FD_DISK_WRITABLE_BIT
clear_bit(FD_DISK_WRITABLE_BIT,
set_bit(FD_DISK_WRITABLE_BIT,
clear_bit(FD_DISK_WRITABLE_BIT,
!test_bit(FD_DISK_WRITABLE_BIT, &drive_state[drive].flags))
#define FD_DISK_WRITABLE (1 << FD_DISK_WRITABLE_BIT)