A Guide to Data Recovery: UDF Reader: History

CD-ROMs (those are the silvery kind that retail software is stored on, not the recordable kind) almost always store their data in a format known as ISO 9660. As with most statements about CD-ROM formats, that was an oversimplification. The term "ISO 9660" is a specification that offers three different "levels" the CD-ROM might choose to be compatible with. And, multiple extensions to the standard popped up before long.

When recordable CDs for PCs arrived (first the record-once CD-R, and later the record-many-times CD-RW), people immediately wanted to use them for backup devices, and use them "like a floppy". That means, they wanted to copy some files to the recordable CD, and still be able to later add a few files to the same recordable CD. The traditional way to burn a recordable CD was to create a hard disk "image" of exactly what the recordable CD should contain, and then copy that into the CD in one big, unalterable burn.

Unfortunately, the form of ISO 9660 that most operating systems supported (including Windows) was not the best suited for the task of being able to incrementally add data over time. Vendors who wanted to offer the ability to add data to a recordable CD incrementally (also known as "packet writing") typically opted for a data format standard called "UDF". Some flavors of UDF could be fairly compatible with ISO 9660, and some flavors were clearly not compatible. As long as you read the recordable CD on the same computer and with the same software you used to burn it, everything was fine. It might not be readable by another computer using different CD software (or even a different version of the same software!).

Although Windows has been able to read read-only flavors of UDF since Windows 98 and Windows 2000, Windows still does not have any built-in support for the rewritable flavors of UDF. Microsoft says that will come in their next big release of Windows. In the meantime, reading some types of recordable CD that were created with third-party software will require, well, third-party software for you to read it from your Windows machine.

Do You Need a UDF Reader?UDF Reader