Joliet (file system)
Encyclopedia
Joliet is the name of an extension to the ISO 9660
file system
. It has been specified and endorsed by Microsoft
and has been supported by all versions of its Windows
OS
since Windows 95
and Windows NT
. 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 to be encoded in UCS-2. These filenames are stored in a special supplementary header that is safely ignored by ISO 9660-compliant software, thus preserving backward compatibility.
The specification only allows filenames to be up to 64 Unicode
characters in length. However, filenames up to 103 characters in length do not appear to cause any problems.
Many current PC operating systems—including Microsoft Windows
, Linux
, Mac OS X
, FreeBSD
, and OpenSolaris
—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.
The Joliet extension is favored in the MS Windows world. It 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-2 in sector 17, offset 40 bytes. As a result of this, the volume name is limited to 16 characters.
The 'disktype' program prints the Unicode volume name from the Joliet volume descriptor if present.
ISO 9660
ISO 9660, also referred to as CDFS by some hardware and software providers, is a file system standard published by the International Organization for Standardization for optical disc media....
file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
. It has been specified and endorsed by Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
and has been supported by all versions of its Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
OS
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
since Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...
and Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
. 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 to be encoded in UCS-2. These filenames are stored in a special supplementary header that is safely ignored by ISO 9660-compliant software, thus preserving backward compatibility.
The specification only allows filenames to be up to 64 Unicode
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
characters in length. However, filenames up to 103 characters in length do not appear to cause any problems.
Many current PC operating systems—including Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, and OpenSolaris
OpenSolaris
OpenSolaris was an open source computer operating system based on Solaris created by Sun Microsystems. It was also the name of the project initiated by Sun to build a developer and user community around the software...
—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.
The Joliet extension is favored in the MS Windows world. It 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-2 in sector 17, offset 40 bytes. As a result of this, the volume name is limited to 16 characters.
The 'disktype' program prints the Unicode volume name from the Joliet volume descriptor if present.