> Am I to understand that if you burn audio disks, you have to
> do it all in one session, so that a TOC is written?
>
> But, for data storage, you can write some files now
> and then later and then later, so that it is somewhat
> like a floppy?
>
> For example, I would like to back up some files (old games)
> to a cd.  I can write some now.  Then next week write
> some more?
>
> It makes no difference to me if it is write
> once or write many, as I would keep it.  (The price of
> cd-r has come way down.)  I have some games that
> I downloaded patches for.  I have no permanent place
> to store these patches, but copy them from disk to
> disk.

        Well you have opened a HUGE can of worms here, but I'll give it a try, to
begin, Audio:
        Audio CDs have to have all of the tracks written in one session, once you
close an audio CD you can write as many additional tracks as you want, but a
CD player will only recognize what was in the first session. Now, this isn't
so bad because with an audio CD since you don't have to close the session
after you burn tracks. You can burn a bunch of tracks, leave the session
open, come back and burn more tracks. However, no CD player will play you
disc until you close the session. Once you close the first session on an
audio disc you can add additional sessions, but to be useful they must be
data tracks since no CD player (that I know of) will read past the first
session. Commercial audio CDs use this method to put data on the discs, the
first session is audio, the second data. The problem is some older CDROMs
will not read an audio disc past the first session so the data is not
readable on those drives, this problem doesn't really exist in newer drives
anymore.
        Now to data. If you thought audio was complicated, then data will look
horrific! With data you can't really burn some data and leave the session
open using normal CDR burning software (packet writing software does, but
that's coming...) However, since most current CDROMs can read more than one
session, nothing stops you from burning a bunch of sessions to a disc,
leaving the disc open after every burn. As long as you inherit the old
session when burning the new one your disc will work and be fully
accessible. The only caveats with this method is each time you burn a
session you use about 30MB for the first session and another 10MB each for
every additional session; with today's CDR prices though that isn't as bad
as it used to. The other problem with this method is the amount of data on
your CD will not reflect what Windows explorer reports. Windows explorer
only reports the size of all the files in the last session burned, while all
the sessions are there it will still be inaccurate. The biggest problem with
multisessioning like this is that some CDROMs don't like it, but there is
nothing that can be done about this except not to multisession.
        Packet writing software (DirectCD is an example) let's you do with data
what I described with audio, you can add to a session as often as you like,
you only have to close it when you want to be able to read the CD in
something other than a computer with the "special software". This enables
you to treat a CD as you would a floppy, you can add files whenever you
want. While the software does allow you to "delete" files on the CD, the
space used by those files is NOT recovered on CDR media (it is on CDRW, more
on that later). The problem with this method is many CDROMs that will read
multisession CDRs cannot read packet written CDRs since each time you burn
to the session the laser power was slightly different, resulting in some
parts of the disc being darker than others. MANY CDROMs can't handle this
varying reflectivity. For example, I have a 10X pioneer CDROM that reads
multisession discs without a problem, however, when I close a DirectCD
session and try to read it in the 10X it chokes on some files and not
others.
        Everything I have said here is identical in the CDRW world, you can make
audio CDs, multisession data CDs, etc., however packet software usually
formats the CDRW in such a way as to allow you to delete files on the disc
and recover the space used. This sounds great, until you find out that this
"ability" uses up 150MB on the space on the CDRW. A DirectCD CDRW disc only
has 500MB of space available. What I wish is that DirectCD would allow me to
choose whether I wanted the ability to recover deleted space or not, that
way I could choose if 150MB was worth it.
        I hoped this VERY long email helped, I am certain I left out some parts but
I hope I gave at least a partially understandable overview of the
complicated world of CDR(W). TTYL

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