John,
You understand the process very well. The image is written, then the software
adds "lead-out" information that tells the player where the data starts and
stops on the disc.
It seems redundant, but the TAR utility and the premastering program are
similar in that each makes one large file out of your collection of directories
and files. TAR (which stands for Tape Archive/Retrieval) is used to write to
tape because otherwise you'd lose the directory structures. Premastering
software serves a similar function for CDs, which are recorded in one large
spiral on the disc. (Large is right — 3 miles long in the case of a 74
minute/650MB disc.)
Kathy Cochrane
Section 6 Sysop