PAGE ,132 ; Install an Interrupt 24 (DOS critical error exception) handler ; ; Public domain by Bob Stout ; ; Requires MASM 5.1 or later or equivalent ; ; Assemble with: MASM /Mx /z ... ; TASM /jMASM /mx /z ... % .MODEL memodel,C ;Add model support via command ;line macros, e.g. ;MASM /Dmemodel=LARGE .DATA? PUBLIC cedevdvr, cetype, ceerror, cereturn _origvec dd ? _newvec dd ? cedevdvr dd ? cetype dw ? ceerror dw ? cereturn db ? .CODE ; ; This is our actual ISR ; myint24: push ds ;save registers which may be push es ;required in case "Retry" is push bx ;selected push cx push dx push si push di push bp mov word PTR cedevdvr,si ;save device driver header address mov word PTR cedevdvr+2,bp mov cetype,ax ;save error type information mov ceerror,di ;save error code information call far PTR _newvec ;call our handler mov al,cereturn ;set up return code (abort, retry...) pop bp ;restore necessary registers pop di pop si pop dx pop cx pop bx pop es pop ds iret ; ; Call this to install our ISR ; ; void (_far *)() ins24(unsigned short segm, unsigned short offs); ; void (_far *)() ins24((void _far *handler)()); ; ; Paramters (option 1) - 1 : Segment of handler ; 2 : Offset of handler ; ; Paramters (option 2) - 1 : Address of handler ; ; Returns pointer to old handler ; ins24 PROC USES AX BX DS ES, segm:WORD, offs:WORD mov ax,3524h ;get old vector... int 21h mov word PTR _origvec,bx mov word PTR _origvec+2,es ;...and save it mov ax,offs ;load handler offset... mov word PTR _newvec,ax mov ax,segm ; & segment into _newvec mov word PTR _newvec+2,ax push cs ;get myint24 segment in DS pop ds mov dx, OFFSET myint24 ;install myint24 in int 24h mov ax,2524h ; into Interrupt 24h int 21h mov ax,word PTR _origvec mov dx,word PTR _origvec+2 ins24 ENDP ; ; Call this to uninstall our ISR ; ; void redo24(void); ; redo24 PROC USES AX BX DS mov dx, word PTR _origvec ;restore original vector mov ds, word PTR _origvec+2 mov ax,2524h int 21h ret redo24 ENDP end