The point is that the file ISO-9660 sys is so easy for cd that it looks like there no file sys, remember that a cd is written so a file or dir will be in one block, so all address are at a set address, other than files/die, so once you have the start address for the file to load, you just load 2048 byte chuncks, some times you need to jump other a header, untill you have load file etc.
Theres no cluster chains, just a easy to load small chucks of the file, that are all placed one after the other . :) .
PS: If you download this
http://www.dex4u.com/dexiso.zip
burn it to cd-rw and you will be able to read the full cd using Dex4u cd driver.