NSR and UDF specify platform-independent file systems. UDF is a subset of NSR. NSR stands for Non-Sequential Recording, and UDF for Universal Disk Format.
They allow disks created on a wide variety of operating systems to be interchangeable between different OSes. Think of NSR and UDF as similar to the way the ISO 9660 standard allows any type of computer with a CD-ROM drive to read the files from a CD-ROM disc. With NSR or UDF support, it would be possible to read and write to NSR-formatted MO disks from a Macintosh, PC, Amiga, and other types of computer.
NSR is covered by ISO standard 13346 and an equivalent ECMA standard, ECMA-167 2nd edition. NSR is the international standard logical disk format. It is not restricted to optical disks.
ISO standards documents are not available free of charge. Information about ordering them can be found on the ISO web site at:
ECMA (European Computer Manufacturers Association) standards documents are available free of charge. They can be downloaded in PDF and Microsoft Word formats from the ECMA web site, where you can also order a free CD-ROM containing all ECMA standards. The URL is:
UDF is a subset of NSR which is defined by the Optical Storage Technology Association (OSTA). You may have heard it mentioned in confunction with CD-RW and DVD technologies. It is likely to be more commonly used as the standard interchange format for MO disks. UDF specifications are available in PDF format from the OSTA web site, at:
If the Amiga is ever to support new technologies like CD-RW and DVD properly, an NSR or UDF filesystem needs to be written. The issue of NSR/UDF support is not only applicable to MO disks.