How to erase the partition table in MS-DOS?

Question

Is there any way to erase the partition table in MS-DOS? I've tried looking at the fdisk command, but that is an interactive interface. I want a single command that does not show any output and doesn't need user input.

Answer 1

MS-DOS comes with a program called debug. Instructions for using it to erase the MBR interactively can found in many places, and the same input can be fed from a file using debug < script.txt.

Note: This erases the whole MBR – partition table and boot loader code.

Copied into a script file, the same commands would look like:

f 9000:0 200 0            ; zero out 512 bytes at 0x9000:0x0000
a                         ; enter assembly mode
mov dx,9000               ; dx=0x9000
mov es,dx                 ; es=dx
xor bx,bx                 ; bx=0x0000
mov cx,0001               ; ch=0x00 (track#) cl=0x01 (sector#)
mov dx,0080               ; dh=0x00 (head#) dl=0x01 (drive#)
mov ax,0301               ; ah=0x03 (write sectors) al=0x01 (sector count)
int 13                    ; INT 13h BIOS disk access
int 20                    ; INT 20h exit program
                          ; blank line
g
q

Note: I suspect directly writing the zeroed memory to sector 0 using the "write sectors" command would be much simpler than running custom assembly code, but I don't actually have a MS-DOS system around to test this.

f 9000:0 200 0            ; zero out 512 bytes at 0x9000:0x0000
w 9000:0 1 0 1            ; write 1 sector to drive 1
q

See also: More information about how to use DEBUG.