In ISO 9660 directory entry format there is no limit to number of entries. However, the maximum depth of directory nesting should not be more than eight.
Format of ISO 9660 directory entry is given below:
1) L is the length of the directory. It has a size of 1 byte.
2) E is the length of extended attributes. It has a size of 1 byte.
3) LF represents the location of file. It has a size of 8 bytes.
4) FS represents the file size. It has a size of 8 bytes.
5) DT represents date and time when CD-ROM was recorded. It has separate bytes for year, month, day, hour, minute, second, and time zone. It has a size of 7 bytes.
6) F represents the flag field which is used for miscellaneous bits. It has a size of 1 byte.
7) I represents the interleave field. It has a size of 2 bytes.
8) CD represents to which CD-ROM is the file is located. It has a size of 4 bytes.
9) S represents size of the file name. It has a size of 1 byte.
10) FN represents file name. File name has base name, a dot, an extension, a semicolon, and a binary version number. Following characters are allowed for base name and extension: upper case letters, digits 0-9, and underscore. Only these characters are used to make sure that a file name is readable in every computer. It has a size of 15 bytes.
11) P represents the padding field. It is used for forcing a directory entry to be an even number of bytes. It has a size of 0 bytes.
12) SU represents system use field. Size and function of a system use field is not defined. Usage depends on the operating system.