Richard Fangnail said:
One reason why I was confused was that when I copied files to a
floppy, it would be as simple and obvious as copying from one folder
to another within the same drive. But with CDROMs it's not quite as
obvious.
Have you found that when copying files to a CDROM, it writes to the
CDROM right away? I remember incidents where nothing was written
until I Ejected, at which point it wrote to it.
I think the problem here is a lack of understanding about the differences
between the media and how they store data. A floppy disk (and indeed a hard
disk) stores any files written to it as individual files spread over the
individual sectors of the disk (but actually grouped into clusters for
convenience). Thus it is possible to write one file and then sometime
later, write another file because the clusters are all individually
identifiable, findable and writeable.
CDs don't work that way. The read/write laser in a CD drive cannot
accurately locate precise locations on the disk. Consequently, all the
files written have to be assembled into a continuous stream and written as a
single track. Originally, you only had one go at writing this track. Once
written nothing could be added to it. Subsequent developments have allowed
CDs to be written in more than one 'session', but the actual number of
sessions is severely limited by several factors. The CD is provided with a
table of Contents and file allocation table that allows the files to be
located and read.
Now if you are using XPs own CD writing utility, you can drag and drop files
to the CD drive, but this doesn't actually write the file. You can continue
dragging and dropping files to assemble what you wish to burn to the CD.
Once you have finished, you click 'Write files to CD' and XP then assembles
the files, creates the supporting file structure for the CD and then writes
the whole lot to the CD in one go.
Most CD burning packages such Nero and Easy Media Creator perform much the
same job but with a bit more versatility (and they support DVD writing which
XP does not).
If you really want to write individual files to a CD in a similar manner to
floppy disk, there is software that supports such use. InCD from Nero and
Drag-to-Disk from Roxio are good examples (the former only supports CD-RW
disks). However the disks produced are not compatible with any PC that does
have the applications installed (or at least a suitable driver). The system
also has a reliability problem because the writing routines are unable to
accurately locate individual data blocks on the CD and have to leave large
gaps between successive writes. It works most of the time, but occasionally
a disk gets corrupted.
Hope that makes it clearer.
