ISO 9660 (also known as ECMA-119) is a

file system In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...

for

optical disc In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data (bits) in the form of pits and lands on a special material, often aluminum, on one of its flat surfaces. ...

media. Being sold by the

International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...

(ISO) the file system is considered an

international International is an adjective (also used as a noun) meaning "between nations". International may also refer to: Music Albums * ''International'' (Kevin Michael album), 2011 * ''International'' (New Order album), 2002 * ''International'' (The T ...

technical standard A technical standard is an established norm or requirement for a repeatable technical task which is applied to a common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and production methods, ...

. Since the specification is available for anybody to purchase, implementations have been written for many

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

s. ISO 9660 traces its roots to the ''High Sierra Format'', which arranged file information in a dense, sequential layout to minimize nonsequential access by using a hierarchical (eight levels of directories deep) tree file system arrangement, similar to UNIX and

FAT In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...

. To facilitate cross platform compatibility, it defined a minimal set of common file attributes (directory or ordinary file and time of recording) and name attributes (name, extension, and version), and used a separate system use area where future optional extensions for each file may be specified. High Sierra was adopted in December 1986 (with changes) as an international standard by

Ecma International Ecma International () is a nonprofit standards organization for information and communication systems. It acquired its current name in 1994, when the European Computer Manufacturers Association (ECMA) changed its name to reflect the organizatio ...

as ECMA-119 and submitted for fast tracking to the

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

, where it was eventually accepted as ISO 9660:1988. Subsequent amendments to the standard were published in 2013 and 2020. The first 16 sectors of the file system are empty and reserved for other uses. The rest begins with a ''volume descriptor set'' (a header block which describes the subsequent layout) and then the path tables, directories and files on the disc. An ISO 9660 compliant disc must contain at least one ''primary volume descriptor'' describing the file system and a ''volume descriptor set terminator'' which is a volume descriptor that marks the end of the descriptor set. The primary volume descriptor provides information about the volume, characteristics and metadata, including a root directory record that indicates in which sector the root directory is located. Other fields contain metadata such as the volume's name and creator, along with the size and number of logical blocks used by the file system. Path tables summarize the directory structure of the relevant directory hierarchy. For each directory in the image, the path table provides the directory identifier, the location of the extent in which the directory is recorded, the length of any extended attributes associated with the directory, and the index of its parent directory path table entry. There are several extensions to ISO 9660 that relax some of its limitations. Notable examples include ''Rock Ridge'' (Unix-style permissions and longer names), ''Joliet'' (

Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...

, allowing non-

Latin script The Latin script, also known as Roman script, is an alphabetic writing system based on the letters of the classical Latin alphabet, derived from a form of the Greek alphabet which was in use in the ancient Greek city of Cumae, in southern Italy ...

s to be used), ''El Torito'' (enables CDs to be

bootable In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some ...

) and the ''Apple ISO 9660 Extensions'' (file characteristics specific to the

classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...

and

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

, such as

resource fork The resource fork is a fork or section of a file on Apple's classic Mac OS operating system, which was also carried over to the modern macOS for compatibility, used to store structured data along with the unstructured data stored within the data f ...

s, file backup date and more).

History

Compact disc The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then rele ...

s were originally developed for recording musical data, but soon were used for storing additional digital data types because they were equally effective for archival mass data storage. Called

CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...

s, the lowest level format for these type of compact discs was defined in the '' Yellow Book'' specification in 1983. However, this book did not define any format for organizing data on CD-ROMs into logical units such as files, which led to every CD-ROM maker creating their own format. In order to develop a CD-ROM

standard (''Z39.60'' - ''Volume and File Structure of CDROM for Information Interchange''), the

National Information Standards Organization The National Information Standards Organization (NISO; ) is a United States non-profit standards organization that develops, maintains and publishes technical standards related to publishing, bibliographic and library applications. It was found ...

(NISO) set up Standards Committee SC EE (Compact Disc Data Format) in July 1985. In September/ October 1985 several companies invited experts to participate in the development of a working paper for such a standard. In November 1985, representatives of computer hardware manufacturers gathered at the

High Sierra Hotel and Casino Hard Rock Lake Tahoe (formerly Sahara Tahoe, High Sierra, Horizon Lake Tahoe and Park Tahoe) is a hotel and casino located in Stateline, Nevada. Also previously known as Sahara Tahoe and High Sierra resorts, it is one of four major casino hotels ...

(currently called the

Hard Rock Hotel and Casino Hard Rock Cafe, Inc. is a British-based multinational chain of theme restaurants, memorabilia shops, casinos and museums founded in 1971 by Isaac Tigrett and Peter Morton in London. In 1979, the cafe began covering its walls with rock and ro ...

) near

Lake Tahoe Lake Tahoe (; was, Dáʔaw, meaning "the lake") is a Fresh water, freshwater lake in the Sierra Nevada (U.S.), Sierra Nevada of the United States. Lying at , it straddles the state line between California and Nevada, west of Carson City, Nevad ...

, California. This group became known as the ''High Sierra Group'' (''HSG''). Present at the meeting were representatives from

Apple Computer Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...

AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile tel ...

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...

(DEC),

Hitachi () is a Japanese multinational corporation, multinational Conglomerate (company), conglomerate corporation headquartered in Chiyoda, Tokyo, Japan. It is the parent company of the Hitachi Group (''Hitachi Gurūpu'') and had formed part of the Ni ...

, LaserData,

Microware Microware Systems Corporation was an American software company based in Clive, Iowa, that produced the OS-9 real-time operating system. Microware Systems Corporation existed as a separate entity from 1977 until September 2001, when it was bought ...

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

, 3M,

Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...

, Reference Technology Inc.,

Sony Corporation , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...

, TMS Inc., VideoTools (later Meridian),

Xebec A xebec ( or ), also spelled zebec, was a Mediterranean sailing ship that was used mostly for trading. Xebecs had a long overhanging bowsprit and aft-set mizzen mast. The term can also refer to a small, fast vessel of the sixteenth to nineteenth ...

, and Yelick. The meeting report evolved from the ''Yellow Book'' CD-ROM standard, which was so open ended it was leading to diversification and creation of many incompatible data storage methods. The ''High Sierra Group Proposal'' (''HSGP'') was released in May 1986, defining a file system for CD-ROMs commonly known as the High Sierra Format. A draft version of this proposal was submitted to the

European Computer Manufacturers Association Ecma International () is a nonprofit standards organization for information and communication systems. It acquired its current name in 1994, when the European Computer Manufacturers Association (ECMA) changed its name to reflect the organization ...

(ECMA) for standardization. With some changes, this led to the issue of the initial edition of the ECMA-119 standard in December 1986. The ECMA submitted their standard to the

International Standards Organization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Art ...

(ISO) for ''fast tracking'', where it was further refined into the ISO 9660 standard. For compatibility the second edition of ECMA-119 was revised to be equivalent to ISO 9660 in December 1987.https://web.archive.org/web/20161118181416/http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-119.pdf -->
/ref> ''ISO 9660:1988'' was published in 1988. The main changes from the High Sierra Format in the ECMA-119 and ISO 9660 standards were international extensions to allow the format to work better on non-US markets. In order not to create incompatibilities, NISO suspended further work on Z39.60, which had been adopted by NISO members on 28 May 1987. It was withdrawn before final approval, in favour of ISO 9660. In 2013, ISO published Amendment 1 to the ISO 9660 standard, introducing new data structures and relaxed file name rules intended to "bring harmonization between ISO 9660 and widely used ' Joliet Specification'." In December 2017, a 3rd Edition of ECMA-119 was published that is technically identical with ISO 9660, Amendment 1. In 2020, ISO published Amendment 2, which adds some minor clarifying matter, but does not add or correct any technical information of the standard.

Specifications

The following is the rough overall structure of the ISO 9660 file system. Multi-byte values can be stored in three different formats:

little-endian In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most si ...

big-endian In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most sig ...

, and in a concatenation of both types in what the specification calls "both-byte" order. Both-byte order is required in several fields in the volume descriptors and directory records, while path tables can be either little-endian or big-endian.

Top level

The ''system area'', the first 32,768 data bytes of the disc (16 sectors of 2,048 bytes each), is unused by ISO 9660 and therefore available for other uses. While it is suggested that they are reserved for use by

bootable media A boot disk is a removable digital data storage medium from which a computer can load and run ( boot) an operating system or utility program. The computer must have a built-in program which will load and execute a program from a boot disk meeting ...

, a CD-ROM may contain an alternative file system descriptor in this area, and it is often used by

hybrid CD A hybrid disc is a disc, such as CD-ROM or Blu-ray, which contains multiple types of data which can be used differently on different devices. These include CD-ROM music albums containing video files viewable on a personal computer, or feature fil ...

s to offer

-specific and

-specific content.

Volume descriptor set

The ''data area'' begins with the ''volume descriptor set'', a set of one or more ''volume descriptors'' terminated with a ''volume descriptor set terminator''. These collectively act as a header for the data area, describing its content (similar to the BIOS parameter block used by

, HPFS and

NTFS New Technology File System (NTFS) is a proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) as the preferred fil ...

formatted disks). Each volume descriptor is 2048 bytes in size, fitting perfectly into a single Mode 1 or Mode 2 Form 1 sector. They have the following structure: The data field of a volume descriptor may be subdivided into several fields, with the exact content depending on the type. Redundant copies of each volume descriptor can also be included in case the first copy of the descriptor becomes corrupt. Standard volume descriptor types are the following: An ISO 9660 compliant disc must contain at least one ''primary volume descriptor'' describing the file system and a ''volume descriptor set terminator'' for indicating the end of the descriptor sequence. The ''volume descriptor set terminator'' is simply a particular type of volume descriptor with the purpose of marking the end of this set of structures. The primary volume descriptor provides information about the volume, characteristics and metadata, including a root directory record that indicates in which sector the root directory is located. Other fields contain the description or name of the volume, and information about who created it and with which application. The size of the logical blocks which the file system uses to segment the volume is also stored in a field inside the primary volume descriptor, as well as the amount of space occupied by the volume (measured in number of logical blocks). In addition to the primary volume descriptor(s), ''supplementary volume descriptors'' or ''enhanced volume descriptors'' may be present. Supplementary volume descriptors describe the same volume as the primary volume descriptor does, and are normally used for providing additional code page support when the standard code tables are insufficient. The standard specifies that

ISO 2022 ISO/IEC 2022 ''Information technology—Character code structure and extension techniques'', is an ISO/ IEC standard (equivalent to the ECMA standard ECMA-35, the ANSI standard ANSI X3.41 and the Japanese Industrial Standard JIS X 0202) in the ...

is used for managing code sets that are wider than 8 bytes, and that ISO 2375 escape sequences are used to identify each particular code page used. Consequently, ISO 9660 supports international single-byte and multi-byte character sets, provided they fit into the framework of the referenced standards. However, ISO 9660 does not specify any code pages that are guaranteed to be supported: all use of code tables other than those defined in the standard itself are subject to agreement between the originator and the recipient of the volume. Enhanced volume descriptors were introduced in ISO 9660, Amendment 1. They relax some of the requirements of the other volume descriptors and the directory records referenced by them: for example, the directory depth can exceed eight, file identifiers need not contain '.' or file version number, the length of a file and directory identifier is maximized to 207.

Path tables

Path tables summarize the directory structure of the relevant directory hierarchy. For each directory in the image, the path table provides the directory identifier, the location of the extent in which the directory is recorded, the length of any extended attributes associated with the directory, and the index of its parent directory path table entry. The parent directory number is a 16-bit number, limiting its range from 1 to 65,535.

Directories and files

Directory entries are stored following the location of the root directory entry, where evaluation of filenames is begun. Both directories and files are stored as

extents In computing, an extent is a contiguous area of storage reserved for a file in a file system, represented as a range of block numbers, or tracks on count key data devices. A file can consist of zero or more extents; one file fragment requires on ...

, which are sequential series of sectors. Files and directories are differentiated only by a file attribute that indicates its nature (similar to

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...

). The attributes of a file are stored in the directory entry that describes the file, and optionally in the extended attribute record. To locate a file, the directory names in the file's path can be checked sequentially, going to the location of each directory to obtain the location of the subsequent subdirectory. However, a file can also be located through the path table provided by the file system. This path table stores information about each directory, its parent, and its location on disc. Since the path table is stored in a contiguous region, it can be searched much faster than jumping to the particular locations of each directory in the file's path, thus reducing seek time. The standard specifies three nested levels of interchange (paraphrased from section 10): * Level 1: File names are limited to eight characters with a three-character extension. Directory names are limited to eight characters. Files may contain one single file section. * Level 2: Files may contain one single file section. * Level 3: No additional restrictions than those stipulated in the main body of the standard. That is, directory identifiers may not exceed 31 characters in length, and file name + '.' + file name extension may not exceed 30 characters in length (sections 7.5 and 7.6). Files are also allowed to consist of multiple non-contiguous sections (with some restrictions as to order). Additional restrictions in the body of the standard: The depth of the directory hierarchy must not exceed 8 (root directory being at level 1), and the path length of any file must not exceed 255. (section 6.8.2.1). The standard also specifies the following name restrictions (sections 7.5 and 7.6): * All levels restrict file names in the mandatory file hierarchy to upper case letters, digits, underscores ("_"), and a dot. (See also section 7.4.4 and Annex A.) * 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. * File names shall not have more than one dot. * Directory names shall not use dots at all. A CD-ROM producer may choose one of the lower Levels of Interchange specified in chapter 10 of the standard, and further restrict file name length from 30 characters to only 8+3 in file identifiers, and 8 in directory identifiers in order to promote interchangeability with implementations that do not implement the full standard. All numbers in ISO 9660 file systems except the single byte value used for the GMT offset are unsigned numbers. As the length of a file's extent on disc is stored in a 32 bit value, it allows for a maximum length of just over 4.2 GB (more precisely, one byte less than 4

GiB The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...

). It is possible to circumvent this limitation by using the multi-extent (fragmentation) feature of ISO 9660 Level 3 to create ISO 9660 file systems and single files up to 8 TB. With this, files larger than 4 GiB can be split up into multiple extents (sequential series of sectors), each not exceeding the 4 GiB limit. For example, the free software such as

InfraRecorder InfraRecorder is an open-source CD and DVD writing program for Microsoft Windows. First started by Christian Kindahl in the Google Summer of Code 2006, InfraRecorder uses the cdrtools software library to perform the actual burning. Since 0.4 ...

ImgBurn ImgBurn is an optical disc authoring program that allows the recording of many types of CD, DVD and Blu-ray images to recordable media (.cue files are supported as of version 2.4.0.0). Starting with version 2.0.0.0, ImgBurn can also burn files a ...

and

mkisofs cdrtools (formerly known as cdrecord) is a collection of independent projects of free software/open source computer programs. The project was maintained for over two decades by Jörg Schilling, who died on October 10, 2021. Because of some ...

as well as

Roxio Toast Roxio Toast is an optical disc authoring and media conversion software application for Mac OS X. Its name is a play on the word ''burn'', a term used for the writing of information onto a disc through the use of a laser. Discs can be burned di ...

are able to create ISO 9660 file systems that use multi-extent files to store files larger than 4 GiB on appropriate media such as recordable DVDs.

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

supports multiple extents.

Extensions and improvements

There are several extensions to ISO 9660 that relax some of its limitations. Notable examples include ''Rock Ridge'' (Unix-style permissions and longer names), ''Joliet'' (

, allowing non-

s to be used), ''El Torito'' (enables CDs to be

) and the ''Apple ISO 9660 Extensions'' (file characteristics specific to the

and

, such as

s, file backup date and more).

SUSP

''System Use Sharing Protocol'' (SUSP,

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...

P1281) provides a generic way of including additional properties for any directory entry reachable from the primary volume descriptor (PVD). In an ISO 9660 volume, every directory entry has an optional ''system use area'' whose contents are undefined and left to be interpreted by the system. SUSP defines a method to subdivide that area into multiple system use fields, each identified by a two-character signature tag. The idea behind SUSP was that it would enable any number of independent extensions to ISO 9660 to be created and included on a volume without conflicting. It also allows for the inclusion of property data that would otherwise be too large to fit within the limits of the system use area. SUSP defines several common tags and system use fields: * CE: Continuation area * PD: Padding field * SP: System use sharing protocol indicator * ST: System use sharing protocol terminator * ER: Extensions reference * ES: Extension selector Other known SUSP fields include: * AA: Apple extension, preferred * BA: Apple extension, old (length attribute is missing) * AS: Amiga file properties * ZF: zisofs compressed file, usually produced by program mkzftree or by libisofs. Transparently decompressed by Linux kernel if built with CONFIG_ZISOFS. * AL: records

Extended File Attributes Extended file attributes are file system features that enable users to associate computer files with metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem (such as permissions or re ...

, including ACLs. Proposed by

libburnia Libburnia is a project that develops a collection of libraries and command-line tools for burning CDs, DVDs and Blu-ray media. Project overview Libburnia is the name of a project to develop various pieces of disk recording software. * libisofs ...

, supported by libisofs. The Apple extensions do not technically follow the SUSP standard; however the basic structure of the AA and AB fields defined by Apple are

forward compatible Forward compatibility or upward compatibility is a design characteristic that allows a system to accept input intended for a later version of itself. The concept can be applied to entire systems, electrical interface Interface or interfacing may ...

with SUSP; so that, with care, a volume can use both Apple extensions as well as RRIP extensions.

Rock Ridge

The ''Rock Ridge Interchange Protocol'' (RRIP,

P1282) is an extension which adds

POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...

semantics. The availability of these extension properties allows for better integration with

and

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating systems. The standard takes its name from the fictional town ''Rock Ridge'' in

Mel Brooks Mel Brooks (born Melvin James Kaminsky; June 28, 1926) is an American actor, comedian and filmmaker. With a career spanning over seven decades, he is known as a writer and director of a variety of successful broad farces and parodies. He began h ...

' film '' Blazing Saddles''. The RRIP extensions are, briefly: * Longer file names (up to 255 bytes) and fewer restrictions on allowed characters (support for lowercase, etc.) * UNIX-style file modes,

user id Unix-like operating systems identify a user by a value called a user identifier, often abbreviated to user ID or UID. The UID, along with the group identifier (GID) and other access control criteria, is used to determine which system resources a us ...

s and group ids, and file

timestamp A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolut ...

s * Support for

Symbolic link In computing, a symbolic link (also symlink or soft link) is a file whose purpose is to point to a file or directory (called the "target") by specifying a path thereto. Symbolic links are supported by POSIX and by most Unix-like operating system ...

s and device files * Deeper directory hierarchy (more than 8 levels) * Efficient storage of

sparse file In computer science, a sparse file is a type of computer file that attempts to use file system space more efficiently when the file itself is partially empty. This is achieved by writing brief information (metadata) ''representing'' the empty block ...

s The RRIP extensions are built upon SUSP, defining additional tags for support of POSIX semantics, along with the format and meaning of the corresponding system use fields: * RR: Rock Ridge extensions in-use indicator (note: dropped from standard after version 1.09) * PX: POSIX file attributes * PN: POSIX device numbers * SL: symbolic link * NM: alternate name * CL: child link * PL: parent link * RE: relocated directory * TF: time stamp * SF: sparse file data ''Amiga Rock Ridge'' is similar to RRIP, except it provides additional properties used by

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early version ...

. It too is built on the SUSP standard by defining an "AS"-tagged system use field. Thus both Amiga Rock Ridge and the POSIX RRIP may be used simultaneously on the same volume. Some of the specific properties supported by this extension are the additional

Amiga Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...

-bits for files. There is support for attribute "P" that stands for "pure" bit (indicating re-entrant command) and attribute "S" for script bit (indicating

batch file Batch may refer to: Food and drink * Batch (alcohol), an alcoholic fruit beverage * Batch loaf, a type of bread popular in Ireland * A dialect term for a bread roll used in North Warwickshire, Nuneaton and Coventry, as well as on the Wirral ...

). This includes the protection flags plus an optional comment field. These extensions were introduced by Angela Schmidt with the help of Andrew Young, the primary author of the Rock Ridge Interchange Protocol and System Use Sharing Protocol. The first publicly available software to master a CD-ROM with Amiga extensions was MakeCD, an Amiga software which Angela Schmidt developed together with Patrick Ohly.

El Torito

''El Torito'' is an extension designed to allow

booting In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so som ...

a computer from a CD-ROM. It was announced in November 1994 and first issued in January 1995 as a joint proposal by IBM and BIOS manufacturer

Phoenix Technologies Phoenix Technologies Ltd is an American company that designs, develops and supports core system software for personal computers and other computing devices. The company's products commonly referred to as BIOS (Basic Input/Output System) or fir ...

. According to legend, the El Torito CD/DVD extension to ISO 9660 got its name because its design originated in an

El Torito El Torito (Spanish for "the little bull") is an American chain that serves Mexican food. El Torito operates 69 restaurants primarily in California.Irvine, California Irvine () is a Planned community, master-planned city in South Orange County, California, United States, in the Los Angeles metropolitan area. The Irvine Company started developing the area in the 1960s and the city was formally incorporated on ...

(). The initial two authors were Curtis Stevens, of Phoenix Technologies, and Stan Merkin, of IBM. A 32-bit PC BIOS will search for boot code on an ISO 9660 CD-ROM. The standard allows for booting in two different modes. Either in hard disk emulation when the boot information can be accessed directly from the CD media, or in floppy emulation mode where the boot information is stored in an

image file An Image file format is a file format for a digital image. There are many formats that can be used, such as JPEG, PNG, and GIF. Most formats up until 2022 were for storing 2D images, not 3D ones. The data stored in an image file format may be ...

of a

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...

, which is loaded from the CD and then behaves as a virtual floppy disk. This is useful for computers that were designed to boot only from a floppy drive. For modern computers the "no emulation" mode is generally the more reliable method. The BIOS will assign a BIOS drive number to the CD drive. The drive number (for

INT 13H INT 13h is shorthand for BIOS interrupt call 13 hex, the 20th interrupt vector in an x86-based (IBM PC-descended) computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides sector-based hard disk and ...

) assigned is any of 80_hex (

hard disk A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...

emulation), 00_hex (

emulation) or an arbitrary number if the BIOS should not provide emulation. Emulation is useful for booting older

s from a CD, by making it appear to them as if they were booted from a hard or floppy disk. El Torito can also be used to produce CDs which can boot up

operating systems, by including the

GRUB Grub can refer to Grub (larva), of the beetle superfamily Scarabaeoidea, or as a slang term for food. It can also refer to: Places * Grub, Appenzell Ausserrhoden, Switzerland * Grub, St. Gallen, Switzerland * Grub (Amerang), a hamlet in Bavaria, ...

bootloader on the CD and following the Multiboot Specification. While the El Torito spec alludes to a "Mac" platform ID, PowerPC-based Apple Macintosh computers don't use it.

Joliet

''Joliet'' is an extension specified and endorsed by

and has been supported by all versions of its

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

since

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturin ...

and

Windows NT 4.0 Windows NT 4.0 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It is the direct successor to Windows NT 3.51, which was released to manufacturing on July 31, 1996, and then to retail ...

. Its primary focus is the relaxation of the filename restrictions inherent with full ISO 9660 compliance. Joliet accomplishes this by supplying an additional set of filenames that are encoded in

UCS-2 The Universal Coded Character Set (UCS, Unicode) is a standard set of characters defined by the international standard ISO/IEC 10646, ''Information technology — Universal Coded Character Set (UCS)'' (plus amendments to that standard), whi ...

BE (

UTF-16 UTF-16 (16-bit computing, 16-bit Unicode Transformation Format) is a character encoding capable of encoding all 1,112,064 valid code points of Unicode (in fact this number of code points is dictated by the design of UTF-16). The encoding is variab ...

BE in practice since Windows 2000). These filenames are stored in a special supplementary volume descriptor, that is safely ignored by ISO 9660-compliant software, thus preserving backward compatibility. The specification only allows filenames to be up to 64

characters in length. However, the documentation for

states filenames up to 103 characters in length do not appear to cause problems. Microsoft has documented it "can use up to 110 characters." Joliet allows Unicode characters to be used for all text fields, which includes file names and the volume name. A "Secondary" volume descriptor with type 2 contains the same information as the Primary one (sector 16 offset 40 bytes), but in UCS-2BE in sector 17, offset 40 bytes. As a result of this, the volume name is limited to 16 characters. Many current PC operating systems are able to read Joliet-formatted media, thus allowing exchange of files between those operating systems even if non-Roman characters are involved (such as Arabic, Japanese or Cyrillic), which was formerly not possible with plain ISO 9660-formatted media. Operating systems which can read Joliet media include: *

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

; Microsoft recommends the use of the Joliet extension for developers targeting Windows. *

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

OpenSolaris OpenSolaris () is a discontinued open-source computer operating system based on Solaris and created by Sun Microsystems. It was also, perhaps confusingly, the name of a project initiated by Sun to build a developer and user community around th ...

Haiku is a type of short form poetry originally from Japan. Traditional Japanese haiku consist of three phrases that contain a ''kireji'', or "cutting word", 17 '' on'' (phonetic units similar to syllables) in a 5, 7, 5 pattern, and a ''kigo'', or se ...

RISC OS RISC OS is a computer operating system originally designed by Acorn Computers Ltd in Cambridge, England. First released in 1987, it was designed to run on the ARM chipset, which Acorn had designed concurrently for use in its new line of Archim ...

Romeo

''Romeo'' was developed by

Adaptec Adaptec was a computer storage company and remains a brand for computer storage products. The company was an independent firm from 1981 to 2010, at which point it was acquired by PMC-Sierra, which itself was later acquired by Microsemi, which itse ...

and allows the use of long filenames up to 128 characters. However, Romeo is not backwards compatible with ISO 9660 and discs authored using this file system can only be read under the Windows 9x and

Windows NT Windows NT is a proprietary graphical operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems sc ...

platforms, thus not allowing exchange of files between those operating systems if non-Roman characters are involved (such as Arabic, Japanese or Cyrillic), for example ü becomes ³.

Apple extensions

authored a set of extensions that add

ProDOS ProDOS is the name of two similar operating systems for the Apple II series of personal computers. The original ProDOS, renamed ProDOS 8 in version 1.2, is the last official operating system usable by all 8-bit Apple II series computers, and w ...

or HFS/HFS+ (the primary contemporary file system for Mac OS) properties to the filesystem. Some of the additional metadata properties include: * Date of last backup * File type * Creator code * Flags and data for display * Reference to a

In order to allow non-Macintosh systems to access Macintosh files on CD-ROMs, Apple chose to use an extension of the standard ISO 9660 format. Most of the data, other than the Apple specific metadata, remains visible to

s that are able to read ISO 9660.

Other extensions

For operating systems which do not support any extensions, a name translation file TRANS.TBL must be used. The TRANS.TBL file is a plain

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...

text file. Each line contains three fields, separated by an arbitrary amount of whitespace: * The file type ("F" for file or "D" for directory); * The ISO 9660 filename (including the usually hidden ";1" for files); and * The extended filename, which may contain spaces. Most implementations that create TRANS.TBL files put a single space between the file type and ISO 9660 name and some arbitrary number of tabs between the ISO 9660 filename and the extended filename. Native support for using TRANS.TBL still exists in many ISO 9660 implementations, particularly those related to

. However, it has long since been superseded by other extensions, and modern utilities that create ISO 9660 images either cannot create TRANS.TBL files at all, or no longer create them unless explicitly requested by the user. Since a TRANS.TBL file has no special identification other than its name, it can also be created separately and included in the directory before filesystem creation. The

ISO 13490 ISO/IEC 13490 (also known as Ecma International, ECMA-168) is the successor to ISO 9660 (level 3), intended to describe the file system of a CD-ROM or CD-R. ISO 13490 has several improvements over its predecessor. It fully addresses the filename ...

standard is an extension to the ISO 9660 format that adds support for multiple sessions on a disc. Since ISO 9660 is by design a read-only, pre-mastered file system, all the data has to be written in one go or "session" to the medium. Once written, there is no provision for altering the stored content. ISO 13490 was created to allow adding more files to a writeable disc such as

CD-R CD-R (Compact disc-recordable) is a digital optical disc storage format. A CD-R disc is a compact disc that can be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the in ...

in multiple sessions. JIS X 0606:1998, also known as ISO 9660:1999, is a Japanese Industrial Standard draft created by the Japanese National Body (JTC1 N4222) in order to make some improvements and remove some limitations from the original ISO 9660 standard. This draft was submitted in 1998, but it has not been ratified as an ISO standard yet. Some of its changes includes the removal of some restrictions imposed by the original standard by extending the maximum file name length to 207 characters, removing the eight-level maximum directory nesting limit, and removing the special meaning of the dot character in filenames. Some operating systems allow these relaxations as well when reading optical discs. Several disc authoring tools (such as

Nero Burning ROM Nero Burning ROM, commonly called Nero, is an optical disc authoring program from Nero AG. The software is part of the Nero Multimedia Suite but is also available as a stand-alone product. It is used for burning and copying optical discs such as ...

and

) support a so-called "ISO 9660:1999" mode (sometimes called "ISO 9660 v2" or "ISO 9660 Level 4" mode) that removes restrictions following the guidelines in the ISO 9660:1999 draft. The ISO 13346/ECMA-167 standard was designed in conjunction to the ISO 13490 standard. This new format addresses most of the shortcomings of ISO 9660, and a subset of it evolved into the

Universal Disk Format Universal Disk Format (UDF) is an open, vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design, ...

(UDF), which was adopted for

DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...

s. The volume descriptor table retains the ISO9660 layout, but the identifier has been updated.

Disc images

Optical disc image An optical disc image (or ISO image, from the ISO 9660 file system used with CD-ROM media) is a disk image that contains everything that would be written to an optical disc, disk sector by disc sector, including the optical disc file system. ...

s are a common way to electronically transfer the contents of CD-ROMs. They often have the

filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

.iso (.iso9660 is less common, but also in use) and are commonly referred to as "ISOs".

Platforms

Most operating systems support reading of ISO 9660 formatted discs, and most new versions support the extensions such as Rock Ridge and Joliet. Operating systems that do not support the extensions usually show the basic (non-extended) features of a plain ISO 9660 disc. Operating systems that support ISO 9660 and its extensions include the following: *

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

: access with extensions, such as MSCDEX.EXE (Microsoft CDROM Extension), NWCDEX.EXE or CORELCDX.EXE * Microsoft

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...

Windows ME Windows Millennium Edition, or Windows Me (marketed with the pronunciation of the pronoun "me"), is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It is the successor to Windo ...

: can read ISO 9660 Level 1, 2, 3, and Joliet * Microsoft

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RTM), releas ...

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...

, and newer Windows versions, can read ISO 9660 Level 1, 2, 3, Joliet, and ISO 9660:1999.

Windows 7 Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009. It is the successor to Windows Vista, released nearly ...

may also mistake UDF format for CDFS. for more information see UDF. *

and

BSD The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...

: ISO 9660 Level 1, 2, 3, Joliet,

Rock Ridge ISO 9660 (also known as ECMA-119) is a file system for optical disc media. Being sold by the International Organization for Standardization (ISO) the file system is considered an international technical standard. Since the specification is av ...

, and ISO 9660:1999 *

Apple GS/OS GS/OS is an operating system developed by Apple Computer for its Apple IIGS personal computer. It provides facilities for accessing the file system, controlling input/output devices, loading and running program files, and a system allowing progr ...

: ISO Level 1 and 2 support via the HS.FST File System Translator. *

Classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...

7 to 9: ISO Level 1, 2. Optional free software supports

and Joliet (including ISO Level 3)
Joke Ridge
an
Joliet Volume Access
*

(all versions): ISO Level 1, 2, Joliet and

Extensions. Level 3 is not currently supported, although users have been able to mount these discs *

supports the "AS" extensions (which preserve the Amiga protection bits and file comments) *

QNX QNX ( or ) is a commercial Unix-like real-time operating system, aimed primarily at the embedded systems market. QNX was one of the first commercially successful microkernel operating systems. The product was originally developed in the early ...

ULTRIX Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations. History The initial development of Unix occurred on DEC equip ...

OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...

eComStation eComStation or eCS is an operating system based on OS/2 Warp for the 32-bit x86 architecture. It was originally developed by Serenity Systems and Mensys BV under license from IBM. It includes additional applications, and support for new hard ...

and

ArcaOS ArcaOS is an operating system based on OS/2, developed and marketed by Arca Noae, LLC under license from IBM. It was codenamed Blue Lion during its development. It builds on OS/2 Warp 4.52 by adding support for new hardware, fixing defects and l ...

BeOS BeOS is an operating system for personal computers first developed by Be Inc. in 1990. It was first written to run on BeBox hardware. BeOS was positioned as a multimedia platform that could be used by a substantial population of desktop users a ...

Zeta Zeta (, ; uppercase Ζ, lowercase ζ; grc, ζῆτα, el, ζήτα, label= Demotic Greek, classical or ''zē̂ta''; ''zíta'') is the sixth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 7. It was derived f ...

and

OpenVMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...

supports only ISO 9660 Interchange levels 1–3, with ''no'' extensions *

support for optical media written on a PC is patchy. Most CD-Rs/RWs work perfectly, however DVD+-Rs/RWs/RAMs are entirely hit and miss running RISC OS 4.02, RISC OS 4.39 and RISC OS 6.20

References

External links

* * This is the ECMA release of the ISO 9660:1988 standard, available as a free download * * * * * * * *
ISOLINUX source code
(see isolinux.asm line 294 onward) * (see int 13h in interrupt.b, esp. functions 4a to 4d) * , discusses shortcomings of the standard
US Patent 5758352 - Common name space for long and short filenames
* {{ISO standards Amiga APIs Apple Inc. file systems Compact disc Disk file systems Ecma standards ISO standards, #09660 Optical computer storage Optical disc authoring Windows disk file systems