DOS Boot Record
This boot record boots DOS 5.0 thru DOS 6.22
from a FAT12 or FAT16 partition.
This boot record is located in the first sector of a
physical primary DOS partition on a hard disk drive,
or the first sector of a floppy drive.
This is a ZIP archive that contains the boot record source code
and some batch files to construct the boot record.
This contents of this ZIP archive are:
This source file can be assembled, linked, extracted, and written to your hard
drive as real working boot code.
Click on the heading to view the source code.
- DOSPBR.ASM - DOS boot record source code (see below)
- MAKEFILE.BAT - Batch file to assemble/link/extract
- VERCODE.BAT - Batch file to verify the code
- DOSRAW.BAT - Batch file to extract and dasm the boot code using DEBUG
- DOSRAW.CMD - DEBUG commands used by DOSRAW.BAT
- DOSOLD.TXT - Original info found on the net
This batch file assembles, links, and extracts the boot code.
DOSPBR.ASM is assembled with MASM version 5.10 into DOSPBR.OBJ,
DOSPBR.OBJ is linked with LINK version 5.31 into DOSPBR.EXE,
DOSPBR.EXE is processed by the BOOTEXE utility to extract the boot record
This batch file verifies the new boot code with what's in the actual
boot record, or what's in a file. Customize to your preference.
Note that not all assemblers work the same -
some add slack bytes (nop's), other's don't.
This batch file uses DEBUG to disassemble the raw boot code.
The DEBUG commands are in the file DOSRAW.CMD.
The DEBUG output is then processed by the DBLFIX utility to clean it up.
This is some old disassembled boot code I found on the net.
Comments are sparse and sometimes inaccurate.
It took most of a day to clean up the code, comment it, and make it usable.
But, I did get to spray weeds today!
Utility programs used by this archive are:
You can get more info on these utilities and others by following the above links.