Hi Formatting of disk is a little bit of black magic to most programmers. There is little information on things like the exact gap sizes used for different formats. Also, formating usually requires knowledge of the hardware actually used while simply writing preformatted sectors can usually be handled through simple system calls. If formatting the disk with the system is trivial, I see no reason to go through the extra process of doing so in the code. While if the program is intended to bootstrap the system with disk of unknown condition, formatting is a must. I've done both ways for my home stuff. Of course, if it is to be released to others, one should include a readme or help printout that states the need of a preformatted disk. Dwight formatted image on the disk and be done with it. thought were communications related, which disappeared when I formatted the disks. Interestingly, CP/M images seem to write just fine on DOS formatted disks so go figure.