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One New Thing
Friday, February 13, 2004
One New Thing: Differences between writing to a CD-ROM using UDF and ISO 9660.

Now that CD/DVD burning is becoming more common in libraries I imagine many of us have experienced the charm of CDs that won’t burn, won’t read, or have data magically burnt onto them by processes you can’t fathom.

I personally have never been in favour of the option we see sometimes for making your CD work like a floppy: that is you can add and delete data instantly and without having to click a Record button. I don’t like it because I know it won’t read on everyone’s computers. So today I have endeavoured to find out why this is.

CD-ROMs in the past used a file format called ISO 9660 which was obviously an international standard. (There is also Joliet, which is basically the same thing except your filenames can be longer.) This is what you get when you add files to your CD then burn them on. Most computers and CD-ROM drives will read CDs in this format. What makes a CD act like a floppy is using the UDF file format which supports packet writing: basically writing data in little bits and pieces instead of big chunks. But then not every computer will read it, unless it is able to read UDF as well as ISO 9660. (Plus there are different versions of UDF too.) Seems like you can install UDF readers on a computer that can’t read a CD in UDF format. That could be a useful piece of information for any librarian faced with a client that can’t read the disc they burned in the library on their home computer…

And because it’s Friday, go laugh with the Warrior Librarian. My personal favourite from this site remains the OPAC Error Messages. :)

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