Thanks for the responses.
Those double d commands are marvellous; simple and yet effective. It even
produces a positive side-effect; a backup copy of the floppy image in the
harddisk. I don't know if I'm the only one with this problem; I read through
'dd' with 'man' but is left with the impression that it is only for files
copying. Which part indicates that it can do image copy?
More about the BIOS. In DOS machine, hardware diagnostics and initialization
is done by the BIOS. For instance, if the keyboard or mouse is not plugged
in, the diagnostic ...