gram@uctcs.uucp (Graham Wheeler) (10/23/90)
A friend of mine has written a computer game, and he would like to try to sell it. He wants some form of simple copy protection (just to prevent the basic DOS commands from copying the disk). I said I would try to do this for him. My approach has been to try to either: i) Format a 41st track on a 40 track diskette ii) Format one track with 4 1024-byte sectors Obviously in each case I would want to be able to read and write a signature sector. Anyway, I've failed. I've tried changing the drive parameter table, and the disk media info on track 0, and then using the BIOS format-track service to do the job. I haven't had any joy. In the case of 1024-byte sectors, I don't get an error when I use the format service, but read/write services give me a bad address mark. The extra track just fails (except on high-density drives, but that's no good). I am using the interrupt 13h services, but thru int 40h (as DOS alters the 13h vector, but the 40h vector seems right - I checked by running my BIOS through Sourcer). Has anyone tried to do this, and have any ideas? The original idea came from Peter Norton's Programmer's Guide to the IBM PC, which states that these are common techniques for copy protection. He hinted that it was a straightforward task, but it ain't. In fact, I'm about to give up - this is my last resort (I could go and write a low-level disk device driver, but hell, I'm just doing this as a favour - I've spent too much time on this already...) Graham Wheeler | "Don't bother me, Data Network Architectures Lab| I'm reading a `Crisis'!" Dept. of Computer Science | Internet: <gram.uctcs@f4.n494.z5.fidonet.org> University of Cape Town | BANG: <...uunet!ddsw1!olsa99!uctcs!gram>