;
;Program to initialize the entire 128 bytes of the shell stack 
;This is necessary for Wordstar CPM Version 4 only
;November, 1987--Biff Bueffel
;
Z3ENV	equ	0fe00h		;for debugging purposes only
shsize	equ	128		;usual size of shell stack
;
	org	100h
	jp	start
	db	'Z3ENV'
	db	1
z3eadr	dw	Z3ENV		;Z3ENV address
start:
	ld	hl,0		;save CPM stack
	add	hl,sp		;
	ld	(cpmstk),hl	;	
	call	shloc		;get address of z3shell stack
	call	inshl		;initialize shell stack
	ld	hl,(cpmstk)	;get CPM stack
	ld	sp,hl		;
	ret			;back to CPM
;
;	Find and save shell stack address
;
shloc:	ld	hl,(z3eadr)	;get z3env address
	ld	a,30		;offset to find shell stack address
	add	a,l		;add offset to l
	ld	l,a		;place result in l
	xor	a		;zero a
	adc	a,h		;add any carry to h
	ld	h,a		;place result in h
	ld	a,(hl)		;get low byte shell stack address
	ld	(shladr),a	;store it
	inc	hl		;bump pointer
	ld	a,(hl)		;get high byte shell stack address
	ld	(shladr+1),a	;store it
	ret
;
;	Initialize the shell stack
;
inshl:	ld	hl,(shladr)	;get shell stack address into hl register
	ld	b,(shsize)	;128 bytes
zerom:	ld	(hl),0		;0 memory
	inc	hl		;point to next byte
	djnz	zerom		;
	ret
;
shladr	ds	2		;storage for shell stack address
cpmstk	equ	$
end	start