6 Volume structure

6.1 Arrangement of data on a CD-ROM

6.1.1 Physical Addresses

Each sector shall be identified by a unique Physical Address as specified in the relevant ISO/IEC 10149.

6.1.2 Logical Sector

The sectors of a volume shall be organized into Logical Sectors. Each Logical Sector shall consist of a number of bytes equal to 2 048 or 2n, whichever is larger, where n is the largest integer such that 2n is less than, or equal to, the number of bytes in the Data Field of any sector recorded on the volume. The number of bytes in a Logical Sector shall be referred to as the Logical Sector Size. Each Logical Sector shall begin in a different sector from any other Logical Sector, and shall begin with the first byte of the Data Field of the sector in which it begins. If the number of bytes of the Data Field of each sector recorded on the volume is less than 2 048, a Logical Sector shall comprise more than one sector, and the set of the Physical Addresses of its constituent sectors shall form a consecutive ascending sequence. The data of a Logical Sector shall be recorded in the Data Fields of its constituent sectors.

Each Logical Sector shall be identified by a unique Logical Sector Number. Logical Sector Numbers shall be integers assigned in an ascending sequence, in order of ascending Physical Addresses of the constituent sectors, starting with O for the Logical Sector containing the sector having the lowest Physical Address which may contain recorded information. The numbering shall continue through successive Logical Sectors, each of which begins with the sector with the next higher Physical Address than that of the last sector constituting the previous Logical Sector.

6.1.3 Volume Space

The information on a volume shall be recorded in the set of all Logical Sectors on the volume. This set shall be referred to as the Volume Space of the volume.

The bytes in the Volume Space shall be numbered consecutively. The numbering shall start with 1, which shall be assigned to the first byte of the first Logical Sector of the Volume Space. The numbering shall continue through successive bytes of the first Logical Sector, and then through successive bytes of each successive Logical Sector, of the Volume Space.

6.2 Arrangement of the Volume Space

6.2.1 System Area and Data Area

The Volume Space shall be divided into a System Area and a Data Area.

The System Area shall occupy the Logical Sectors with Logical Sector Numbers O to 15. The System Area shall be reserved for system use. Its content is not specified by this International Standard.

The Data Area shall occupy the remaining Logical Sectors of the Volume Space.

6.2.2 Logical Block

The Volume Space shall be organized into Logical Blocks. Each Logical Block shall consist of 2n+9 bytes, where n equals O or a positive integer. The number of bytes in a Logical Block shall be referred to as the Logical Block Size which shall not be greater than the Logical Sector Size.

Each Logical Block shall be identified by a unique Logical Block Number. Logical Block Numbers shall be integers assigned in ascending order starting with O. Logical Block Number O shall be assigned to the Logical Block which begins with the first byte of the Volume Space. Each successive Logical Block Number shall be assigned to the Logical Block which begins with the byte in the Volume Space immediately following the last byte of the preceding Logical Block.

6.3 Arrangement of the Data Area

File Sections shall be recorded in the Data Area. More than one File Section of a file may be recorded on the same volume.

The following types of descriptors shall be recorded in the Data Area to describe the use of the Data Area:

• Volume Descriptors
• File Descriptors
• Directory Descriptors
• Path Tables

The Volume Descriptors shall be recorded in consecutively numbered Logical Sectors starting with the Logical Sector having Logical Sector Number 16. The Logical Sectors in the Data Area shall be available for the assignment of Volume Partitions and the recording of File Sections, File Descriptors, Directory Descriptors and Path Tables.

Each File Section shall be recorded in an Extent, and shall be identified by a descriptor in a directory. An Extended Attribute Record can be associated with the File Section. If present, it shall be recorded in the same Extent as the associated File Section, and shall be identified by the descriptor that identifies the associated File Section. Each directory shall be recorded as a file in a single Extent, and shall be identified by a Directory Descriptor either in another directory or in a Volume Descriptor. Each directory shall also be identified by a record in a Path Table. Each Path Table shall be identified in a Volume Descriptor.

Space within the Data Area may be assigned to one or more Volume Partitions. Each Volume Partition shall be recorded in an Extent and shall be identified by a Volume Descriptor.

6.4 Arrangement of Extents

6.4.1 Extent

An Extent shall be a set of Logical Blocks, the Logical Block Numbers of which form a continuous ascending sequence.

6.4.2 Mode of recording a File Section

A File Section, and its associated Extended Attribute Record if any, shall be recorded in an Extent either in interleaved mode or in non-interleaved mode.

6.4.3 Interleaved mode

6.4.3.1 File Unit

A File Unit shall comprise a set of Logical Blocks that are within an Extent and the Logical Block Numbers of which form a continuous ascending sequence.

When a File Section is recorded in interleaved mode, one or more File Units, each consisting of the same number of Logical Blocks, shall be assigned to the File Section within the same Extent. The number of Logical Blocks in the File Unit shall be the assigned File Unit Size for the File Section.

The first Logical Block of each File Unit shall have a Logical Block Number which is the lowest Logical Block Number in the Logical Sector that contains that Logical Block.

The sequence of the File Units in an Extent shall correspond to the sequence of the Logical Block Numbers of the first Logical Block of each File Unit.

NOTE - The Logical Blocks comprising a File Unit assigned to a File Section may

• also each be assigned to a different File Section, and/or
• comprise part of one or more Volume Partitions.

6.4.3.2 Interleave Gap

An Interleave Gap shall comprise the set of Logical Blocks that are within an Extent and the Logical Block Numbers of which lie between the last Logical Block Number of a File Unit and the first Logical Block Number of the next File Unit, if any, in the sequence. All Interleave Gaps between the File Units assigned to a File Section shall comprise the same number of Logical Blocks. This number shall be the assigned Interleave Gap Size for the File Section.

NOTE - The Logical Blocks comprising an Interleave Gap between the File Units assigned to a File Section may

• also each be assigned to a different File Section, and/or
• comprise part of one or more Volume Partitions.

6.4.3.3 Relation of File Section to File Unit

When a File Section is recorded in interleaved mode, the File Section, and its associated Extended Attribute Record, if any, shall be recorded over the sequence of File Units assigned to the File Section.

6.4.3.4 Recording of an Extended Attribute Record

If an Extended Attribute Record is recorded it shall be recorded in the first File Unit of the sequence. The recording shall begin at the first byte of the first Logical Block of the File Unit. It shall continue through successive bytes of that Logical Block, and then through successive bytes of successive Logical Blocks, if any, of the File Unit, until all of the Extended Attribute Record is recorded.

The assigned Extended Attribute Record length shall be equal to the assigned File Unit Size.

6.4.3.5 Recording of a File Section

The successive parts, if any, of the File Section shall be recorded in successive File Units, starting from the second File Unit in the sequence if an Extended Attribute Record is recorded, and starting from the first File Unit in the sequence if no Extended Attribute Record is recorded.

6.4.3.6 Data Space

The set of File Units in which the successive parts of the File Section are recorded shall be the Data Space of the File Section.

The bytes in the Data Space shall be numbered consecutively. The numbering shall start from 1 which shall be assigned to the first byte of the first Logical Block of the first File Unit, if any, of the Data Space. The numbering shall continue through successive bytes of that Logical Block, then through successive bytes of each successive Logical Block, if any, of the first File Unit, and then through successive bytes of the Logical Block(s) of each successive File Unit, if any, assigned to the File Section.

The numbering shall end with a number equal to the number of bytes in which the File Section is recorded in the Data Space; or this number shall equal zero if there are no bytes of the file recorded in the Data Space.

6.4.4 Non-interleaved mode

When a File Section is recorded in non-interleaved mode the File Section, and its associated Extended Attribute Record, if any, shall be recorded over the sequence of Logical Blocks in an Extent.

6.4.4.1 Recording of an Extended Attribute Record

If an Extended Attribute Record is recorded, it shall be recorded over one or more Logical Blocks, the Logical Block Numbers of which form a continuous ascending sequence. The recording shall begin at the first byte of the first Logical Block of the Extent. It shall continue through successive bytes of that Logical Block, and then through successive bytes of successive Logical Blocks, if any, of the Extent, until all of the Extended Attribute Record is recorded.

The number of Logical Blocks over which the Extended Attribute Record is recorded shall be the assigned Extended Attribute Record length for the File Section.

NOTE - The Logical Blocks comprising an Extended Attribute Record assigned to a File Section may

• also each be assigned to a different File Section, and/or
• comprise part of one or more Volume Partitions.

6.4.4.2 Recording of a File Section

The File Section shall be recorded over zero or more Logical Blocks, the Logical Block Numbers of which form a continuous ascending sequence. If no Extended Attribute Record is recorded, the sequence shall start with the first Logical Block of the Extent. If an Extended Attribute Record is recorded, the sequence shall start with the first Logical Block, if any, immediately following the last Logical Block over which the Extended Attribute Record is recorded.

6.4.4.3 Data Space

The set of Logical Blocks over which the File Section is recorded shall be the Data Space of the File Section.

The bytes in the Data Space shall be numbered consecutively. The numbering shall start from 1 which shall be assigned to the first byte of the first Logical Block, if any, of the Data Space. The numbering shall continue through successive bytes of that Logical Block, then through successive bytes of each successive Logical Block, if any, of the Data Space.

The numbering shall end with a number equal to the number of bytes in which the File Section is recorded in the Data Space; or this number shall equal zero if there are no bytes of the file recorded in the Data Space.

6.4.5 Data length of a File Section

The data length of a File Section shall be the number of bytes in which the File Section is recorded in the Data Space. If this number is less than the number of bytes in the Data Space, then any remaining bytes in the Data Space shall be ignored in interchange.

6.4.6 Relation of Extended Attribute Record to File Section

An Extended Attribute Record may be associated with a File Section. If present, the Extended Attribute Record shall identify certain attributes of the file of which the File Section forms a part.

A subset of those attributes shall apply to all File Sections of a file that contains records according to 6.10. If any of those attributes are assigned to the file, an Extended Attribute Record shall be recorded in association with each of the File Sections of the file.

The other attributes identified in an Extended Attribute Record shall apply to that File Section and all preceding File Sections of the file (see 6.5.1). If no Extended Attribute Record is recorded in association with the last File Section of a file, then these attributes are not specified for the file.

6.4.7 Recording of a Volume Partition

If a Volume Partition is recorded, it shall be recorded over one or more Logical Blocks, the Logical Block Numbers of which form a continuous ascending sequence. The recording shall begin at the first byte of the first Logical Block of the Extent. It shall continue through successive bytes of that Logical Block, and then through successive bytes of successive Logical Blocks, if any, of the Extent, until all of the Volume Partition is recorded. The first Logical Block of each Volume Partition shall have a Logical Block Number which is the lowest Logical Block Number in the Logical Sector that contains that Logical Block.

The number of Logical Blocks over which the Volume Partition is recorded shall be the assigned Volume Partition Size for the Volume Partition.

6.5 File structure

6.5.1 Relation to File Sections

Each file shall consist of one or more File Sections. Each File Section of a file shall be identified by a record in the same directory. The sequence of the File Sections of a file shall be identified by the order of the corresponding records in the directory.

A File Section may be part of more than one file and may occur more than once in the same file. A File Section may be identified by more than one record in the same or a different directory.

Each File Section of a file may be recorded on a different volume.

6.5.2 Numbering of bytes in a file

The bytes comprising a file shall be numbered consecutively. The numbering shall start from 1 which shall be assigned to the first byte of the first File Section, if any. The numbering shall continue through successive bytes of that File Section and then through successive bytes of each successive File Section, if any, of the file.

The numbering shall end with a number equal to the sum of the number of bytes in all File Sections of the file.

6.5.3 Contents of a file

The information in a file shall be interpreted according to the relevant standards for the coded representation of information.

NOTE - The identification of these standards is the subject of an agreement between the originator and the recipient of the file.

6.5.4 Associated File

An Associated File has a relationship not specified by this International Standard to another file that has been assigned the same File Identifier (see 7.5) as that of the Associated File in the same directory.

6.6 Volume Set

A Volume Set shall be the set of volumes on which a set of files is recorded.

A Volume Set shall consist of one or more volumes having common volume set identification and identifying the same coded graphic character sets for use within selected descriptor fields (see 7.4). All volumes in a Volume Set shall be numbered consecutively starting from 1.

A Volume Group within a Volume set shall consist of one or more consecutively numbered volumes the contents of which are established at the same time. The sequence number of the volume that has the highest sequence number within the Volume Group shall be the assigned Volume Set Size.

Each volume of a Volume Set shall contain a description of all the directories and files that are recorded on those volumes the sequence number of which are less than, or equal to, the assigned Volume Set Size of the volume.

NOTE - Such description recorded on a volume shall supersede the description recorded on any volume of the Volume Set having a lower assigned Volume Set Size.

The Logical Block Size shall be the same for all volumes of a Volume Set.

6.7 Volume Descriptors

A Volume Descriptor shall be one of the following types:

• Primary Volume Descriptor
• Supplementary Volume Descriptor
• Enhanced Volume Descriptor
• Volume Partition Descriptor
• Boot Record
• Volume Descriptor Set Terminator

6.7.1 Volume Descriptor Set

A Volume Descriptor Set shall be a sequence of volume descriptors recorded in consecutively numbered Logical Sectors starting with the Logical Sector with Logical Sector Number 16. Each successive Volume Descriptor shall be recorded in the Logical Sector with the next higher Logical Sector Number than that of the Logical Sector in which the previous Volume Descriptor is recorded. The sequence shall consist of two or more volume descriptors consecutively recorded as follows.

6.7.1.1 The sequence shall contain one Primary Volume Descriptor (see 8.4) recorded at least once.

The Primary Volume Descriptor shall describe the Volume Space, and identify the attributes of the volume, the locations of a Root Directory and of a group of Path Tables, and the number of volumes in the Volume Set.

6.7.1.2 The sequence may contain zero or more Supplementary Volume Descriptors (see 8.5) each recorded at least once.

A Supplementary Volume Descriptor shall describe the Volume Space, and identify the attributes of the volume, the locations of a Root Directory and of group Path Tables, and the number of volumes in the Volume Set. It shall also identify the coded graphic character set used within selected fields of this descriptor, and of the fields in associated File Descriptors, Directory Descriptors and Path Tables.

6.7.1.3 The sequence may contain zero or more Enhanced Volume Descriptors (see 8.5) each recorded at least once.

An Enhanced Volume Descriptor shall describe the Volume Space, and identify the attributes of the volume, the locations of a Root Directory and of group Path Tables, and the number of volumes in the Volume Set. It shall also identify the coded graphic character set used within selected fields of this descriptor, and of the fields in associated File Descriptors, Directory Descriptors and Path Tables.

6.7.1.4 The sequence may contain zero or more Volume Partition Descriptors (see 8.6).

A Volume Partition Descriptor shall identify a Volume Partition within the Volume Space, its position and size, and its attributes.

6.7.1.5 The sequence may contain zero or more Boot Records (see 8.2).

A Boot Record shall contain information which may be used to achieve a specific state in a receiving system or an application program.

6.7.1.6 The sequence shall be terminated by the recording of one or more Volume Descriptor Set Terminators (see 8.3).

6.8 Directory structure

6.8.1 Directory

A directory shall be recorded as a file containing a set of records each of which identifies a File Section or another directory. A directory shall not be recorded as an Associated File, shall not be recorded in interleaved mode and shall consist of only one File Section.

The identification of a file shall be different from the identification of any other file, unless the file is an Associated File (see 6.5.3), or of any directory identified in the same directory. The identification of a directory shall be different from the identification of any file or of any other directory identified in the same directory.

The first Logical Block of the Extent in which a directory is recorded shall have a Logical Block Number which is the lowest Logical Block Number in the Logical Sector that contains that Logical Block.

6.8.1.1 Directory Record

A Directory Record shall contain

• information to locate a File Section;
• information to locate any Extended Attribute Record associated with the File Section;
• the identification of the file;
• certain attributes of the file;
• certain attributes of the File Section.

The first or only Directory Record recorded in a Logical Sector shall begin at the first byte of the first Data Field of that Logical Sector. Each subsequent Directory Record recorded in that Logical Sector shall begin at the byte immediately following the last byte of the preceding Directory Record in that Logical Sector. Each Directory Record shall end in the Logical Sector in which it begins. Unused positions after the last Directory Record in a Logical Sector shall be set to (OO).

6.8.1.2 Order of Directory Records

The records in a Directory shall be ordered according to 9.3.

6.8.1.3 Directory length

The length of a directory shall be the sum of

• the lengths of all Directory Records in the directory;
• the number of unused positions after the last Directory Record in all Logical Sectors in which the directory is recorded.

6.8.2 Directory Hierarchies

A Directory Hierarchy shall be a set of directories related to each other as follows.

The root of the hierarchy, called the Root Directory, shall be a directory identified in a Primary Volume Descriptor, Supplementary Volume Descriptor or Enhanced Volume Descriptor.

Each directory, other than the Root Directory, shall be identified by a record in another directory.

A directory identifying another directory shall be called the Parent Directory of the identified directory. Each directory shall contain a record which identifies its Parent Directory. Different directories may have the same Parent Directory.

A hierarchical relationship shall exist between the Root Directory and all other directories:

The hierarchy shall consist of a number of levels (i.e. for n levels: level 1, level 2,..., level n). The Root Directory shall be the one and only directory at level 1 of the hierarchy.

If a directory is at level m of the hierarchy, its Parent Directory shall be at level (m-1). The Parent Directory of the Root Directory shall be the Root Directory.

6.8.2.1 Depth of Directory Hierarchy

For a Directory Hierarchy identified in a Primary Volume Descriptor or in a Supplementary Volume Descriptor, the number of levels in the hierarchy shall not exceed eight. In addition, for each file recorded, the sum of the following shall not exceed 255:

• the length of the File Identifier (see 7.5.2);
• the length of the Directory Identifiers (see 7.6.3) of all relevant directories;
• the number of relevant directories.

For a Directory Hierarchy identified in an Enhanced Volume Descriptor, the number of levels in the hierarchy may exceed eight.

6.8.2.2 Identification of directories

• the first Directory Record of the Root Directory shall describe the Root Directory and shall have a Directory Identifier consisting of a single (OO) byte;
• the second Directory Record of the Root Directory shall describe the Root Directory and shall have a Directory Identifier consisting of a single (O1) byte;
• a Directory Record describing the Root Directory shall be contained in the Root Directory field of the volume descriptor that identifies the directory hierarchy.

For each directory other than the Root Directory

• the first Directory Record of the directory shall describe that directory and shall have a Directory Identifier consisting of a single (OO) byte;
• the second Directory Record of the directory shall describe the Parent Directory for that directory and shall have a Directory identifier consisting of a single (O1) byte;
• a Directory Record in its Parent Directory shall describe the directory.

6.8.3 Relation of Directory Hierarchies

One or more Directory Hierarchies shall be recorded on a volume.

A Directory Hierarchy shall be identified in the Primary Volume Descriptor.

Each additional Directory Hierarchy shall be identified in a Supplementary Volume Descriptor or an Enhanced Volume Descriptor.

The directories within each hierarchy shall identify zero or more of the files that are recorded in those volumes, the sequence numbers of which are less than, or equal to, the assigned Volume Set Size of the volume.

A directory shall not be a part of more than one Directory Hierarchy.

6.9 Path Table

A Path Table recorded on a volume of a Volume Set shall contain a set of records describing a directory hierarchy for those volumes of the Volume Set the sequence numbers of which are less than, or equal to, the assigned Volume Set Size of the volume.

For each directory in the directory hierarchy other than the Root Directory, the Path Table shall contain a record which identifies the directory, its Parent Directory and its location. The records in a Path Table shall be numbered starting from 1. The first record in the Path Table shall identify the Root Directory and its location.

The directory number of a directory shall be the ordinal number of the Path Table Record that identifies the directory.

6.9.1 Order of Path Table Records

The records in a Path Table shall be ordered by the following criteria in descending order of significance:

• in ascending order according to level in the directory hierarchy;
• in ascending order according to the directory number of the Parent Directory of the directory identified by the record;
• in ascending order according to the relative value of the Directory Identifier field in the record, where the Directory Identifiers shall be valued as follows:
  • If two Directory Identifiers do not contain the same number of byte positions, the shorter Directory Identifier shall be treated as if it were padded on the right with all padding bytes set to (2O), and as if both Directory Identifiers contained the identical number of byte positions.
  • After any padding necessary to treat the Directory Identifiers as if they were of equal length, the characters in the corresponding byte positions, starting with the first position, of the Directory Identifiers are compared until a byte position is found that does not contain the same character in both Directory Identifiers. The greater Directory Identifier is the one that contains the character with the higher code position value in the coded graphic character set used to interpret the Directory Identifier of the Path Table Record.

6.9.2 Path Table Group

A Path Table shall be either a Type L Path Table or a Type M Path Table.

In a Type L Path Table, a numerical value shall be recorded according to 7.2.1 if represented as a 16-bit number and according to 7.3.1 if represented as a 32-bit number.

In a Type M Path Table, a numerical value shall be recorded according to 7.2.2 if represented as a 16-bit number and according to 7.3.2 if represented as a 32-bit number.

A Path Table Group shall comprise one or two identical Type L Path Tables and one or two identical Type M Path Tables.

6.9.3 Recorded Occurrences of the Path Table

One or more Path Table Groups shall be recorded on a volume. The Primary Volume Descriptor shall identify the size and locations of the constituent Path Tables of a Path Table Group. These Path Tables shall identify the directories in the Directory Hierarchy which is identified by the Primary Volume Descriptor.

Corresponding to each additional Directory Hierarchy recorded on a volume an additional Path Table Group shall be recorded on the volume. For each such Path Table Group the corresponding Supplementary Volume Descriptor shall identify the size and locations of its constituent Path Tables. These Path Tables shall identify the directories in the corresponding Directory Hierarchy.

6.9.4 Consistency of Path Tables between volumes of a Volume Group

6.9.4.1 The contents of a Type L Path Table identified in a Primary Volume Descriptor shall be identical with the contents of any other Type L Path Table identified in a Primary Volume Descriptor on a volume of the same Volume Group.

The contents of a Type M Path Table identified in a Primary Volume Descriptor shall be identical with the contents of any other Type M Path Table identified in a Primary Volume Descriptor on a volume of the same Volume Group.

6.9.4.2 The contents of a Type L Path Table identified in a Supplementary Volume Descriptor shall be identical with the contents of any other Type L Path Table identified in a Supplementary Volume Descriptor, having the same volume set identification and identifying the same coded graphic character set for use within selected descriptor fields (see 7.4), on a volume of the same Volume Group.

The contents of a Type M Path Table identified in a Supplementary Volume Descriptor shall be identical with the contents of any other Type M Path Table identified in a Supplementary Volume Descriptor, having the same volume set identification and identifying the same coded graphic character sets for use within selected descriptor fields (see 7.4), on a volume of the same Volume Group.

6.10 Record structure

The information in a file may be organized as a set of records according to this clause.

6.10.1 Characteristics

A record shall be a sequence of bytes treated as a unit of information.

The length of a record shall be the number of bytes in the record.

A record shall be either a fixed-length record, or a variable-length record.

All records in a file shall be either fixed-length records or variable-length records.

6.10.2 Measured Data Units (MDU)

6.10.2.1 Contents of an MDU

A Measured Data Unit shall contain either a fixed-length record or a variable-length record. An MDU shall comprise an even number of bytes.

6.10.2.2 Relationship to File

Each MDU shall comprise a set of successive bytes of the file. The first or only MDU shall begin at the first byte of the file. Each successive MDU shall begin at the byte in the file immediately following the last byte of the preceding MDU.

6.10.3 Fixed-length records

A fixed-length record shall be a record contained in a file that is assigned to contain records that must have the same length.

A fixed-length record shall be contained in an MDU. The MDU shall consist of the fixed-length record, immediately followed by a (OO) byte if necessary to give the MDU an even length.

The minimum assigned length of a fixed-length record shall be 1.

6.10.4 Variable-length records

A variable-length record shall be a record contained in a file that is assigned to contain records that may have different lengths. The value recorded in the Record Format field of an Extended Attribute Record for a file containing variable-length records shall contain the same value as that recorded in the Record Format field of any other Extended Attribute Record of that same file.

A variable-length record shall be contained in an MDU. The MDU shall consist of a Record Control Word (RCW) immediately followed by the variable-length record, immediately followed by a (OO) byte if necessary to give the MDU an even length.

The RCW shall specify as a 16-bit number the length of the record. The RCW shall be recorded according to

• 7.2.1, if the value in the Record Format field of the Extended Attribute Record associated with the File Section is 2, or
• 7.2.2, if the value in the Record Format field of the Extended Attribute Record associated with the File Section is 3.

A maximum record length shall be assigned for a file. The length of any record in the file shall not exceed this value. The assigned maximum record length shall be in the range 1 to 32 767.

The minimum length of a variable-length record shall be O.

7 Recording of descriptor fields

7.1 8-Bit numerical values

A numerical value represented in binary notation by an 8-bit number shall be recorded in a field of a descriptor in one of the following two formats. The applicable format is specified in the description of the descriptor fields.

7.1.1 8-Bit unsigned numerical values

An unsigned numerical value shall be represented in binary notation by an 8-bit number recorded in a one-byte field.

7.1.2 8-Bit signed numerical values

A signed numerical value shall be represented in binary notation by an 8-bit two's complement number recorded in a one-byte field.

7.2 16-Bit numerical value

A numerical value represented in binary notation by a 16-bit number shall be recorded in a field of a descriptor in one of the following three formats. The applicable format is specified in the description of the descriptor fields.

7.2.1 Least significant byte first

A numerical value represented by the hexadecimal representation (wx yz) shall be recorded in a two-byte field as (yz wx).

NOTE - For example, the decimal number 4 66O has (12 34) as its hexadecimal representation and is recorded as (34 12).

7.2.2 Most significant byte first

A numerical value represented by the hexadecimal representation (wx yz) shall be recorded in a two-byte field as (wx yz).

NOTE - For example, the decimal number 4 660 has (12 34) as its hexadecimal representation and is recorded as (12 34).

7.2.3 Both-byte orders

A numerical value represented by the hexadecimal representation (wx yz) shall be recorded in a four- byte field as (yz wx wx yz).

NOTE - For example, the decimal number 4 660 has (12 34) as its hexadecimal representation and is recorded as (34 12 12 34).

7.3 32-bit numerical values

A numerical value represented in binary notation by a 32-bit number shall be recorded in a field of a descriptor in one of the following three formats. The applicable format is specified in the description of the descriptor fields.

7.3.1 Least significant byte first

A numerical value represented by the hexadecimal representation (st uv wx yz) shall be recorded in a four-byte field 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).

7.3.2 Most significant byte first

A numerical value represented by the hexadecimal representation (st uv wx yz) shall be recorded in a four-byte field as (st uv wx yz).

NOTE - For example, the decimal number 305 419 896 has (12 34 56 78) as its hexadecimal representation and is recorded as (12 34 56 78).

7.3.3 Both-byte orders

A numerical value represented by the hexadecimal representation (st uv wx yz) shall be recorded in an eight-byte field as (yz wx uv st st uv wx yz).

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 12 34 56 78).

7.4 Character sets and coding

7.4.1 d-characters and a-character

Except as specified in 7.4.4, the characters in the descriptors shall be coded according to ISO/IEC 646 (see Annex A).

The 37 characters in the following positions of the International Reference Version are referred to as d-characters:

• 3/0 to 3/9
• 4/1 to 5/10
• 5/15

The 57 characters in the following positions of the International Reference Version are referred to as a-characters:

• 2/0 to 2/2
• 2/5 to 2/15
• 3/0 to 3/15
• 4/1 to 4/15
• 5/0 to 5/10
• 5/15

The applicable set of characters is specified in the description of the descriptor fields.

7.4.2 c-characters

The characters of the coded graphic character sets identified by the escape sequences in a Supplementary Volume Descriptor are referred to as c-characters.

7.4.2.1 a1-Characters

A subset of the c-characters will be referred to as a1-characters. This subset shall be subject to agreement between the originator and the recipient of the volume.

7.4.2.2 d1-characters

A subset of the a1-characters will be referred to as d1-characters. This subset shall be subject of agreement between the originator and the recipient of the volume.

7.4.3 Separators and Filler

7.4.3.1 Separators

The characters separating the components of a File Identifier within a Directory Hierarchy that is identified in a Primary Volume Descriptor or in a Supplementary Volume Descriptor shall be

• SEPARATOR 1 represented by the bit combination (2E)
• SEPARATOR 2 represented by the bit combination (3B)

A File Identifier within a Directory Hierarchy that is identified in an Enhanced Volume Descriptor shall not be separated into components.

SEPARATORS are not specified for a File Identifier within a Directory Hierarchy that is identified in an Enhanced Volume Descriptor.

7.4.3.2 Filler

The character filling any byte position which is specified by this International Standard to be characters shall be referred to as FILLER.

Within a volume that is identified by a Primary Volume Descriptor or by a Supplementary Volume Descriptor, the bit combination of FILLER shall be (20).

Within a volume that is identified by an Enhanced Volume Descriptor, the bit combination of FILLER shall be subject to agreement between the originator and the recipient of the volume.

7.4.4 Use of characters in descriptor fields

The characters in the fields of the following descriptors shall be a-characters or d-characters as specified in clause 9.

• Directory records within a Directory Hierarchy that is identified in a Primary Volume Descriptor;
• Path Table records within a Path Table Group identified in a Supplementary Volume Descriptor;
• Extended Attribute records identified in a directory of a Directory Hierarchy that is identified in a Primary Volume Descriptor.

The character in the fields of the following descriptors shall be a1-characters or d1-characters as specified in clause 9.

• Directory record within a Directory Hierarchy that is identified in a Supplementary Volume Descriptor or in an Enhanced Volume Descriptor;
• Path Table records within a Directory Group identified in a Supplementary Volume Descriptor or in an Enhanced Volume Descriptor;
• Extended Attribute records identified in a directory of a Directory Hierarchy that is identified in a Supplementary Volume Descriptor or in an Enhanced Volume Descriptor.

7.4.5 Justification of characters

In each fixed-length field the content of which is specified by this International Standard to be characters, the characters shall be left-justified and any remaining positions on the right shall be set to FILLER.

7.5 File Identifier

7.5.1 File Identifier format

A File Identifier shall consist of the following sequence:

• File Name: A sequence of zero or more d-characters or d1-characters;
• SEPARATOR 1;
• File Name Extension: A sequence of zero or more d-characters or d1-characters;
• SEPARATOR 2;
• File Version Number: Digits representing a number from 1 to 32 767.

Within a Directory Hierarchy that is identified in a Primary Volume Descriptor or in a Supplementary Volume Descriptor, this sequence shall meet the following requirements:

• If no characters are specified for the File Name then the File Name Extension shall consist of at least one character.
• If no characters are specified for the File Name Extension then the File Name shall consist of at least one character.
• The sum of the following shall not exceed 30:
  • if there is a File Name, the length of the File Name;
  • if there is a File Name Extension, the length of the File Name Extension.

Within a Directory Hierarchy that is identified in an Enhanced Volume Descriptor, this sequence shall meet the following requirements:

• the Length of File Name shall not exceed 207.
• no SEPARATORs are specified.
• no File Name Extension is present.
• no File Version Number is present.

Within a Directory Hierarchy that is identified in an Enhanced Volume Descriptor, a File Identifier shall not be specified as certain character sequences. These sequences shall be subject to agreement between the originator and recipient of the volume.

NOTE - 207 (the maximum length of the File Name) is the 254 (the maximum Directory Record Length), subtracted by 33 (the minimum length of Directory Record excluding the File Identifier) and by 14 (the CD-ROM XA System Use Extension Information) (see PHILIPS and SONY, System Description CD-ROM XA, 1991-05).

7.5.2 File Identifier length

The length of the File Identifier shall be the sum of the following:

• if there is a File Name, the length of the File Name,
• if there is a File Name Extension, the length of the File Name Extension,
• if there is a File Version Number, the number of digits in the File Version Number,
• if SEPARATORs are specified, 2(the number of SEPARATORs).

7.6 Directory Identifier

7.6.1 Directory Identifier Format

A Directory Identifier shall consist of a sequence of one or more d-characters or d1-characters (see 7.4.4), except as specified in 7.6.2.

Within a volume identified by an Enhanced Volume Descriptor, a Directory Identifier can be sequence of characters rather than d-characters or d1-characters. The sequence shall be subject to agreement between the originator and recipient of the volume.

7.6.2 Reserved Directory Identifiers

The Root Directory shall be identified by Directory Identifier consist of a single (00) byte.

As specified in 6.8.2.2, certain Directory Identifiers shall consist of a single (00) byte or a single (01) byte.

7.6.3 Directory Identifier length

Within a Directory Hierarchy that is identified in a Primary Volume Descriptor or in a Supplementary Volume Descriptor, the length of a Directory Identifier shall not exceed 31.

Within a Directory Hierarchy that is identified in an Enhanced Volume Descriptor, the length of a Directory Identifier shall not exceed 207.

8 Volume descriptors

The Volume Descriptors shall identify the volume, the partitions recorded on the volume, the volume creator(s), certain attributes of the volume, the location of other recorded descriptors and the version of the standard which applies to the volume descriptor.

8.1 Format of a Volume Descriptor

8.1.1 Volume Descriptor Type (BP 1)

This field shall specify as an 8-bit number the Volume Descriptor Type.

Number O shall mean that the Volume Descriptor is a Boot Record;

Number 1 shall mean that the Volume Descriptor is a Primary Volume Descriptor;

Number 2 shall mean that the Volume Descriptor is a Supplementary Volume Descriptor or an Enhanced Volume Descriptor;

Number 3 shall mean that the Volume Descriptor is a Volume Partition Descriptor;

Numbers 4 to 254 are reserved for future standardization;

Number 255 shall mean that the Volume Descriptor is a Volume Descriptor Set Terminator.

This field shall be recorded according to 7.1.1.

8.1.2 Standard Identifier (BP 2 to 6)

This field shall specify an identification of this International Standard.

The characters in this field shall be CDOO1.

8.1.3 Volume Descriptor Version (BP 7)

This field shall specify as an 8-bit number the version of the specification of the Volume Descriptor.

The content and the interpretation of this field shall depend on the content of the Volume Descriptor Type field.

This field shall be recorded according to 7.1.1.

8.1.4 Depends on Volume Descriptor Type (BP 8 to 2 048)

The content and the interpretation of this field shall depend on the Volume Descriptor Type field.

8.2 Boot Record

The Boot Record shall identify a system which can recognize and act upon the content of the field reserved for boot system use in the Boot Record, and shall contain information which is used to achieve a specific state for a system or for an application.

8.2.1 Volume Descriptor Type (BP 1)

This field shall specify an 8-bit number indicating that the Volume Descriptor is a Boot Record.

The number in this field shall be O.

This field shall be recorded according to 7.1.1.

8.2.2 Standard Identifier (BP 2 to 6)

This field shall specify an identification of this International Standard.

The characters in this field shall be CDOO1.

8.2.3 Volume Descriptor Version (BP 7)

This field shall specify as an 8-bit number the version of the specification of the Boot Record structure.

1 shall indicate the structure of this International Standard.

This field shall be recorded according to 7.1.1.

8.2.4 Boot System Identifier (BP 8 to 39)

This field shall specify an identification of a system which can recognize and act upon the content of the Boot Identifier and Boot System Use fields in the Boot Record.

The characters in this field shall be a-characters.

8.2.5 Boot Identifier (BP 40 to 71)

This field shall specify an identification of the boot system specified in the Boot System Use field of the Boot Record.

The characters in this field shall be a-characters.

8.2.6 Boot System Use (BP 72 to 2 048)

This field shall be reserved for boot system use. Its contents is not specified by this International Standard.

8.3 Volume Descriptor Set Terminator

The recorded set of Volume Descriptors shall be terminated by a sequence of one or more Volume Descriptor Set Terminators.

8.3.1 Volume Descriptor Type (BP 1)

This field shall specify an 8-bit number indicating that the Volume Descriptor is a Volume Descriptor Set Terminator.

The number in this field shall be 255.

This field shall be recorded according to 7.1.1.

8.3.2 Standard Identifier (BP 2 to 6)

This Field shall specify an identification of this International Standard.

The characters in this field shall be CDOO1.

8.3.3 Volume Descriptor Version (BP 7)

This field shall specify as an 8-bit number the version of the specification of the Volume Descriptor Set Terminator.

1 shall indicate the structure of this International Standard.

This field shall be recorded according to 7.1.1.

8.3.4 Reserved for future standardization (BP 8 to 2 048)

All bytes of this field shall be set to (OO).

8.4 Primary Volume Descriptor

The Primary Volume Descriptor shall identify the volume, a system which can recognize and act upon the content of the Logical Sectors with Logical Sector Numbers O to 15, the size of the Volume Space, the version of the standard which applies to the Volume Descriptor, the version of the specification which applies to the directory records and the Path Table records and certain attributes of the volume.

8.4.1 Volume Descriptor Type (BP 1)

This field shall specify an 8-bit number indicating that the volume descriptor is a Primary Volume Descriptor.

The number in this field shall be 1.

This field shall be recorded according to 7.1.1.

8.4.2 Standard Identifier (BP 2 to 6)

This field shall specify an identification of this International Standard.

The characters in this field shall be CDOO1.

8.4.3 Volume Descriptor Version (BP 7)

This field shall specify as an 8-bit number an identification of the version of the specification of the Primary Volume Descriptor.

1 shall indicate the structure of this International Standard.

This field shall be recorded according to 7.1.1.

8.4.4 Unused Field (BP 8)

This field shall be set to (OO).

8.4.5 System Identifier (BP 9 to 40)

This field shall specify an identification of a system which can recognize and act upon the content of the Logical Sectors with logical Sector Numbers O to 15 of the volume.

The characters in this field shall be a-characters.

8.4.6 Volume Identifier (BP 41 to 72)

This field shall specify an identification of the volume.

The characters in this field shall be d-characters.

8.4.7 Unused Field (BP 73 to 80)

All bytes of this Field shall be set to (OO).

8.4.8 Volume Space Size (BP 81 to 88)

This field shall specify as a 32-bit number the number of Logical Blocks in which the Volume Space of the volume is recorded.

This field shall be recorded according to 7.3.3.

8.4.9 Unused Field (BP 89 to 120)

All bytes of this field shall be set to (OO).

8.4.10 Volume Set Size (BP 121 to 124)

This field shall specify as a 16-bit number the assigned Volume Set Size of the volume.

This field shall be recorded according to 7.2.3.

8.4.11 Volume Sequence Number (BP 125 to 128)

This field shall specify as a 16-bit number the ordinal number of the volume in the Volume Set of which the volume is a member.

This field shall be recorded according to 7.2.3.

8.4.12 Logical Block Size (BP 129 to 132)

This field shall specify as a 16-bit number the size, in bytes, of a Logical Block.

This field shall be recorded according to 7.2.3.

8.4.13 Path Table Size (BP 133 to 140)

This field shall specify as a 32-bit number the length in bytes of a recorded occurrence of the Path Table identified by this Volume Descriptor.

This field shall be recorded according to 7.3.3.

8.4.14 Location of Occurrence of Type L Path Table (BP 141 to 144)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an occurrence of the Path Table. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the least significant byte first.

This field shall be recorded according to 7.3.1.

8.4.15 Location of Optional Occurrence of Type L Path Table (BP 145 to 148)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an optional occurrence of the Path Table. If the value is O, it shall mean that the Extent shall not be expected to have been recorded. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the least significant byte first.

This field shall be recorded according to 7.3.1.

8.4.16 Location of Occurrence of Type M Path Table (BP 149 to 152)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an occurrence of the Path Table. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the most significant byte first.

This field shall be recorded according to 7.3.2.

8.4.17 Location of Optional Occurrence of Type M Path Table (BP 153 to 156)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an optional occurrence of the Path Table. If the value is O, it shall mean that the Extent shall not be expected to have been recorded. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the most significant byte first.

This field shall be recorded according to 7.3.2.

8.4.18 Directory Record for Root Directory (BP 157 to 190)

This field shall contain an occurrence of the Directory Record for the Root directory.

This field shall be recorded according to 9.1.

8.4.19 Volume Set Identifier (BP 191 to 318)

This field shall specify an identification of the Volume Set of which the volume is a member.

The characters in this field shall be d-characters.

8.4.20 Publisher Identifier (BP 319 to 446)

This field shall specify an identification of the user who specified what shall be recorded on the Volume Group of which the volume is a member.

If the first byte is set to (5F), the remaining bytes of this field shall specify an identifier for a file containing the identification of the user. This file shall be described in the Root Directory. The File Name shall not contain more than eight d-characters and the File Name Extension shall not contain more than three d-characters.

If all bytes of this field are set to FILLER, it shall mean that no such user is identified.

The characters in this field shall be a-characters.

8.4.21 Data Preparer Identifier (BP 447 to 574)

This field shall specify an identification of the person or other entity which controls the preparation of the data to be recorded on the Volume Group of which the volume is a member.

If the first byte is set to (5F), the remaining bytes of this field shall specify an identifier for a file containing the identification of the data preparer. This file shall be described in the Root Directory. The File Name shall not contain more than eight d-characters and the File Name Extension shall not contain more than three d-characters.

If all bytes of this field are set to FILLER, it shall mean that no such data preparer is identified.

The characters in this field shall be a-characters.

8.4.22 Application Identifier (BP 575 to 702)

This field shall specify an identification of the specification of how the data are recorded on the Volume Group of which the volume is a member.

If the first byte is set to (5F), the remaining bytes of this field shall specify an identifier for a file containing the identification of the application. This file shall be described in the Root Directory. The File Name shall not contain more than eight d-characters and the File Name Extension shall not contain more than three d-characters.

If all bytes of this field are set to FILLER, it shall mean that no such application is identified.

The characters in this field shall be a-characters.

8.4.23 Copyright File Identifier (BP 703 to 739)

This field shall specify an identification for a file described by the Root Directory and containing a copyright statement for those volumes of the Volume Set the sequence numbers of which are less than, or equal to, the assigned Volume Set Size of the volume. If all bytes of this field are set to FILLER, it shall mean that no such file is identified.

The File Name of a Copyright File Identifier shall not contain more than 8 d-characters. The File Name Extension of a Copyright File Identifier shall not contain more than 3 d-characters.

The characters in this Field shall be d-characters, SEPARATOR 1 and SEPARATOR 2.

This field shall be recorded as specified in 7.5.

8.4.24 Abstract File Identifier (BP 740 to 776)

This Field shall specify an identification for a file described by the Root Directory and containing an abstract statement for those volumes of the Volume Set the sequence numbers of which are less than, or equal to, the assigned Volume Set Size of the volume. If all bytes of this field are set to FILLER, it shall mean that no such file is identified.

The File Name of an Abstract File Identifier shall not contain more than 8 d-characters. The File Name Extension of an Abstract File Identifier shall not contain more than 3 d-characters.

The characters in this Field shall be d-characters, SEPATATOR 1 and SEPARATOR 2.

The field shall be recorded as specified in 7.5.

8.4.25 Bibliographic File Identifier (BP 777 to 813)

This field shall specify an identification for a file described by the Root Directory and containing bibliographic records interpreted according to standards that are the subject of an agreement between the originator and the recipient of the volume. If all bytes of this field are set to FILLER, it shall mean that no such file is identified.

The File Name of a Bibliographic File Identifier shall not contain more than eight d-characters. The File Name Extension of a Bibliographic File identifier shall not contain more than three d-characters.

The characters in this field shall be d-characters, SEPARATOR 1 and SEPARATOR 2.

The field shall be recorded as specified in 7.5.

8.4.26 Volume Creation Date and Time (BP 814 to 830)

This field shall specify the date and the time of the day at which the information in the volume was created. It shall be recorded according to 8.4.26.1.

8.4.26.1 Date and Time Format

The date and time shall be represented by a 17-byte field recorded as follows.

If all characters in RBP 1 to 16 of this field are the digit ZERO and the number in RBP 17 is zero, it shall mean that the date and time are not specified.

8.4.27 Volume Modification Date and Time (BP 831 to 847)

This field shall specify the date and the time of the day at which the information in the volume was last modified.

This field shall be recorded according to 8.4.26.1.

8.4.28 Volume Expiration Date and Time (BP 848 to 864)

This field shall specify the date and the time of the day at which the information in the volume may be regarded as obsolete. If the date and time are not specified then the information shall not be regarded as obsolete.

This field shall be recorded according to 8.4.26.1.

8.4.29 Volume Effective Date and Time (BP 865 to 881)

This Field shall specify the date and the time of the day at which the information in the volume may be used. If the date and time are not specified then the information may be used at once.

This field shall be recorded according to 8.4.26.1.

8.4.30 File Structure Version (BP 882)

This field shall specify as an 8-bit number the version of the specification of the records of a directory and of a Path Table.

For a Primary Volume Descriptor or for a Supplementary Volume Descriptor, 1 shall indicate the structure of this International Standard.

For an Enhanced Volume Descriptor, 2 shall indicate the structure of this International Standard.

This field shall be recorded according to 7.1.1.

8.4.31 Reserved for future standardization (BP 883)

All bytes of this field shall be set to (OO).

8.4.32 Application Use (BP 884 to 1 395)

This field shall be reserved for application use. Its content is not specified by this International Standard.

8.4.33 Reserved for future standardization (BP 1 396 to 2 048)

This field shall be set to (00).

8.5 Supplementary Volume Descriptor and Enhanced Volume Descriptor

The Supplementary Volume Descriptor shall identify the volume, a system which can recognize and act upon the content of the Logical Sectors with Logical Sector Numbers O to 15, the size of the Volume Space, the version of the standard which applies to the Volume Descriptor, the version of the specification which applies to the directory records and the Path Table records, certain attributes of the volume and the coded graphic character sets used to interpret descriptor fields that contain characters.

The Enhanced Volume Descriptor shall identify the volume, a system which can recognize and act upon the content of the Logical Sectors with Logical Sector Numbers 0 to 15, the size of the Volume Space, the version of the standard which applies to the Volume Descriptor, the version of the specification which applies to the Directory Records and the Path Table Records, certain attributes of the volume and the coded graphic character sets used to interpret descriptor fields that contain characters.

Within a volume Descriptor Set the contents of the fields of this descriptor shall be identical with the contents of the corresponding fields in a Primary Volume Descriptor except for the following fields.

8.5.1 Volume Descriptor Type (BP 1)

This field shall specify an 8-bit number indicating that the Volume Descriptor is a Supplementary Volume Descriptor or is an Enhanced Volume Descriptor.

The number in this field shall be 2.

This field shall be recorded according to 7.1.1.

8.5.2 Volume Descriptor Version (BP 7)

This field shall specify as an 8-bit number an identification of the Version of the specification of the Supplementary Volume Descriptor or the Enhanced Volume Descriptor.

For a Supplementary Volume Descriptor, 1 shall indicate the structure of this International Standard.

For an Enhanced Volume Descriptor, 2 shall indicate the structure of this International Standard.

This field shall be recorded according to 7.1.1.

8.5.3 Volume Flags (BP 8)

The bits of this field shall be numbered from O to 7 starting with the least significant bit.

This field shall specify certain characteristics of the volume as follows.

Bit O:

• if set to ZERO, shall mean that the Escape Sequences field specifies only escape sequences registered according to ISO 2375;
• if set to ONE, shall mean that the Escape Sequences field specifies at least one escape sequence not registered according to ISO 2375.

Bits 1 to 7: These bits are reserved for future standardization and shall all be set to ZERO.

8.5.4 System Identifier (BP 9 to 40)

This Field shall specify an identification of a system which can recognize and act upon the content of the Logical Sectors with Logical Sector Numbers O to 15 of the volume.

The characters in this field shall be a1-characters.

8.5.5 Volume Identifier (BP 41 to 72)

This field shall specify an identification of the volume.

Within a Supplementary Volume Descriptor, the characters in this field shall be d1-characters.

Within an Enhanced Volume Descriptor, the characters in this field shall be subject to agreement between the originator and recipient of the volume.

8.5.6 Escape Sequences (BP 89 to 120)

This field shall specify one or more escape sequences according to ISO/IEC 2022 that designate the G0 graphic character set and, optionally, the G1 graphic character set to be used in an 8-bit environment according to ISO/IEC 2022 to interpret descriptor fields related to the Directory Hierarchy identified by this Volume Descriptor (see 7.4.4). If the G1 set is designated, it is implicitly invoked into columns 1O to 15 of the code table.

These escape sequences shall conform to ISO/IEC 2022, except that the ESCAPE character shall be omitted from each designating escape sequence when recorded in this Field. The first or only escape sequence shall begin at the first byte of the field. Each successive escape sequence shall begin at the byte in the field immediately following the last byte of the preceding escape sequence. Any unused positions following the last sequence shall be set to (OO).

If all the bytes of this field are set to (OO), it shall mean that the set of a1-characters is identical with the set of a-characters and that the set of d1-characters is identical with the set of d-characters. In this case both sets are coded according to ISO/IEC 646.

8.5.7 Path Table Size (BP 133 to 140)

This field shall specify as a 32-bit number the length in bytes of a recorded occurrence of the Path Table identified by this Volume Descriptor.

This field shall be recorded according to 7.3.3.

8.5.8 Location of Occurrence of Type L Path Table (BP 141 to 144)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an occurrence of the Path Table. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the least significant byte first.

This field shall be recorded according to 7.3.1.

8.5.9 Location of Optional Occurrence of Type L Path Table (BP 145 to 148)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an optional occurrence of the Path Table. If the value is O, it shall mean that the Extent shall not be expected to have been recorded. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the least significant byte first.

This field shall be recorded according to 7.3.1.

8.5.10 Location of Occurrence of Type M Path Table (BP 149 to 152)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an occurrence of the Path Table. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the most significant byte first.

This field shall be recorded according to 7.3.2.

8.5.11 Location of Optional Occurrence of Type M Path Table (BP 153 to 156)

This Field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent which contains an optional occurrence of the Path Table. If the value is O, it shall mean that the Extent shall not be expected to have been recorded. Multiple-byte numerical values in a record of this occurrence of the Path Table shall be recorded with the most significant byte first.

This field shall be recorded according to 7.3.2.

8.5.12 Directory Record for Root Directory (BP 157 to 190)

This field shall contain an occurrence of the Directory Record for the Root Directory.

This Field shall be recorded according to 9.1.

8.5.13 Volume Set Identifier (BP 191 to 318)

This Field shall specify an identification of the Volume Set of which the volume is a member.

Within a Supplementary Volume Descriptor, the characters in this field shall be d1-characters.

Within an Enhanced Volume Descriptor, the characters in this field shall be subject to agreement between the originator and recipient of the volume.

8.5.14 Publisher Identifier (BP 319 to 446)

This field shall specify an identification of the user who specified what shall be recorded on the Volume Group of which the volume is a member.

If the first byte is set to (5F), the remaining bytes of this field shall specify an identifier for a file containing the identification of the user. This file shall be described in the Root Directory.

If all bytes of this field are set to FILLER, it shall mean that no such user is identified.

The characters in this field shall be a1-characters.

8.5.15 Data Preparer Identifier (BP 447 to 574)

This field shall specify an identification of the person or other entity which controls the preparation of the data to be recorded on the Volume Group of which the volume is a member.

If the first byte is set to (5F), the remaining bytes of this field shall specify an identifier for a file containing the identification of the data preparer. This file shall be described in the Root Directory.

If all bytes of this field are set to FILLER, it shall mean that no such data preparer is identified.

The characters in this field shall be a1-characters.

8.5.16 Application Identifier (BP 575 to 702)

This field shall specify an identification of the specification of how the data are recorded on the Volume Group of which the volume is a member.

If the first byte is set to (5F), the remaining bytes of this field shall specify an identifier for a file containing the identification of the application. This file shall be described in the Root Directory.

If all bytes of this field are set to FILLER, it shall mean that no such application is identified.

The characters in this field shall be a1-characters.

8.5.17 Copyright File Identifier (BP 703 to 739)

This field shall specify an identification for a file described by the Root Directory and containing a copyright statement for those volumes of the Volume Set the sequence numbers of which are less than, or equal to, the assigned Volume Set Size of the volume. If all bytes of this field are set to FILLER, it shall mean that no such file is identified.

Within a Supplementary Volume Descriptor, the characters in this field shall be d1-characters, SEPARATOR 1 and SEPARATOR 2.

Within an Enhanced Volume Descriptor, the characters in this field shall be subject to agreement between the originator and recipient of the volume.

The field shall be recorded as specified in 7.5.

8.5.18 Abstract File Identifier (BP 740 to 776)

This field shall specify an identification for a file described by the Root Directory and containing an abstract statement for those volumes of the Volume Set the sequence numbers of which are less than, or equal to, the assigned Volume Set Size of the volume. If all bytes of this Field are set to FILLER, it shall mean that no such file is identified.

Within a Supplementary Volume Descriptor, the characters in this field shall be d1-characters, SEPARATOR 1 and SEPARATOR 2.

Within an Enhanced Volume Descriptor, the characters in this field shall be subject to agreement between the originator and recipient of the volume.

The field shall be recorded as specified in 7.5.

8.5.19 Bibliographic File Identifier (BP 777 to 813)

This field shall specify an identification for a file described by the Root Directory and contain bibliographic records interpreted according to standards that are the subject of an agreement between the originator and the recipient of the volume. If all bytes of this field are set to FILLER, it shall mean that no such file is identified.

Within a Supplementary Volume Descriptor, the characters in this field shall be d1-characters, SEPARATOR 1 and SEPARATOR 2.

Within an Enhanced Volume Descriptor, the characters in this field shall be subject to agreement between the originator and recipient of the volume.

The Field shall be recorded as specified in 7.5.

8.5.20 Application Use (BP 884 to 1 395)

This field shall be reserved for application use. Its content is not specified by this International Standard.

8.6 Volume Partition Descriptor

The Volume Partition Descriptor shall identify a volume partition within the Volume Space, a system which can recognize and act upon the content of fields reserved for system use in the Volume Descriptor, the position and size of the volume partition, and the version of the standard which applies to the Volume Descriptor. The contents of the volume partition are not specified by this International Standard.

8.6.1 Volume Descriptor Type (BP 1)

This field shall specify an 8-bit number indicating that the Volume Descriptor is a Volume Partition Descriptor.

The number in this Field shall be 3.

This Field shall be recorded according to 7.1.1.

8.6.2 Standard Identifier (BP 2-6)

This field shall specify an identification of this International Standard.

The characters in this field shall be CDOO1.

8.6.3 Volume Descriptor Version (BP 7)

This Field shall specify as an 8-bit number an identification of the version of the specification of the Volume Partition Descriptor.

1 shall indicate the structure of this International Standard.

This Field shall be recorded according to 7.1.1.

8.6.4 Unused Field (BP 8)

This Field shall be set to (OO).

8.6.5 System Identifier (BP 9 to 40)

This field shall specify an identification of a system which can recognize and act upon the content of the System Use field in the Volume Descriptor.

The characters in this field shall be a-characters.

8.6.6 Volume Partition Identifier (BP 41 to 72)

This field shall specify an identification of the Volume Partition.

The characters in this field shall be d-characters.

8.6.7 Volume Partition Location (BP 73 to 80)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Volume Partition.

This field shall be recorded according to 7.3.3.

8.6.8 Volume Partition Size (BP 81 to 88)

This field shall specify as a 32-bit number the number of Logical Blocks in which the Volume Partition is recorded.

This field shall be recorded according to 7.3.3.

8.6.9 System Use (BP 89 to 2 048)

This field shall be reserved for system use. Its content is not specified by this International Standard.

9 File and Directory Descriptors

9.1 Format of a Directory Record

Details of the format of a Directory Record are given in Table 8.

9.1.1 Length of Directory Record (LEN_DR) (BP 1)

This Field shall specify as an 8-bit number the length in bytes of the Directory Record.

This field shall be recorded according to 7.1.1.

9.1.2 Extended Attribute Record Length (BP 2)

This field shall contain an 8-bit number. This number shall specify the assigned Extended Attribute Record Length if an Extended Attribute Record is recorded. Otherwise this number shall be zero.

This field shall be recorded according to 7.1.1.

9.1.3 Location of Extent (BP 3 to 10)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent.

This field shall be recorded according to 7.3.3.

9.1.4 Data Length (BP 11 to 18)

This field shall specify as a 32-bit number the data length of the File Section.

This field shall be recorded according to 7.3.3.

NOTE - This number does not include the length of any Extended Attribute Record.

9.1.5 Recording Date and Time (BP 19 to 25)

This field shall indicate the date and the time of the day at which the information in the Extent described by the Directory Record was recorded.

The date and time shall be represented by seven 8-bit numbers each of which shall be recorded according to 7.1.1 as follows.

If all seven numbers are zero, it shall mean that the date and time are not specified.

9.1.6 File Flags (BP 26)

The bits of this field shall be numbered from O to 7 starting with the least significant bit.

If this Directory Record identifies a directory then bit positions 2, 3 and 7 shall be set to ZERO.

If no Extended Attribute Record is associated with the File Section identified by this Directory Record then bit positions 3 and 4 shall be set to ZERO.

This field shall specify certain characteristics of the file as follows.

9.1.7 File Unit Size (BP 27)

This field shall contain an 8-bit number. This number shall specify the File Unit Size for the File Section if the File Section is recorded in interleaved mode. Otherwise this number shall be zero.

This field shall be recorded according to 7.1.1.

9.1.8 Interleave Gap Size (BP 28)

This field shall contain an 8-bit number. This number shall specify the Interleave Gap Size for File Section if the File Section is recorded in interleaved mode. Otherwise this number shall be zero.

This field shall be recorded according to 7.1.1.

9.1.9 Volume Sequence Number (BP 29 to 32)

This field shall specify as a 16-bit number the ordinal number of the volume in the Volume Set on which the Extent described by this Directory Record is recorded.

This field shall be recorded according to 7.2.3.

9.1.10 Length of File Identifier (LEN_FI) (BP 33)

This field shall specify as an 8-bit number the length in bytes of the File Identifier field of the Directory Record.

This field shall be recorded according to 7.1.1.

9.1.11 File Identifier [BP 34 to (33+LEN_FI)]

The interpretation of this field depends as follows on the setting of the Directory bit of the File Flags field.

If set to ZERO, shall mean:

• The field shall specify an identification for the file.
• The characters in this field shall be d-characters or d1-characters, SEPARATOR 1, SEPARATOR 2.
• The field shall be recorded as specified in 7.5.

If set to ONE, shall mean:

• The field shall specify an identification for the directory.
• The characters in this field shall be d-characters or d1-characters, or only a (OO) byte, or only a (O1) byte.
• The field shall be recorded as specified in 7.6.

9.1.12 Padding Field [BP (34+LEN_FI)]

This field shall be present in the Directory Record only if the number in the Length of the File Identifier field is an even number.

If present, this Field shall be set to (OO).

9.1.13 System Use [BP (LEN_DR-LEN_SU+1) to LEN_DR]

This field shall be optional. If present, this field shall be reserved for system use. Its content is not specified by this International Standard. If necessary, so that the Directory Record comprises an even number of bytes, a (OO) byte shall be added to terminate this field.

9.2 Consistency of File Attributes between Directory Records of a File

The following fields of each Directory Record for the same file shall contain the same values:

• Existence bit of the File Flags field;
• Directory bit of the File Flags Field;
• Associated File bit of the File Flags Field;
• Record bit of the File Flags field;
• Reserved bits of the File Flags field;
• Length of File Identifier field;
• File Identifier field;
• Padding field.

9.3 Order of Directory Records

The records of a Directory shall be ordered according to the relative value of the File Identifier field by the following criteria in descending order of significance:

a) in ascending order according to the relative value of File Name, where File Names shall be valued as follows:

• If two File Names have the same content in all byte positions, then these two File Names are said to be equal in value.
• if two File Names do not contain the same number of byte positions, the shorter File Name shall be treated as if it were padded on the right with all padding bytes set to FILLER and as if both File Names contained the identical number of byte positions.
• After any padding necessary to treat the File Names as if they were of equal length, the characters in the corresponding byte positions, starting with the first position, of the File Names are compared until a byte position is found that does not contain the same character in both File Names. The greater File Name is the one that contains the character with the higher code position value in the coded graphic character set used to interpret the File Identifier field of the Directory Record.

b) in ascending order according to the relative value File Name Extensions, where File Name Extensions shall be valued as follows:

• If two File Name Extensions have the same content in all byte positions, then these two File Name Extensions are said to be equal in value.
• If two File Name Extensions do not contain the same number of byte positions, the shorter File Name Extension shall be treated as if it were padded on the right with all padding bytes set to FILLER and as if both File Name Extensions contained the identical number of byte positions.
• After any padding necessary to treat the File Name Extensions as if they were of equal length, the characters in the corresponding byte positions, starting with the first position, of the File Name Extensions are compared until a byte position is found that does not contain the same character in both File Name Extensions. The greater File Name Extension is the one that contains the character with the higher code position value in the coded graphic character set used to interpret the File Identifier field of the Directory Record.

c) in descending order according to the relative value of File Version Number, where File Version Numbers shall be valued as follows:

• If two File Version Numbers have the same content in all byte positions, then these two File Version Numbers are said to be equal in value.
• If two File Version Numbers do not contain the same number of byte positions, the shorter File Version Number shall be treated as if it were padded on the left with all padding bytes set to (3O) and as if both File Version Numbers contained the identical number of byte positions.
• After any padding necessary to treat the File Version Numbers as if they were of equal length, the characters in the corresponding byte positions, starting with the first position, of the File Version Numbers are compared until a byte position is found that does not contain the same character in both File Version Numbers. The greater File Version Number is the one that contains the character with the higher code position value in the coded graphic character set used to interpret the File Identifier field of the Directory Record.

d) in descending order according to the value of the Associated File bit of the File Flags field.

e) The order of the File Sections of the file.

9.4 Format of a Path Table Record

9.4.1 Length of Directory Identifier (LEN_DI) (BP 1)

This field shall specify as an 8-bit number the length in bytes of the Directory Identifier field of the Path Table Record.

This field shall be recorded according to 7.1.1.

9.4.2 Extended Attribute Record Length (BP 2)

This field shall contain an 8-bit number. This number shall specify the assigned Extended Attribute Record Length if an Extended Attribute Record is recorded. Otherwise this number shall be zero.

This field shall be recorded according to 7.1.1.

9.4.3 Location of Extent (BP 3 to 6)

This field shall specify as a 32-bit number the Logical Block Number of the first Logical Block allocated to the Extent in which the directory is recorded.

This field shall be recorded according to 7.3.

9.4.4 Parent Directory Number (BP 7 to 8)

This field shall specify as a 16-bit number the record number in the Path Table for the parent directory of the directory.

This field shall be recorded according to 7.2.

9.4.5 Directory Identifier [BP 9 to (8+LEN_DI)]

This field shall specify an identification for a directory.

The characters in this field shall be d-characters or d1-characters or only a (OO) byte.

This field shall be recorded as specified in 7.6.

9.4.6 Padding Field [BP (9+LEN_DI)]

This field shall be present in the Path Table Record only if the number in the Length of Directory Identifier field is an odd number.

If present, this field shall be set to (OO).

9.5 Format of an Extended Attribute Record

If present, an Extended Attribute Record shall be recorded over at least one Logical Block.

9.5.1 Owner Identification (BP 1 to 4)

This Field shall specify as a 16-bit number an identification of the file owner who is a member of the group identified by the Group Identification field of the Extended Attribute Record.

If the number in this field is O, this shall indicate that there is no owner identification specified for the file. In this case, the Group Identification field shall contain zero.

This field shall be recorded according to 7.2.3.

9.5.2 Group Identification (BP 5 to 8)

This field shall specify as a 16-bit number an identification of the group of which the file owner is a member.

The values for this number from 1 to a number subject to agreement between the data preparer and receiving system shall identify the group as belonging to the class of user referred to as System.

If the number in this field is O, this shall indicate that there is no group identification specified for the file. In this case, the Owner Identification field shall contain zero.

This field shall be recorded according to 7.2.3.

9.5.3 Permissions (BP 9 to 10)

The bits of this 16-bit field shall be numbered from O to 15 starting with the least significant bit of the byte recorded in byte position 1O.

Bits O to 3 may be ignored in interchange.

If requested by the owner, bits 4 to 7 may be ignored in interchange.

This field shall specify access permission for certain classes of users as follows.

9.5.4 File Creation Date and Time (BP 11 to 27)

This field shall specify the date and the time of the day at which the information in the file was created.

This field shall be recorded according to 8.4.26.1.

9.5.5 File Modification Date and Time (BP 28 to 44)

This field shall specify the date and the time of the day at which the information in the file was last modified.

This field shall be recorded according to 8.4.26.1.

9.5.6 File Expiration Date and Time (BP 45-61)

This field shall specify the date and the time of the day at which the information in the file may be regarded as obsolete. If the date and time are not specified then the information shall not be regarded as obsolete.

This field shall be recorded according to 8.4.26.1.

9.5.7 File Effective Date and Time (BP 62-78)

This field shall specify the date and the time of the day at which the information in the file may be used. If the date and time are not specified then the information may be used at once.

This field shall be recorded according to 8.4.26.1.

9.5.8 Record Format (BP 79)

This field shall contain an 8-bit number specifying the format of the information in the file.

Number O shall mean that the structure of the information recorded in the file is not specified by this Field;

Number 1 shall mean that the information in the file is a sequence of fixed-length records (see 6.10.3);

Number 2 shall mean that the information in the file is a sequence of variable-length records (see 6.10.4), in which the RCW is recorded according to 7.2.1;

Number 3 shall mean that the information in the file is a sequence of variable-length records (see 6.10.4), in which the RCW is recorded according to 7.2.2.

Numbers 4 to 127 are reserved for future standardization.

Numbers 128 to 255 are reserved for system use.

This field shall be recorded according to 7.1.1.

9.5.9 Record Attributes (BP 80)

This field shall contain an 8-bit number specifying certain processing of the records in a file when they are displayed on a character-imaging device.

Number O shall mean that each record shall be preceded by a LINE FEED character and followed by a CARRIAGE RETURN character;

Number 1 shall mean that the first byte of a record shall be interpreted as specified in ISO/IEC 1539-1 for vertical spacing;

Number 2 shall mean that the record contains the necessary control information.

Numbers 3 to 255 are reserved for future standardization.

If the Record Format field contains zero then the Record Attribute field shall be ignored in interchange.

This field shall be recorded according to 7.1.1.

9.5.10 Record Length (BP 81 to 84)

This field shall specify a 16-bit number as follows.

If the Record Format field contains the number O, the Record Length field shall contain zero.

If the Record Format field contains the number 1, the Record Length field shall specify the length in bytes of each record in the file.

If the Record Format field contains the number 2 or 3, the Record Length field shall specify the maximum length in bytes of a record in the file.

This field shall be recorded according to 7.2.3.

9.5.11 System Identifier (BP 85 to 116)

This field shall specify an identification of a system which can recognize and act upon the content of the System Use fields in the Extended Attribute Record and associated Directory Record.

The characters in this field shall be a-characters or a1-characters.

9.5.12 System Use (BP 117to 180)

This field shall be reserved for system use. Its content is not specified by this International Standard.

9.5.13 Extended Attribute Record Version (BP 181)

This field shall specify as an 8-bit number the version of the specification of the Extended Attribute Record.

1 shall indicate the structure of the present International Standard.

This field shall be recorded according to 7.1.1.

9.5.14 Length of Escape Sequences (BP 182)

This field shall specify as an 8-bit number the length in bytes of the Escape Sequences field in the Extended Attribute Record.

This field shall be recorded according to 7.1.1.

9.5.15 Reserved for future standardization (BP 183 to 246)

All bytes of this field shall be set to (OO).

9.5.16 Length of Application Use (BP 247 to 250)

This field shall specify as a 16-bit number the length in bytes of the Application Use field in the Extended Attribute Record.

This field shall be recorded according to 7.2.3.

9.5.17 Application Use [BP 251 to (250+LEN_AU)]

This field shall be reserved for application use. Its content is not specified by this International Standard.

9.5.18 Escape Sequences [BP (251+LEN_AU) to (250+LEN_ESC+LEN_AU)]

This field shall be optional. If present, this field shall contain escape sequences that designate the coded character set to be used to interpret the contents of the file. These escape sequences shall conform to ISO/IEC 2022, except that the ESCAPE character shall be omitted from each escape sequence.

The first or only escape sequence shall begin at the first byte of the field. Each successive escape sequence shall begin at the byte in the field immediately following the last byte of the preceding escape sequence. Any unused positions following the last escape sequence shall be set to (OO).

9.6 Consistency of File Attributes between Extended Attribute Records of a File

The following fields of the Extended Attribute Record associated with the File Sections of a file shall contain the same values:

• Record Format field;
• Record Attributes field;
• Record Length field, if the records are fixed-length records (see 6.10.3).

10 Levels of Interchange

This International Standard specifies three nested levels of interchange.

10.1 Level 1

At Level 1 the following restrictions shall apply to a volume identified by a Primary Volume Descriptor or by a Supplementary Volume Descriptor:

• each file shall consist of only one File section;
• a File Name shall not contain more than eight d-characters or eight d1-characters;
• a File Name Extension shall not contain more than three d-characters or three d1-characters;
• a Directory Identifier shall not contain more than eight d-characters or eight d1-characters.

At Level 1 the following restrictions shall apply to a volume identified by an Enhanced Volume Descriptor:

• each file shall consist of only one File Section.

10.2 Level 2

At Level 2 the following restrictions shall apply to a volume identified by a Primary Volume Descriptor, by a Supplementary Volume Descriptor or by an Enhanced Volume Descriptor:

• each file shall consist of only one File Section.

10.3 Level 3

At Level 3 no restrictions shall apply.