Universal Disk Format (UDF), which is compliant with ISO standard 13346, is the replacement format for ISO 9660, which is the current widely used format for CDRom disks. The problem with the ISO 9660 format is that file names are limited to the same limitations as filenames under MS-DOS, which is 8 characters of a filename plus a 3 character extension. Both modern versions of Microsoft Windows as well as Unix systems support long file names, but up until UDF, there has not been a platform common format for CDRom that would support long filenames.

What is interesting is that the development of UDF was not initiated to fix the limitations of ISO 9660, but was initiated to support DVD Rom. One of the other problems of ISO 9660 is that it does not address the ability to add more material to CDRoms. While this was the case when CDRoms where first introduced, the introduction of CD-Rs and CR-RWs made it possible to create a CDRom with some data, and then add more data later on.

When you read about compliance with the UDF standard, you will see references to UDF 1.02 and UDF 1.5. Support for UDF 1.02 is only supposed to cover DVD drives, whereas there should be support for UDF 1.5 with old CDRom drives. Most new CDRom drives should be able to handle UDF 1.5, CDRs, and CDRWs. However, there might not be support in the operating system for UDF. I found that I could read some UDF CDRWs with Windows 98, but could not read the same disks with Windows 2000. After applying the UDF reader from Adaptec, I was able to read the disks on Windows 95, 98, NT, and 2000.