DOS dead guest star can break the endless loop of the program. Press Ctrl + ESC to immediately return the dead program to the DOS shell.

// -- DOS dead guest star, which can break the endless loop of the program. Press Ctrl + ESC to immediately return the dead program to the DOS shell.

Code segment
Assume Cs: code, DS: Code
Org 100 h
Start: JMP install
Oldint dd 100 h DUP (?)
Oldmcb dd 10 h DUP (?)
Oldint2f dd?
Oldint09 dd?
Oldint21 dd?
Sign db 0
Newint21: CMP ah, 0ah
Jnz newint21end
MoV Cs: byte PTR sign, 0ffh
Pushf
Call Cs: oldint21
MoV Cs: byte PTR sign, 0
Retf 2
Newint21end: JMP Cs: oldint21
Newint2f: CMP ah, 98 h
JZ lop1
JMP Cs: oldint2f
Lop1: mov Al, 98 h
Iret
Newint09: PUSH AX
In Al, 60 h
CMP Al, 01
JZ lop2
Exit: Pop ax
JMP Cs: oldint09
Lop2: mov ah, 02 h
Int 16 h
And Al, 0100b
JZ exit
MoV Al, CS: byte PTR sign
CMP Al, 0ffh
JZ exit
Lop4: in Al, 61 H
Or Al, 80 h
Out 61 H, Al
And Al, 7fh
Out 61 H, Al
MoV Al, 20 h
Out 20 h, Al
MoV ax, CS
MoV ds, ax
Dec ax
MoV es, ax
XOR Di, Di
MoV Si, offset oldmcb
MoV CX, 10 h
ClD
Rep movsb
MoV Si, offset oldint
XOR ax, ax
MoV es, ax
XOR Di, Di
MoV CX, 200 h
CLI
ClD
Rep movsw
STI
Push CS
Pop BX
MoV ah, 50 h
Int 21 h
MoV dx, offset word1
MoV ah, 09 h
Int 21 h
MoV dx, offset install
MoV ah, 31 H
Int 21 h
Word1: DB 10, 13, 7, 'goback has let your computer come to life! $'
Word2: DB 10, 13, 7, 'goback has installed! Only press Ctrl + ESC, when the computer is dead! $'
Word3: DB 10, 13, 'goback installed OK! '
DB 1.0, 13, 7, 'ver Author: Zhao Jibin 1998.7.29'
DB, 'When your computer is dead ....'
DB, 'You need to press Ctrl + ESC come to life... ',' $'
Install: mov ah, 98 h
Int 2fh
CMP Al, 98 h
Jnz lop3
MoV dx, offset word2
MoV ah, 09 h
Int 21 h
MoV ah, 04ch
Int 21 h
Lop3: Push CS
Pop DS
MoV ax, 352fh
Int 21 h
MoV word PTR oldint2f, BX
MoV word PTR oldint2f + 2, es
MoV ax, 3509 H
Int 21 h
MoV word PTR oldint09, BX
MoV word PTR oldint09 + 2, es
MoV ax, 3521 H
Int 21 h
MoV word PTR oldint21, BX
MoV word PTR oldint21 + 2, es
MoV ax, 252fh
MoV dx, offset newint2f
Int 21 h
MoV ax, 2509 H
MoV dx, offset newint09
Int 21 h
MoV ax, 2521 H
MoV dx, offset newint21
Int 21 h
Push CS
Pop es
XOR ax, ax
MoV ds, ax
XOR si, si
MoV Di, offset oldint
MoV CX, 200 h
ClD
Rep movsw
MoV ax, CS
Dec ax
MoV ds, ax
XOR si, si
MoV Di, offset oldmcb
MoV CX, 10 h
ClD
Rep movsb
Push CS
Pop DS
MoV dx, offset word3
MoV ah, 09 h
Int 21 h
MoV dx, offset install + 120 h
MoV Cl, 04 H
SHR dx, Cl
MoV ah, 31 H
Int 21 h

Code ends
End start