001D - Hook int21h

title hooked.asm
.model small

.code
cr equ 0ah
lf equ 0dh

nagusia proc near
hasi:
 mov ax,@code
 mov ds, ax

 mov ax,3509h
 int 21h

 mov cs:word ptr int21zahar,bx
 mov cs:word ptr int21zahar,es
 mov ax,2509h
 lea dx,int21hberri
 int 21h

 mov ah, 4ch
 int 21h

int21hberri:
 mov ah,09h
 lea dx,mezua
 int 21h
 jmp cs:int21zahar
 mov ax,0cacah
 iret

nagusia endp
mezua db 'Harrapatuta!',cr,lf,'$'
int21zahar dd 0
dta db 128 dup(?)
end hasi