; Program:  DATEREG
; Author:   Rick Charnes
; Date:     22 October 1987
;
; In Z80DOS the date is stored in memory locations 0050 and 0051.  The 
; hex values contained therein are the number of days in hex since 
; December 31, 1977.  In this form the date is entirely inaccessible for 
; use in aliases.  DATEREG take the date in the form contained in these 
; memory locations and puts it in the ZCPR3 registers.  Thus the $Rn 
; symbol in ARUNZ can be used to represent the date.
                
; The components of the date are represented as follows:
                  
; REGISTER 5 = mm, where 'yy' is the 20th century year
; REGISTER 6 = dd, where 'mm' is the month
; REGISTER 7 = yy, where 'dd' is the day
;
; Note that both REG.COM and the RCP-resident REG display the decimal 
; equivalent of the hex values held in the ZCPR3 registers.  Therefore, 
; using these commands will NOT display what you might have hoped.  
; ARUNZ's '$Rn' symbol, however, displays the ZCPR3 registers in their 
; native hex form, which is exactly how we want it to appear since it
; is only in the hex format that the date reads accurately.

; DATERG would of course not be possible without Carson Wilson's superb 
; Z80DOS.  This program in particular uses DATEHL.REL written by Carson 
; and supplied in Z80DOS10.LBR.
;
; DATEREG prints nothing on the screen.

; External Z3LIB and SYSLIB Routines
;
	ext	z3init,putreg,qprint,datehl
;
; Program beginning
;
	jp	start
	db	'z3env'
	db	3		; Type 3 environment
z3env:	dw	0fe00h
;
; Initialize environment for Z3 routines

start:	ld	hl,(z3env)
	call	z3init

	ld	hl,(50h)
	call	datehl		; Carson Wilson's linkable routine

; PUTREG takes whatever is in B and makes that the ZCPR3 register
; number, and whatever in A the register value.

put:	ld	b,6	; First we deal with ZCPR3 register 6.  
                        ; Calling DATEHL has already put the BCD day
                        ; into A, so day gets put into register 6.
	call	putreg	
	ld	b,7	; ZCPR3 register 7
	ld	a,h	; H contains BCD 20th century year, PUTREG 
			; puts it into ZCPR3 register 7.
	call	putreg

	ld	b,5     ; ZCPR3 register 5
	ld	a,l	; L contains BCD month, which PUTREG will put
			; into register 5.
	call	putreg

	end