; quick-and-dirty screen grabber
DOSSEG
.MODEL SMALL
.STACK 4096

.DATA

.CODE                   ; use only one segment to make life easier

VideoSegment EQU 0B800h ; force program to use VGA mode screens

VideoStore         db 4000 dup (?)   ; storage area for data

Old9  label  FAR        ; define old interrupt 9 as far procedure

int9 PROC               ; start of ISR for 9h
; ... still to be written
int9 ENDP

EndofCode:              ; end of resident part of code

ProgramStart:
 mov  ax,cs             ; set data segment = code segment
 mov  ds,ax
 
 mov  ax,3509h          ; get original interrupt vector 9h
 int  21h
 mov  word ptr Startof9+1,bx   ; patch old procedure address into code
 mov  word ptr Startof9+3,es

 lea  dx,int9           ; set interrupt vector 9h
 mov  ax,2509h
 int  21h

 lea  dx,EndOfCode      ; get length of code to remain resident
 mov  cl,4              ; divide by 4 to calculate paragraphs
 shr  dx,cl
 add  dx,11h            ; add 1 for remainder and 10 for PSP
 mov  ah,31h            ; terminate and stay resident
 int  21h

END ProgramStart