20 Sep
2015
20 Sep
'15
12:28 p.m.
On Sun, 20 Sep 2015, Jon Elson wrote:
Well, one would assume this is also OS specific. I
would guess it would be
incredibly hard to make a "disk" virus that would work on greatly differing
OS's like Linux AND Windows. No telling what would happen if one of these
disk viruses got onto a hard drive on a Windows system and then the drive was
reformatted and loaded with Linux.
Most likely you'd have odd crashes or something.
It is possible to create an executable file that identifies the OS that it
is running on and does a conditional jump to different code, assuming that
the processor uses the same instruction set.
How different the OS's are would determine how much code could be shared.
If they are very different, then the executable file could be twice as
large, with no code in common.
It is even possible to make a disk that is readable as multiple disk
formats, so long as each is expecting the DIRectory tracks to be in
different places.
One of the many projects that I never got ready for market was to make a
multi-platform distribution format for software. "Save a few cents on
media costs by putting all of your platforms on one disk" But, after
August 1981, it eventually became apparent that the need for such was not
going to be around much longer.
If the boot code is short enough, it is even possible to have an FM, an
MFM, and a GCR boot sector in the same boot track, since each will not
even see any except its own. Formatting/recording a track with mixed
densities and/or encodings and multiple sector sizes is not a supported
function in most operating systems, nor even FDCs, but can be done with
some flux transition controllers.