Since most UNIX+ filenames do not conform to this standard, any filenames that did not conform were translated to conform to the ISO standard before being stored on CD-ROM. And, where some of the directories were nested 8 or more levels deep, any directories that were too deep were moved up, until all directories and filenames on the disc conformed to the standard.
To allow a program (or a person) to recreate the original names, a translation file (normally called YMTRANS.TBL) is placed in each directory, giving, for every directory entry in that directory other than YMTRANS.TBL, the type of each entry, each entry's translated name, each entry's original UNIX+ name, and, if needed, the entry's symbolic link (for type L entries) or information about device node described by the entry. The current file types are :
F for ordinary files
D for ordinary directories
M for moved directories
L for symbolic links
B for block device nodes
C for character device nodes
P for pipe files
S for socket files
char type; /* valid values : F, D, M, L, B, C, P, or S */
char space; /* a space character (0x20) */
char trans_name [14]; /* the translated entry name */
char tab1; /* a tab character (0x09) */
char *orig_name; /* the original UNIX+ name. This is variable
length name is terminated by either a newline
character (0x0a) or a tab character (0x09),
which are not considered part of the field */
For type F, D, P, and S entries, this is followed by a :
char newline; /* a newline character (0x0a), ending the
entry */
For type M entries, this is followed by a :
char tab2; /* a tab character (0x09) */
char *moved_name; /* the relative path to the new location
of the directory. This variable length
name is terminated by a newline character
(0x0a), which is not considered part of
the field */
char newline; /* a newline character (0x0a), ending the
entry */
For type L entries, this is followed by a :
char tab2; /* a tab character (0x09) */
char *link_moved_name; /* the symbolic link value. This variable
length name is terminated by a newline
character (0x0a), which is not considered
part of the field */
char newline; /* a newline character (0x0a), ending the
entry */
For type B and C entries, this is followed by a :
char tab2; /* a tab character (0x09) */
char *major_number; /* the major device number for the file.
If the entry was created on an 88Open
compliant machine, it is listed as a '-'.
This variable length field is terminated by
a space character (0x20), which is not
considered part of the field */
char space2; /* a space character (0x20) */
char *minor_number; /* the minor device number for the file.
If the entry was created on an 88Open
compliant machine, it contains the entire
device number. This variable length field
is terminated by a newline character (0x0a),
which is not considered part of the field */
char newline; /* a newline character (0x0a), ending the
entry */
This discussion of the restrictions of the ISO 9660 standard assumes the most strict level of interchange mentioned by the standard, Interchange Level 1. While there are less restrictive levels of interchange (namely levels 2 and 3), Level 1 was chosen to allow compatibility with the CD-ROM drivers of other machines, such as the IBM PC. Further, changing to a more lenient form of interchange would only remove the primary and extension filename length restrictions and replace them with a maximum filename length of 31 characters, while still enforcing the upper case only character set and the 8 level deep directory tree restrictions. (See the ISO 9660 document for more details).
The current version of the cd_link program ignores the B, C, P, and S entries, as there is not yet a well defined, machine independent mapping for these entries.
+ UNIX is a trademark of Bell Laboratories.