extrn	.dos
;
curdsk	equ	25
;
; If fcb de^ uses default drive, lock it to current drive.
; This allows drive switches after file is opened.
; a,f
.drvlock::
	ldax d	! ora a ! rnz;	not on default drive
	mvi	a,curdsk
	call	.dos
	inr a	! stax d;	else lock to current drive
	ret