why do cdroms use the iso 9660 file system and not a file system like FAT or NTFS ?

The CD-ROM was originally intended to be a replacement for the old vinyl technology used to distribute music - records. This means that the CD-ROM works actually quite a lot like a record: It doesn't have sectors like magnetic computer storage like floppy disks or hard drives. The data on a CD-ROM is stored in a completely linear mode like on a record - you start writing in the middle and work yourself out in circles towards the outer parts of the disc; this is why reading from the last part of the disk is much faster than reading from the beginning - the rotation speed is much higher at the edges).

File systems for disk devices (and others) generally use sectors. Sectors are fractional parts of a track (which is a full circle around the platter). In hard drives and floppies you can easily jump between tracks and sectors but this is not the case with the CD-ROM because of its legacy - the CD-ROM read head follows the track (even though it can skip to other tracks) and is very slow to hop to other parts. Furthermore, when a CD is created it is "burned" in a linear way - it does not jump to one sector and write there, then jump to another to write another part of the file there like a hard drive running FAT/NTFS would do.

The ISO9660 file system was developed to make storing non-audio data on a CD and to make it easily accessible. It is an extremely simple file system, but it worked, and it still works sufficiently.


Håkan

thank you very very very very much, this was exactly the information i needed, thanks for the quick reply !!!