name	cls 
;
; subroutine cls : assembly language routine that uses the video
; bios call to clear the screen
;
; fortran call is : call cls 
;
;
;	interface to IBM professional fortran 1.0

stack_size	equ	6	; number of bytes needed on stack

data		segment
		db	'cls     '
sp_save	dw	?
		dd	cls 
		dd	0
data		ends



;
code		segment	'code'
		assume	cs:code,ds:data,es:nothing,ss:nothing
		public	cls 
cls 		proc		far


;----------execute Profort standard entry linkage--------------------

		push	ds
		sub	bp,stack_size+6
		mov	ax,data
		mov	ds,ax
		mov	sp_save,sp
		mov	sp,bp
;---------------------------------------------------------------------

;	make call for video parameters to get the number of the
;	active page needed by the video bios set cursor command

		mov	ah,15		; get current video state
		int	10h		; call video bios

		mov	cx,0		; upper left corner is (0,0)

		mov	dx,184fh	; assume lower right corner at (24,79)
		cmp	ah,80		; but make sure were in 80 colimn mode
		jz	is_wide

;	if we get here, were in 40 column mode... so adjust dx to...

		mov	dl,27h	; (24,39)
is_wide:
		mov	bh,7		; set display attribute
		mov	al,0		; get set to scroll entire screen
		mov	ah,6		; set scroll screen function
		int	10h		; call video bios


;-------------perform exit linkage------------------------------------

		add	sp,stack_size+2
		ret
;---------------------------------------------------------------------

cls 		endp
code		ends
		end

stack		segment word stack 'stack'
		db	stack_size dup(?)
stack		ends
		end
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