;Library Name: ARRAYLIB
;Module Name: SETDU
;Author: Al Hawley
;Date: 31 Mar 1987
;Version number: 1.0c

;Version History:
	
;Program Function: ARRAYLIB is a collection of subroutines which
;	implement the management of byte arrays in programs written
;	for Z80 or HD64180 based computers. This module is one of the
;	set, and may require the presence of others.

;***************************************************
;		COPYRIGHT NOTICE
;ARRAYLIB is copyright by A. E. Hawley on March 4, 1987.
;It may be freely distributed, but it must not be sold 
;either separately or as part of a package without the 
;written consent of the author.  The author may be reached 
;via electronic mail at the Ladera Z-Node in Los Angeles,
;213-670-9465, or by Voice Phone at: 213-649-3575
;
;***************************************************

	MACLIB	ARRHDR

	name setdu
;This module contains the following routines:
	public arrsetdu
;..and uses the following external routines:
	ext arxltbit,arrxltrc,arresbit,arsetbit

arrsetdu:
;set the bit corresponding to disk/user to 0
;or 1, according to the value in reg a.
;on entry,
;	a	= 00 or >0
;	bc	= disk, user
;on exit,
;	bit at du is set(1) if a was non-zero
;	bit at du is reset(0) if a was zero
;all registers are destroyed

	ex	af,af'
	dec	b		;convert disk to row(0..)
	call	arxltbit
	call	arrxltrc	;addr in hl, bit loc in e
	ex	af,af'
	or	a		;was reg a 0?
	ld	a,e
	jp	z,arresbit	;reset bit if a was 0
	jp	arsetbit	;else set the bit

;**********************************************

	end