程序代码：

%define bootseg    0100h
  %define buffseg    09000h
  %define buffoffset 0200h
  %define fatseg     08000h

        org 0100h
        jmp short LABEL_START        ; Start to boot.
    nop                ; 这个 nop 不可少

    ; 下面是 FAT12 磁盘的头
    BS_OEMName    DB 'ForrestY'    ; OEM String, 必须 8 个字节
    BPB_BytsPerSec    DW 512        ; 每扇区字节数
    BPB_SecPerClus    DB 1        ; 每簇多少扇区
    BPB_RsvdSecCnt    DW 1        ; Boot 记录占用多少扇区
    BPB_NumFATs    DB 2        ; 共有多少 FAT 表
    BPB_RootEntCnt    DW 224        ; 根目录文件数最大值
    BPB_TotSec16    DW 2880        ; 逻辑扇区总数
    BPB_Media    DB 0xF0        ; 媒体描述符
    BPB_FATSz16    DW 9        ; 每FAT扇区数
    BPB_SecPerTrk    DW 18        ; 每磁道扇区数
    BPB_NumHeads    DW 2        ; 磁头数(面数)
    BPB_HiddSec    DD 0        ; 隐藏扇区数
    BPB_TotSec32    DD 0        ; 如果 wTotalSectorCount 是 0 由这个值记录扇区数
    BS_DrvNum    DB 0        ; 中断 13 的驱动器号
    BS_Reserved1    DB 0        ; 未使用
    BS_BootSig    DB 29h        ; 扩展引导标记 (29h)
    BS_VolID    DD 0        ; 卷序列号
    BS_VolLab    DB 'Tinix0.01  '; 卷标, 必须 11 个字节
    BS_FileSysType    DB 'FAT12   '    ; 文件系统类型, 必须 8个字节
   
    root_dir_sector equ 19
    dir_sector_num  equ 14

LABEL_START:
        mov ax,cs
    mov ss,ax
        mov ds,ax
    mov sp,buffoffset
        mov bp,buffoffset
       
    push 1
    push buffseg
    push 0
        push root_dir_sector
read:   call read_disk
       
        call cmpstr

        cmp  ax,1
        je   load
    add  byte[bp-8],1
        cmp  byte[bp-2],dir_sector_num
        jae  notfindfile
    jmp  read 


load:
        add  sp,8
   
    add  di,15
        sub  sp,8
    push word[es:di]
        push 0203h
    push 014h
    push 0
   
       
       
        mov ah,0
    mov bl,0
    int 13h
      
        mov ax,[bp-4]
    mov cx,[bp-6]
    mov dh,[bp-8]
        mov bx,buffoffset
    int 13h

        mov ax,[bp-2]
   
    mov ax,[bp-2]
    add sp,6
zzyy:    mov bx,12
    mul bx
    mov bx,8
    div bx
    add ax,buffoffset
    mov si,ax
    mov ax,[es:si]
    cmp dx,0
    jne xxxz
   
    mov bx,0fh
    and bx,ax
    shr bx,8
    shl ax,8
        or  ax,bx
    jmp mmm
   
xxxz:
    mov bx,0f000h
    and bx,ax
    shl bx,12
    and ax,0ffh
    shr ax,4
    or  ax,bx
   
mmm:    cmp  ax,0ff8h
    jae  endo
    cmp  ax,0ff7h
    je   huaikuai
    push ax
    jmp  zzyy  

endo:   
    mov si,bp
    mov dx,buffoffset
xx23:    sub si,2
    push si
        mov ax,[es:si]   
    cmp cx,sp
    je  jmpbin
   
    push bp
    mov  bp,sp
   
    push 1
    push buffseg
    push dx
   
    call read_disk
    pop dx
    add sp,4
    pop bp
   
    add dx,512
    pop si
    jmp xx23
jmpbin:
    jmp [es:buffoffset]

notfindfile:
    mov     ax,cs
        mov     es,ax
    mov     cx,strlen2
    mov     dh,0
    mov    ax, BootMessage2
    mov    bp, ax            ; CX = 串长度
    mov    ax, 01301h        ; AH = 13,  AL = 01h
    mov    bx, 000ch        ; 页号为0(BH = 0) 黑底红字(BL = 0Ch,高亮)
    mov    dl, 0
    int    10h
        pop bp                ; 10h 号中断

huaikuai:
    jmp $
   
read_disk:
      mov ah,0
      mov bl,0
      int 13h
     
          mov ax,[bp-8]
          xor dx,dx
     
      mov bx,[BPB_SecPerTrk]
          div bx
   
      add dx,1
          mov cl,dl
      
      push ax
      shl  ax,1
          mov  ch,al
         
          pop  ax
      and  al,1
          mov  dh,al
          mov  dl,0
      mov  ax,[bp-4]
      mov  es,ax
      mov  bx,[bp-6]
xxx:      mov  al,[bp-2]
      mov  ah,02h
      int  13
          jc   xxx
      ret

cmpstr:
      mov  di,buffoffset
hhh:      push di
      mov  si,[search_str]
      mov  cx,search_strlen
          cld
          REPE cmpsb
          jcxz find
      pop  di
          add  di,32
      cmp  di,512+buffoffset
      jae  cmpend   
      jmp hhh
find:
         mov ax,1
     jmp findend
cmpend:
         mov ax,0   
findend:
       
         ret
      

     
BootMessage2        db      "not find mode32.bin"
strlen2                 equ     $-BootMessage2
BootMessage1            db      "LOADING mode32.bin"
strlen1                  equ     $-BootMessage1
search_str:             db      "MODE32  BIN",0
search_strlen           equ     $-search_str


times     510-($-$$)    db    0    ; 填充剩下的空间，使生成的二进制代码恰好为512字节
dw     0xaa55