capacity: 1,3
Information technology
gigabytes per cartridge.
ISO/IEC 13842:- ‘1, Information technology - 130 mm Optical disk cartridges - Capacity: 2 Gbytes per cartridge - For
information interchange.
ISO/IEC 13963:1994, Information technology - Data interchange on 90 mm Optical disk cartridges - Capacity: 230
megabytes per cartridge.
4 Definitions
For the purposes of this International Standard the following definitions apply.
4.1 byte : A string of binary digits operated upon as a unit. In this International Standard this term designates an g-bit
byte.
4.2 data field of a sector : A fixed-length field containing the data of a sector.
4.3 data interchange Standard : A Standard which defines the physical and magnetic characteristics, the recording
method, and the track format of an FDC.
4.4 defective sector : A sector which cannot be read or written without error.
4.5 descriptor : A recorded structure containing descriptive information about the volume or a file.
4.6 FDC : Flexible Disk Cartridge.
Note - All the descriptions of an FDC (except those in annex B) tan be applied to an Optical Disk Cartridge as well.
4.7 file : A named collection of information.
4.8 formatting : Writing the control information establishing the physical addresses of sectors on the surfaces of an FDC.
4.9 implementation : A set of processes which enable an information processing System to behave as an originating
System, or as a receiving System, or as both types of System.
4.10 initialization : Writing descriptors initiaally required to be on the FDC, Prior to the commencement of general
processing or use.
4.11 ODC : Optical Disk Cartridge
4.12 originating System : An information processing System which tan record files on an FDC for the purpose of data
interchange with another System.
4.13 receiving System : An information processing System which tan read files from an FDC which has been recorded by
another System for the purpose of data interchange.
4.14 sector : That part of a track on an FIX that tan be accessed independently of other parts of the track by the heads of
the FDC.
4.15 physical track : That part of an FDC that tan be accessed by a Single head that is stationary while the disk makes a
complete revolution.
4.16 user : A person or other entity (for example an application program) that Causes the invocation of the Services
provided by an implementation.
l) to be published
ISO/IEC 9293: 1994 (E) 0 ISO/IEC
In addition the following definitions apply specifically to section 4.
4.17 fixed-length record : A record contained in a file in which all records must have the same length.
4.18 record : Related data treated as a unit of information.
4.19 Segment : A part of a record.
segmented record : A record contained in a file in which the records may have different lengths and each record may
4.20
consist of one or more separate Segments.
4.21 variable-length record : A record contained in a file in which the records may have different lengths but a record
must not consist of separate Segments.
5 Notations
The following notations are used in this International Standard.
5.1 Decimal and hexadecimal notations
Numbers in decimal notation are represented by decimal digits, namely 0 to 9.
Numbers in hexadecimal notation are represented by hexadecimal digits, namely 0 to 9 and A to F, shown in parentheses.
5.2 Other notations
BP: Byte Position within a Descriptor, starting with 1
ZERO: A Single bit with the value 0
A Single bit with the value 1
ONE:
ip (x): The integer part of x
teil (x): The smallest integer that is not less than x
rem (x,y): The remainder of the integer division of x by y, that is, rem (x,y) = x - y x ip (dy)
5.3 Capital letters
Where a word or a group of words is used to designate a specific concept, for example the name of a descriptor field, it is
printed with initial capital letters except for prepositions.
0 ISO/IEC ISO/IEC 9293: 1994 (E)
Section 2 - Requirements for the medium
6 Volume structure
6.1 Arrangement of data on an FDC
6.1.1 FDC Parameters
For the purpose of this International Standard the significant Parameters of the data interchange Standard are shown in table 1.
Table 1 - FDC Parameters
FIX Parameter Acronym
NOS
Number of Recordable Sides
I
NOT
Number of Tracks per Side
1 Number of Seetors per Track SPT
Total Number of Seetors of the FDC TS
Number of Bytes per Data Field of a SS
Seetor
/
The values of these Parameters are given in data interchange Standards (See annex B).
6.1.2 Physical Addresses
Esch sector shall be identified by a Physical Address comprising the Side Number, the Track Number, and the Seetor Number.
The sides shall be numbered 0 and 1, tracks shall be numbered starting with 00, and the sectors shall be numbered starting with
1 on each track.
6.1.3 Logical Seetor Number
Esch sector on a volume shall be identified by a Logical Seetor Number. There shall be a one-to-one correspondence between
Physical Address and Logical Seetor Number. The Logical Seetor Numbers shall be assigned in an ascending sequence,
beginning with 0, starting at sector 1, track 00, side 0, continuing onto track 00, side 1 (if FDC is recordable on both sides) and
then to track 01, side 0, etc.
The relation between the Side Number (HN), Track Number (TN), Seetor Number (SN) and the Logical Seetor Number (UN)
shall be given by the formulae:
LSN=SPTx[HN+(NOSxTN)]+SN-I
SN =rem { rem [LSN, (SPT x NOS)], SPT) + 1
TN =“[SPzOS)
(rem[LSN , (SPT x NOS )])
HN =ip
SPT
6.1.4 System Area and Data Area
The space on an FDC shall be divided into a System Area and a Data Area.
The System Area shall occupy sectors with the Logical Seetor Numbers 0 to SSA-1, where SSA is the number of sectors in the
System Area (see 6.3.4). The System Area shall contain Descriptors which specify the recording format of the FDC describe
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ISO/IEC 9293: 1994 (E)
the use of the Data Area, and provide a Directory of the files on the volume. No part of any file shall be contained in the
System Area.
The Data Area shall occupy sectors with Logical Seetor Numbers starting with SSA. Interchange files and supplementary
Descriptors (such as Sub-directories) shall be contained in the Data Area. Files not intended for interchange may also be
contained in the Data Area.
6.1.5 Parameters of the Volume Structure
This International Standard specifies various types of data structure within the System Area and Data Area. The sizes of these
data structures are identified by a set of numerical Parameters. These Parameters are listed in table 2. See also annex B.
Table 2 - Parameters of the Volume Structure
Parameter Acronym
Seetors per Cluster SC
Reserved Seetor Count RSC
SF
1 Seetors per FAT
1 I
Root Directory Entries RDE
6.2 Arrangement of the Data Area
6.2.1 Clusters
The Data Area shall be organized into units of allocation called clusters. Esch cluster shall consist of the same number of
(See annex B). The data of a cluster shall be
sectors (Seetors per Cluster, XJ which shall be a power of 2, i.e. 1, 2, 4, 8, . . . .
recorded in the Data Fields of its constituent sectors.
If a cluster comprises more than one sector, the set of Logical Seetor Numbers (LSN) of its constituent sectors shall form a
consecutive ascending sequence.
Esch cluster shall be identified by a unique Cluster Number (UV). Cluster Numbers shall be integers, assigned in ascending
Order starting with 2. Cluster Number 2 shall be assigned to the cluster the first or only sector of which has the Logical Seetor
Number SSA. Esch successive Cluster Number shall be assigned to the cluster the sectors of which have the next higher set of
LSNs.
If the total number of sectors in the Data Area is not a multiple of SCthe remaining Seetors shall not be used.
The Logical Seetor Number of the first sector in a cluster shall be related to the Cluster Number by the following formula:
LSN = [(CN - 2) x SC] + SSA
where
LSN is the Logical Seetor Number;
CN is the Cluster Number;
SC is the number of sectors per cluster;
SSA is the size of the System Area in number of sectors (see 6.3.4).
6.2.2 Status of clusters
A Status shall be assigned to each cluster, and shall be one of the following:
-
allocated to a file;
-
available for allocation;
0 ISO/IEC ISO/IEC 9293: 1994 (E)
-
defective.
The Status of each cluster shall be identified in the File Allocation Table (FAT) in the System Area.
6.2.2.1 Clusters allocated to a file
The clusters allocated to contain a file shall be identified in the FAT. The clusters allocated to contain a file need not have
consecutive Cluster Numbers.
6.2.2.2 Clusters available for allocation
The clusters available for allocation shall be identified in the FAT. The clusters available for allocation need not have
consecutive Cluster Numbers.
The content of clusters available for allocation shall be ignored in interchange.
6.2.2.3 Defective Clusters
Clusters containing one or more defective sectors shall be marked as Defective Clusters in the FAT. The content of Defective
Clusters shall be ignored in interchange.
6.3 Arrangement of the System Area
The System Area shall contain an FDC Descriptor and space for System use, the Root Directory, and the File Allocation Table
(FAT) recorded twice.
6.3.1 FDC Descriptor and space for System use
The sector with Logical Seetor Number 0 shall contain the FDC Descriptor and space for System use.
The FDC Descriptor shall contain the FDC Parameters, an identifier of the System which recorded the FDC Descriptor and
information about the Parameters of the volume structure.
Additional sectors having successively higher Logical Seetor Numbers may also be reserved for System use. The content of
such sectors shall be ignored in interchange. The number sf sectors reserved for System use (RSC) shall include the sector the
LSN of which is 0. (See annex B).
6.3.2 File Allocation Table (FAT)
The FAT shall contain a Format Identifier and one entry for each cluster sf the Data Area of the FDC. These entries shall be
numbered consecutively starting with 2 and the Entry Number shall be equal to the Cluster Number of the corresponding
cluster.
Esch entry in the FAT shall indicate the Status of the corresponding cluster. The FAT entries shall be used to identify the set of
clusters that are allocated to each file. Annex D Shows an example of a FAT.
The number of sectors of the FAT (SF) shall be dependent on the number of clusters in the Data Area (See annex B).
The FAT shall be recorded in the System Area, in a sequence of sectors starting with the Logical Seetor Number equal to RSC.
The second occurrence of the FAT shall be recorded in a sequence of sectors immediately following the first occurrence of the
FAT.
6.3.3 Root Directory
The Root Directory shall be recorded in the System Area in a sequence of consecutive sectors immediately following the
second occurrence of the FAT. It shall contain a set of Root Directory Entries (RDE), each of which identifies a file, a Volume
Label or a sub-directory, or indicates that it is not in use (see annex B).
6.3.4 Size of the System Area
The size of the System Area (ssa>, in number of sectors, is given by the following formula:
SSA = RSC + 2SF + teil
0 ISO/IEC
ISOAEC 9293: 1994 (E)
where
RSC is the number of sectors preceding the first FAT, i.e. the Reserved Seetors Count;
SF is the number of sectors in the FAT;
RDE is the number of Root Directory Entries;
SS is the number of bytes in the Data Field of a sector.
6.4 Files
A file shall be an interchange file or a Sub-directory or a file not intended for interchange.
Esch file shall be identified by an entry in a Directory.
6.4.1 File Spate
Esch file shall be recorded in the Data Fields of the sectors of a set of clusters. This set shall be known as the File Spate of the
file. The Order of the clusters within the set shall be specified by their FAT entries.
The bytes in the File Spate shall be numbered consecutively. The numbering shall Start with 1, which shall be assigned to the
first byte of the first cluster of the File Spate. The numbering shall continue through successive bytes of the first cluster, and
then through successive bytes of each successive cluster (if any) of the File Spate. The numbering shall end with a number
equal to the number of bytes per cluster (i.e. SS &mult. Sc) multiplied by the number of clusters in the File Spate.
6.4.2 Relation to clusters
The Cluster Numbers of the clusters forming the File Spate of a file shall be recorded as a chain as follows:
- The Cluster Number of the first cluster of the File Spate shall be recorded in the Starting Cluster Number field of the
Directory entry of the file.
- For each cluster of the File Spate, except the last one, the corresponding FAT entry shall contain the Cluster Number of
the next cluster of the File Spate.
- For the last cluster of the File Spate, the corresponding FAT entry shall contain an entry indicating that it is the last cluster
of the file.
6.4.3 File length
The length of a file shall be the number of consecutive bytes in the File Spate, starting from the first byte, that are intended for
interchange. If this number is less than the number of bytes in the File Spate then any remaining bytes in the File Spate shall
be ignored in interchange.
6.5 Sub-directories
In addition to the Root Directory in the System Area, additional Directories called Sub-directories may be recorded as files in
the Data Area of the FDC Sub-directories shall contain Directory entries each of which identifies a file or another Sub-
directory, or indicates that it is not used.
The number of entries in a Sub-directory shall be calculated as follows:
-K xsc xss
iP
where K is the number of clusters allocated to the Sub-directory.
Esch Sub-directory shall be identified by one entry called a Sub-directory Pointer Entry in another directory.
The Directory containing this Sub-directory Pointer Entry shall be called the Parent Directory of the Sub-directory. Esch Sub-
directory shall have a Parent Pointer Entry which Points back to its Parent Directory. Different Sub-directories may have the
same Parent Directory.
A hierarchical relationship shall exist between the Root directory and all Sub-directories:
0 ISO/IEC
ISOAEC 9293: 1994 (E)
ROOT
SUB 1 SUB 2
SUB 3
The hierarchy shall consist of a number of levels (level 0, level 1, . . . ). The Root Directory shall be the one and only directory
at level0 of the hierarchy.
If a Parent Directory is at level y1 of the hierarchy, its Sub-directories shall be at level (n + 1). The number of levels of the
hierarchy is limited only by a restriction on the length of the virtual path name which shall be calculated as follows.
- The length of the virtual path name shall be the sum of
- the length of the file name;
-
if there is a file name extension, the length of the file name extension, plus 1;
the length of the names of all relevant Sub-directories;
- the length of the name extensions of all relevant Sub-directories;
-
the number of relevant Sub-directories;
-
the number of name extensions of all relevant Sub-directories.
This sum shall not exceed 63.
7 Content sf a file
The information in an interchange file shall be interpreted according to the relevant International Standards for the coded
representation of information.
Note - The identification of the Standard to which the coding of the information content of the file conforms is assumed to be the subject of an agreement
between originator and recipient of the file. This International Standard makes no general Provision for recording that identification on the FIX. However,
some selected Standards may be identified in the Name Extension Field of the File Entry of a Directory, see 11.51.
8 Recording of descriptor fields
8.1 Numerital values in one-byte Felds
A numerical value in a one-byte field shall be an 8-bit number recorded in binary notation.
8.2 Numerital values in two-byte Gelds
A numerical value in a two-byte field shall be a 16-bit number the hexadecimal representation (wx yz) of which shall be
recorded as (yz wx).
Note - For example, the decimal number 72 has (00 48) as its hexadecimal representation and is recorded as (48 00).
8.3 Numerital values in four-byte fields
A numerical value in a four-byte field shall be a 32-bit number the hexadecimal representation (st UV wx yz) of which shall be
recorded as (yz wx UV st).
Note - For example, the decimal number 305 419 896 has (12 34 56 78) as its hexadecimal representation and is recorded as (78 56 34 12).
8.4 Pairs of 12-bit integers
A pair of 12-bit numbers the hexadecimal representations of which are (abc) and (def) shall be recorded as (bc fa de). This
method shall be used for 12-bit FAT entries.
Note - For example, the pair of 12-bit numbers with hexadecimal representations (123) and (456) is recorded as (23 61 45).
8.5 Character set and coding
Unless otherwise stated, the characters in the Descriptors shall be coded according to ISO 646 (see annex C).
ISO/IEC 9293: 1994 (E) 0 ISO/IEC
The 37 characters in the following positions of the International Reference Version are referred to as d-characters:
310 to 319
411 to 5110
The 57 characters in the following positions of the International Reference Version are referred to as a-characters:
210 to 212
215 to 2115
310 to 3115
411 to 4115
510 to SI10
8.6 Justification of characters
In each field the content of which is specified by this International Standard to be d-characters, the d-characters shall be left-
justified and any remaining positions on the right shall be set to (20).
9 FDC Descriptor
The FDC Descriptor describes the formal of the disk and provides information about other Descriptors in the System Area of
the FDC.
This International Standard defines two types of FDC descriptors:
- FDC Descriptor
- Extended FDC Descriptor
The Extended FDC Descriptor is a superset of the FDC Descriptor. Only the Extended FDC Descriptor tan treat a volume with
more than 65 535 sectors, and it provides additional information to be used by the recipient System.
9.1 FDC Descriptor and Extended FDC Descriptor layout
Table 3a - FDC Descriptor
BP Acronym Content
Field Name
not specified
1 to 3 (reserved for System use)
4to 11 Creating System Identifier a-characters
,
12 and 13 Seetor size SS numerical value
SC
14 Seetors per cluster numerical value
Reserved sector count RSC numerical value
15 and 16
17 Number of FATs FN Number 2
RDE
18 and 19 Number of root-directory numerical value
entries
TS numerical value
20 and 21 Total sectors
not specified
22 Medium Identifier
or (F9)
1 SF numerical value
23 and 24 1 Seetors per FAT
1 25 and 26 1 Seetors per track 1 SPT I numerical value 1
1 NOS I numerical value 1
1 27 and28 I Number of sides
(Reserved for future
29 and 30
ww>
standardization)
(Reserved for System use) not specified
31 to 512
0 ISO/IEC
ISO/IEC 9293: 1994 (E)
Table 3b - Extended FDC Descriptor
BP Field Name Acronym Content
1 to 3 (reserved for System use) not specified
4to 11 Creating System Identifier a-characters
12 and 13 Seetor size SS numerical value
14 Seetors per cluster SC numerical value
15 and 16 Reserved sector count RSC numerical value
FN Number 2
17 Number of FATs
Number of root-directory RDE numerical value
18 and 19
entries
20and21 Total sectors TS numerical value
if < 65536
0 if > 65535
22 Medium Identifier not specified
OW or (W
SF
23 and 24 Seetors per FAT numerical value
Seetors per track SPT numerical value
25 and 26
27 and 28 Number of sides NOS numerical value
29 to 32 (Reserved for System use) not specified
TS numerical value
33 to 36 Total sectors
ifBP20&21 =0
Not specified
otherwise
not specified
37 (Reserved for System use)
38 Reserved
(00)
39 Extended Boot Record
(29)
Signature
40 to 43 Volume ID Number numerical value
44 to 54 Volume Label d-characters
55 to 62 File System Type d-characters
63 to 512 (Reserved for System use) not specified
9.2 FDC Descriptor and Extended FDC Descriptor Felds
9.2.1 Field reserved for System use (BP 1 to 3)
This field shall be reserved for System use. Its content is not specified by this International Standard and shall be ignored in
interchange.
9.2.2 Creating System Identifier (BP 4 to 11)
This field shall specify an identification for the System that has recorded the FDC Descriptor or the Extended FDC Descriptor.
The characters in this field shall be a-characters.
9.2.3 Seetor Size (BP 12 and 13)
This field shall specify the size of the Data Field of a sector.
It shall be recorded as a numerical value according to 8.2.
9.2.4 Seetors per Cluster (BP 14)
This field shall specify the number of sectors per cluster.
It shall be recorded as a numerical value according to 8.1.
ISO/IEC 9293: 1994 (E) 0 ISO/IEC
9.2.5 Reserved Seetor Count (BP 15 and 16)
This field shall specify the number of sectors reserved for System use.
It shall be recorded as a numerical value according to 8.2.
9.2.6 Number of FATs (BP 17)
This field shall specify the number 2.
It shall be recorded as a numerical value according to 8.1.
9.2.7 Rost Directory Entries (BP 18 and 19)
This field shall specify the number of entries in the Root Directory.
It shall be recorded as a numerical value according to 8.2.
9.2.8 Total Seetors (BP 20 and 21)
This field shall specify the number of sectors on the FDC (including defective sectors) if the total number of sectors is not
greater than 65 535. Otherwise, this field shall be recorded as ZEROS, and the total number of sectors shall be recorded in BP
33 to 36; in this case the Extended FDC Descriptor shall be used.
It shall be recorded as a numerical value according to 8.2.
9.2.9 Medium Identifier (BP 22)
The content of this field is not specified by this International Standard and shall be ignored in interchange.
Note - The reasons why this field is not specified are that the available values for this field are exhausted and the Geld is no more used.
9.2.10 Seetors per FAT (BP 23 and 24)
This field shall specify the number of sectors occupied by each occurrence of the FAT.
It shall be recorded as a numerical value according to 8.2.
9.2.11 Seetors per Track (BP 25 and 26)
This field shall specify the number of sectors in each track.
It shall be recorded as a numerical value according to 8.2.
9.2.12 Number of Sides (BP 27 and 28)
This field shall specify the number of recordable sides.
It shall be recorded as a numerical value according to 8.2.
9.2.13 Field reserved for future standardization (FDC Descriptor BP 29 and 30)
This field shall be reserved for future standardization.
It shall contain only ZEROS.
9.2.14 Field reserved for System use (Extended FDC Descriptor BP 29 to 32)
This field shall be reserved for System use.
Its content is not specified by this International Standard and shall be ignored in interchange.
9.2.15 Total Seetors (Extended FDC Descriptor; BP 33 to 36)
This field shall specify the number of sectors on the FDC (including defective sectors) if the field in BP 20 and 21 is recorded
as ZEROS.
It shall be recorded as a 32-bit numerical value according to 8.3.
0 ISO/IEC ISO/IEC 9293: 1994 (E)
9.2.16 Field reserved for System use (Extended FDC Descriptor BP 37)
This field shall be reserved for System use.
Its content is not specified by this International Standard and shall be ignored in interchange.
9.2.17 Field reserved for future standardization (Extended FDC
...
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