ISO 9660 is a standard issued by the International Organization for Standardization that describes the file system for CD-ROMs . Also known as CDFS ( Compact Disc File System ). The purpose of the standard is to ensure media compatibility under different operating systems , such as Unix , Mac OS , Windows .
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An extension of the standard, called Joliet , adds support for long file names and non- ASCII characters in names. Used on all media released after 1995 [1] .
A DVD can also use ISO 9660, but the UDF file system is more suitable for them, as it has support for large media and is better suited for modern operating systems.
BLU-RAY (BD) uses only the UDF file system.
Content
History
The standard was released in 1988 by a group of companies called High Sierra . It was later adopted as an ECMA-119 standard.
Specification
There are several levels of specification:
- Level 1 : File names are limited to eight characters and three extension characters. Names use only letters of the Latin alphabet. Fragmentation of files is not allowed, the file can be located only in a continuous chain of sectors. Directory names must be 8 characters or less. The maximum depth of nested directories is up to 8.
- Level 2 : File names are limited to 32 characters. The character set in the names is not limited.
- Level 3 : Files can be fragmented (this is necessary for batch or incremental burning of CDs).
Limitations
Restrictions on file and directory names
- You can use only uppercase letters, numbers, and the underscore.
- File names must not include spaces.
- File names must not begin or end with a period.
- File names must not have more than one dot.
- Directory names must not contain periods.
To remove some of the restrictions on file names in 1995, Microsoft proposed the Joliet extension, which has become widely used [2] .
Restriction on the depth of directory nesting
The maximum directory nesting depth is 8.
File Size Limit
The maximum file size in ISO 9660 is limited to 2 GB.
Directory Limit
Version Number
ISO 9660: 1999
ISO 9660: 1999 is the latest update to the ISO 9660 standard. It removes some of the restrictions introduced in the old version of the standard, for example, extends the maximum path length to 207 characters, removes the limit of a maximum of 8 directory nesting levels, and overrides the special meaning of the "." ( period) in file names.
Operating System Support
The file system is widely supported by operating systems. A number of operating systems define their own extensions to store additional metadata, however, backward compatibility is usually maintained and the data remains readable by other operating systems.
Extensions
- Joliet
- Rock ridge
- Amiga rock ridge
- El torito
- Apple ISO9660 Extensions
Notes
- β Chris Kaspersky. How to recover an unreadable CD? . citforum (2003). Date of treatment January 4, 2019.
- β Chris Kaspersky. How to recover an unreadable CD? . citforum (2003). Date of treatment January 4, 2019.
Literature
- ISO 9660: 1988 Information processing - Volume and file structure of CD-ROM for information interchange
- Standard ECMA-119. Volume and File Structure of CDROM for Information Interchange , 3rd edition (December 2017 )
Links
- The ISO 9660 File System , May 1995 - CD-ROM file system description
- ISO 9660 , OSDev Wiki
- Inside the ISO-9660 Filesystem Format , Dr. Dobbs, 1992
- IMAPI Disc Formats // Microsoft
- Introduction to ISO 9660, what it is, how it is implemented, and how it has been extended , 1993-1995