Digital-Research-Source-Code/MPM OPERATING SYSTEMS/MPM-86/MISC DRI DISKS/25/LIOS.MAC

;
;	GENERALLY USEFUL DEFINES
; 
TRUE	EQU	0FFFFH
FALSE	EQU	0H
ESC	EQU	27
TXMOD	EQU	0FFH
;
;	SWITCH TABLE FOR OPTIONAL ENTRY POINTS
;
USEGLINE	EQU	FALSE 	
;	
;	MSX ROM BIOS ENTRY DEFINITIONS
;
BIOSVEC EQU	01H		; Good 'ol CP/M bios jmp vector address	
MSXBASE EQU	040H-03H	; CP/M bios additive base for MSX hooks
rdvrm	equ	004AH
wrtvrm	equ	004DH
setrd	equ	0050H
setwrt	equ	0053H
filvrm	equ	0056H
initxt  equ     006cH
inigrp  equ     0072H
grpprt	equ	008dH
setatr  equ	011aH
setc	equ	0120H
readc	equ	011dH
mapxyc  equ	0111H

cls     equ     0c3h  
linlen  equ     0f3b0h
ctrlg   equ     07h
;
;	DATA VARIABLES FOR LIOS
; 
	DSEG
SPLIT   DB    TXMOD
;
;	EXTERNAL AND VARIABLE FUNCTION DECLARATIONS
;
	EXTRN	bios		; 'C' bios call routine (stk oriented)	

GRPCGP	EQU     0F3CBH		; start of pixel ram in VDP
GRPCOL  EQU	0F3C9H		; start of color RAM in VDP
GRPACX	EQU	0FCB7H		; Graphics position for text
GRPACY	EQU	0FCB9H		;    y 
BAKCLR	EQU	0F3EAH		; Background color
VDPDR	EQU	00098H		; VDP read register port
VDPDW	EQU	00098H		; VDP write register port
VDPCW	EQU	00099H		; VDP control register port

	CSEG
;************************************************************************
;								       	*
;		SECTION: Utility routines for MSX LIOS        		*
;									*
;************************************************************************

FASTMSX:
	push	d		; save potential parameter
	xchg			; put desired vector into hl
	lhld	BIOSVEC		; get address of CP/M BIOS jmp vector
	dad	d		; calculate entry in jump table
	pop	d		; restore de
	pchl			; go for it!

;
;	This version is slower, but preserves all register (inc. HL)
;
FULLMSX:
	push	h		; save potential parameters
	push	d		;
	lxi	h,6		; get MSXBIOS address desired (on stack)
	dad	sp		;
	mov	e,m		;
	inx	h		;
	mov	d,m		;
	lhld	BIOSVEC		; get address of CP/M BIOS jmp vector
	dad	d		; calculate entry in jump table
	pop	d		; restore de
	xthl			; restore hl and put target address on stack
	ret			; jmp (sp) -- with pop thrown in, too!

;************************************************************************
;								       	*
;		SECTION: Initialization and State Information  		*
;									*
;************************************************************************

	;---------------------------------------------------------------
	; GINIT
	;
	; Parameters:	None
	; Returns:	None.
	; Description:  Does all hardware and graphics initialization
	;		(if necessary). This routine is called before
	;		any other LIOS routine.
	;---------------------------------------------------------------

	PUBLIC	GINIT
GINIT:
	;
	; GINIT is the first call made to the LIOS. Any initialization
	; for graphics, cursor addressing, screen management, hardware
	; initialization, etc. should be performed here.
	;
	lxi	h,0		; Enter graphics mode
	push	h		; (fullscreen)
	call	GRAFON		;
	pop	h		; discard parameter
	ret

	;---------------------------------------------------------------
	; EXIT
	;
	; Parameters:	None
	; Returns:	None.
	; Description:  Returns to operating system. Does any necessary 
	;		cleanup.
	;---------------------------------------------------------------

	PUBLIC	EXIT
EXIT:	
	; Terminates Logo interpreter. Any cleanup work for proper exit 
	; should be done here (e.g. close files, reset graphics, etc.)

        pop     h	; discard return address
        lxi     h,0	; substitute address 0 (warm boot)
        push    h	;
        jmp     TEXTON	; Usually, just do a CP/M warm boot

	;---------------------------------------------------------------
	; TEXTON
	;
	; Parameters:	None
	; Returns:	None.
	; Description:  Sets text only mode. All character output, cursor
	;		addressing, clear screen, etc. should go to text
	;		plane only. In systems with only a single logical
	;		screen., either clear graphics or do buffering.
	;---------------------------------------------------------------

	PUBLIC	TEXTON
TEXTON:
	;
	; Sets up character I/O to the text plane. Any cursor variables,
	; mode information, and buffer management should be done here.
	; Managing the screen (e.g. cursor positioning and clearing screen),
	; are performed by Logo .
	;
	push	b		;
	mvi	a,TXMOD		;
	sta	SPLIT		; flag in text mode
	lxi	h,MSXBASE+initxt; use MSX init text code
	call	FASTMSX		; access through CP/M MSX BIOS
	pop	b		;
	ret

	;---------------------------------------------------------------
	; GRAFON
	;
	; Parameters:	Splitline: integer, range 0..GRAFROWS
	; Returns:	None.
	; Description:  If splitline is 0, then if FULLSCREEN graphics 
	;		mode. Any text commands should be either buffered,
	;		hidden in text plane (if TWOSCR = 1), or ignored.
	;
	;		If splitline <> 0, then the parameter indicates
	;		the first line of the split screen (SPLITSCREEN).
	;		Text and graphics should appear on display
	;		together, each in their respective areas. If
	;		TWOSCR = 0, then Logo clips graphics output
	;		at splitline; otherwise all graphics output goes
	;		to full screen.
	;---------------------------------------------------------------

	PUBLIC	GRAFON
GRAFON:
	; 
	; Indicates that Logo is in either FULLSCREEN or SPLITSCREEN
	; mode. This turns off character output to the text plane and
	; turns on character and line drawing output to the graphics
	; plane. If splitrow is zero, then the mode is FULLSCREEN, else
  	; splitrow gives the starting row of where text should be placed
	; in the graphics buffer.
	;
	EXTRN	draw_t

	lxi	h,2		; [bc] [ret] [splitline] stacked
	dad	sp		;
	lda	SPLIT		; check old split row
	inr	a		; Are we coming from text mode?
	mov	a,m		; save new split first
	sta	SPLIT		; use the split row for char I/O
	rnz			; Don't re-initialize if in graphics II
	push	b		; save bc
	lxi	h,MSXBASE+inigrp; turn on MSX's graphic II mode 
	call	FASTMSX		; init to graphics II mode
	call	draw_t		; **FIX for ENG RELEASE (TWOSCR = 0)
	pop	b		;
	ret


;************************************************************************
;								       	*
;		SECTION: Screen Interface		       		*
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; XCONIN
	;
	; Parameters:	None
	; Returns:	ch from console in L reg. (H is 0)
	; NOTE:		Waits until ch is typed!
	;---------------------------------------------------------------

	PUBLIC	XCONIN	
XCONIN:
	push	b	; Must save bc register (Linkage convention)
;
;	NOTE: 	A bios call mechanism is incorporated into the Logo 
;		package. The entry point is "BIOS", which takes a
;		single integer parameter that is the number of the BIOS
;		call. The return value is properly stored in HL with the
;	        Z flag set/reset.
;
;			e.g.   bios(3) does a CONIN call.	
;		
;
	lxi	h,3	; CONIN vector number
	push	h	; set up parmeter for call
	call	bios	; get next character
	pop	d	; remove parameter
;
	pop	b	; Restore bc
	ret

	;---------------------------------------------------------------
	; XCONST
	;
	; Parameters:	None
	; Returns:	console status in HL: zero    -> no ch
	;			    	      nonzero -> ch ready
	;---------------------------------------------------------------

	PUBLIC	XCONST
XCONST:
	push	b	; Must save bc register (Linkage convention)
	lxi	h,2	; Make CP/M bios console status call
	push	h	; set up parameter
	call	bios	; get status 
	pop	d	; Discard parameter
	pop	b	; restore bc
	ret	

	;---------------------------------------------------------------
	; XCONOU
	;
	; Parameters:	ch: char, range 0..255
	; Returns:	None.
	; Description:  Outputs character to either graphics or text 
	;		area based upon current mode (see GRAFON and
	;		TEXTON). You should output character at current
	;		x,y coordinate and increment x (no need to check
	;		for scroll or eol)
	;---------------------------------------------------------------

	PUBLIC	XCONOU
	;
	; Do console output (both text and graphics screen)
	;
XCONOU:
	lxi	h,2		; [ret] [ch] stacked
	dad	sp		; HL set up to obtain parameter
	mov	a,m		; A := ch
BIOS4:
        lxi     h,0
        mov     l,a
 	lda	SPLIT		; in graphics II mode?
	inr	a		;
	jnz	GCONOUT		; if so, do graphics text I/O
	push	b		; save bc register
        push    h
        lxi     h,4
        push    h
        call    bios
        pop     h
        pop     h
	pop	b
        ret           

GCONOUT:
	push	b		; ch to output in [l]
	mov	a,l		;
	lxi	h,MSXBASE+grpprt; do graphics ch output
	call	FASTMSX		;
	pop	b		;
	ret
	
	;---------------------------------------------------------------
	; CLRSCR
	;
	; Parameters:	top: integer, range: 1..(SCRROWS or GRAFROWS)
	;		bot: integer, range: 1..(SCRROWS or GRAFROWS)  
	; Returns:	None.
	; Description:  Clears text area from row top to row bot 
	;
	; Update Hist:	Modeled code after VT-52 handler in z19lios
	;		SJS 5-2-84
	;---------------------------------------------------------------

	PUBLIC  CLRSCR
CLRSCR:
	push	b	; save BC
	lxi	h,4	; [bc] [ret] [top] [bot] stacked
	dad	sp	; HL set up to obtain parameters
        mov     b,m     ; get top (REG B)
        inx     h	;
        inx     h	;
        mov     c,m     ; get bottom (REG C)
	lda	SPLIT	; test mode
	inr	a	;
	jnz	GCLR	;
CLRSC1:
	mov	a,c	; get bottom line
	cmp	b	; compare to current line
	jc	clrsc2	; done if current line > bottom line 
	mvi	h,0	;
	mov	l,b	; push current line number
	push	h	;
	mv<6D>	l,<2C>	; pus<75> colum<75> position
	push	h	;
	call	SETXY	; go to the selected position
	pop	h	; remove parameters
	pop	h
	mvi	a,ESC	; set clear line sequence ESC K
	call	bios4	; write character
	mvi	a,'K'	; get K
	call	bios4	;
	inr	b	; bump line number & loop
	jmp	CLRSC1	;
	
clrsc2:
        pop     b
        ret

GCLR:
	dcr	b	; make top zero relative
	mvi	l,0	;    and multiply by 256
	mov	h,b	;
	mov	a,c	; get bot
	sub	b	; get # lines to clear
	mov	b,a	;     and multiply by 256 to convert to bytes
	mvi	c,0	;
			; HL = start adr, BC = count
	call	clrvdp	; and clear the area
	pop	b	;
	ret

	;---------------------------------------------------------------
	; SETXY
	;
	; Parameters:	x: integer, range: 1..(SCRCOLS or GRAFCOLS)
	;		y: integer, range: 1..(SCRROWS or GRAFROWS)  
	; Returns:	None.
	; Description:  Sets cursor to row x, column y 
	;---------------------------------------------------------------
	;
	; set cursor to column x and row y
	; x and y are 1 relative -- upper left is SETXY(1,1)
	;

	PUBLIC	SETXY
SETXY:
	push	b	; save bc reg
	lxi	h,4	; get x and y
	dad	sp	;
	mov	b,m	; put X in b and Y in c
	inx	h	;
	inx	h	;
	mov	c,m	;
	lda	SPLIT	; test if in graphics II mode
	inr	a	;
	jnz	GSETXY	;
	mvi	a,ESC	; Set cursor addressing sequence (ESC Y ypos xpos)
	call	bios4	;
	mvi	a,'Y'	;
	call	bios4	; 
	mov	a,c	; get y
	adi	31	; 	and add 31	
	call	bios4	; 
	mov	a,b	; get x
	adi	31	;       and add 31
	call	bios4	;
	pop	b	; restore b
	ret		; and return
GSETXY:			
			; convert coordinates are in pixel values	
	mov	h,b	; get X
	dcr	h	; make zero relative
	mov	l,c	; get Y
	dcr	l	; make zero relative
	dad	h	; multiply both by 8
	dad	h	;
	dad	h	;
	mov	a,h	; get X (pixel value)
	sta	GRPACX	; and save
	mov	a,l	; get Y
	sta	GRPACY	;
	;call	GCURS	; turn cursor on at new position
	pop	b	;
	ret	 
	;---------------------------------------------------------------
	; SCROLL
	;
	; Parameters:	top: integer, range: 1..(SCRROWS or GRAFROWS)
	;		bot: integer, range: 1..(SCRROWS or GRAFROWS)  
	; Returns:	None.
	; Description:  Moves lines top-1 to bot up 1 line, line bot is
	;		cleared.
	;---------------------------------------------------------------

	PUBLIC	SCROLL

SCROLL:
	push	b	; save bc (if necessary)
	lxi	h,4	; [bc] [ret] [top] [bot] stacked
	dad	sp	; index to top
	mov	b,m	; HL set up to obtain parameters
	inx	h	; 
	inx	h	;
	mov	c,m	; b = top, c = bot
	lda	SPLIT	; check mode (TEXT or GRAPHICS)
	inr	a	;
	jnz	GSCROLL	; graphics II screen scroll
	mov	l,b	; get top in HL (zero h)
	mvi	h,0	;
	push	h	;
	mvi	l,1	; get column number
	push	h
	call	SETXY	; position at top of window to scroll
	pop	h	; remove parameter
	pop	h	;   .
	mvi	a,ESC	; Delete line at top (ESC M)
	call	bios4	; 
	mvi	a,'M'	; 
	call	bios4	;   
	mov	l,b	; get bot
	mvi	h,0	;
	push	h	;
	mvi	l,1	; get column number
	push	h	; 
	call	SETXY	; set position at bottom line of window to scroll
	pop	h	; remove parameter 
	pop	h	;    .
	mvi	a,ESC	; Insert line at bottom ESC 'L' (force scroll)
	call	bios4	;
	mvi	a,'L'	;
	call	bios4	;
	pop	b	; restore bc
	ret		; and return
	;
	; Scroll screen from top to bot. Delete line top, move (bot,top-1)
	; up to (bot-1,top). Clear line bot to spaces.
	;
GSCROLL:
	dcr	b		; make top line zero relative
	mov	a,c		; get bot line
	sub	b		; get # of lines+1 to scroll up
	mov	c,a		; save lines to scroll
scrlup:
	dcr	c		; done?
	jz	clrbot		;
	call	moveup		; move one line up (b has current line #) 
	inr	b		; bump to next line
	jmp	scrlup
clrbot:
	call	cline		; clear line at bot
	pop	b
	ret

moveup:
	mvi	a,255		; move 256 chars (1 line)
	mov	h,b		; get start address
	mvi	l,0		; 	which is 256*linenumber!
movloop:
	push	psw		; save loop count
	inr	h		;     and point to next line
	push	h		; save for awhile
	lxi	h,MSXBASE+rdvrm	; point VDP for buffer for  
	xthl			;
	call	FULLMSX		; read char int acc
	dcr	h		; point back at current line 
	xthl			; save some more
	lxi	h,MSXBASE+wrtvrm;
	xthl			;
	call	FULLMSX		; write char up one line
	pop	d		;
	inx	h		; point to next byte
	pop	psw		; get loop count
	dcr	a		;    and decrement
	cpi	0FFH		; all done ?
	jnz	movloop		;	
	ret			; go back

cline:
	mov	h,b		; get line number
	mvi	l,0		;     and multiply by 256 
	lxi	b,256		; number of bytes to fill
clrvdp:				; bc = # byte 
	xra	a		; clear to zeros
	push	h		; and save for awhile
	lxi	h,MSXBASE+filvrm; fill dat der memory
	xthl			;
	call	FULLMSX		; do it
	pop	d		;
	ret			;

;***********************************************************************
;								       *
;		SECTION: Graphics Interface		       	       *
;								       *
;***********************************************************************

	;---------------------------------------------------------------
	; GPLOT
	;
	; Parameters:	x: integer, range: 0..XDOTS-1
	;		y: integer, range: 0..YDOTS-1
	;		pen: 2 bytes (integer):
	;		     LSB: pen color    MSB: pen drawing mode
	;		     <0..MAX_PENS>    <if 2 XOR mode else draw>	
	; Returns:	None.
	; Description:  Colors pixel x,y to color indicated. If pen
	;		is in XOR mode, color is XOR of pen color and
	;		current background color of x,y.
	;---------------------------------------------------------------

	PUBLIC	GPLOT
GPLOT:
	;
	; Color pixel at point x,y to the color indicated in pen
	; (lsb). If the pen mode (msb) is 2, then the color to
	; plot is the logical exclusive or of the current color
	; and the pen color. (e.g. if gpoint(x,y) = 5 and a 
	; color = 3, the dot plotted is color 3 xor 5 = 6).
	; NOTE: All points are on the visible graphics screen.
	;
	push	b		; save bc
	lxi	h,4		; [bc] [ret] [x] [y] [pen] stacked
	dad	sp		; HL set up to obtain parameters
	mov	c,m		; get the x coordinate
	inx	h		;    in bc	
	mov	b,m		;
	inx	h		;
	mov	e,m		; get the y coordinate
	inx	h		;    in de
	mov	d,m		;
	lxi	h,8		; NOTE: Adjusting screen to middle
	dad	b		;     add 8 to every x coord
	mov	b,h		;
	mov	c,l		; 
	lxi	h,MSXBASE+mapxyc; calculate physical VDP address of point
	call	FASTMSX		; 
	lxi	h,8		; get penmode ! pencolor
	dad	sp		;
	mov	a,m		; get the pen color
	push	psw		;    and save 
	inx	h		; point to the pen mode	 
	mov	a,m		;
	cpi	2		; is the mode PX?
	jnz	noxor		;
	lxi	h,MSXBASE+readc	; read the current color
	call	FASTMSX		;
	pop	h		; get the current pen color in h
	xra	h		;    and xor with new color
	push	psw		;       and return to stack
noxor:
	pop	psw		; restore pen color
	lxi	h,MSXBASE+setatr; set the color 
	call	FASTMSX		;
	lxi	h,MSXBASE+setc	; write the pixel to specified color
	call	FASTMSX		;
	pop	b		; restore BC
	ret

	;---------------------------------------------------------------
	; GLINE
	;
	; Parameters:	x1,x2: integer, range: 0..XDOTS-1
	;		y1,y2: integer, range: 0..YDOTS-1
	;		pen: 2 bytes (integer):
	;		     LSB: pen color    MSB: pen drawing mode
	;		     <0..MAX_PENS>    <if 2 XOR mode else draw>	
	; Returns:	None.
	; Description:  Colors line x1,y2 -- x2,y2 to color indicated. 
	;		If pen is in XOR mode, color is XOR of pen color 
	;		and current background color of x,y.
	;---------------------------------------------------------------

	IF	USEGLINE	; Use 'C' dda.rel 
	PUBLIC	GLINE
GLINE:
	push	b	; save bc
	lxi	h,4	; [bc] [ret] [x1] [y1] [x2] [y2] [pen] stacked
	dad	sp	; HL set up to obtain parameters
	;
	; Plot line from point (x1,y1) to point (x2,y2) inclusive. 
	; 	NOTE:   All points are on the visible graphics screen.
	;
	;	NOTE: 	File dda.rel contains a gline routine based 
	;		solely upon gplot. This routine may not be
	;		optimal, but can serve for a first cut 
	;		implementation.
	;
	pop	b	;
	ret		;
	ENDIF

	;---------------------------------------------------------------
	; BG
	;
	; Parameters:	color: integer, range: 0..MAX_PENS
	; Returns:	None.
	; Description:  Sets all pixels in current background color to
	;		new color.
	;---------------------------------------------------------------

	PUBLIC	BG
BG: 
	;
	; Sets all pixels that are currently the bg color to the new
	; bg color
	;
	push	b		; Save BC register (if necessary)
	lxi	h,4		; [bc] [ret] [background] stacked
	dad	sp		; HL set up to obtain parameters
	mov	a,m		; get the background color to zap VDP
	sta	BAKCLR		; save background color for MSX
	mov	d,a		; 	and for bgclr	
	lxi	b,6144		; blast the whole thing
	lhld	GRPCOL		; get the address of the color plane
bgclr:
	mov	a,l		; set up VDP read
	di			; disasable ints 
	out	VDPCW		; send command
	mov	a,h		; get the high byte of address
	ani	03FH		; 
	out	VDPCW		; send command
	ei			; make interrupts happen again   
	xthl			; waste some time . . . . 
	xthl			;
	in	VDPDR		; read from VDP
	ani	0F0H		; keep the forground color intact
	ora	d		; merge in the new bg color
	mov	e,a		; save the color byte
	mov	a,l		; set up VDP write
	di			; disasable ints 
	out	VDPCW		; send command
	mov	a,h		; get the high byte of address
	ani	03FH		; 
	ori	040H		;
	out	VDPCW		; send command
	ei			; make interrupts happen again   
	xthl			; waste some time . . . .
	xthl 
	mov	a,e		; restore color byte
	out	VDPDW		; write back out
	inx	h		; bump to next byte
	dcx	b		;
	mov	a,b		; test if done
	ora	c		;
	jnz	bgclr		;

	pop	b		; restore b
	ret

	;---------------------------------------------------------------
	; GWIPE
	;
	; Parameters:	color: integer, range: 0..MAX_PENS
	;		bot:   integer, range: -1..YDOTS-1 
	; Returns:	None.
	; Description:  Clears all pixels lines 0..bot to color.
	;		If bot = -1, do nothing.
	;---------------------------------------------------------------

	PUBLIC  GWIPE
GWIPE:
	;
	; Clear screen from (0,0) to (xdots-1,bot) to the background
	; color. Usually bot is ydots-1; but, the value may be < ydots-1
	; if DUALSCR = 0 and in SPLITMODE.
	;
 	push	b		; Save BC register (if necessary)
	lxi	h,6		; [bc] [ret] [background] [bot] stacked
	dad	sp		; HL set up to obtain parameters
				; NOTE: In this version, ignore bg color 
	mov	a,m		; get bottom of screen clear
	inr	a		; test if nothing to clear
	jz	gwipe1		; 
	
	mov	l,a		; bot is in terms of pixels
	mvi	h,0		; Must mult by 32 to get # byte to clear
	dad	h		;    multiply by 32
	dad	h		;
	dad	h		;
	dad	h		;
	dad	h		;
  	mov	b,h		; we now have # of bytes to clear (max 6144)
	mov	c,l		; copy to hl
	xra	a		; clear to zeros
	lhld	GRPCGP		; base of VDP pixel buffer (use global var)
	push	h		; save temporarily
	lxi	h,MSXBASE+filvrm; fill dat der memory
	xthl			; restore MSX parm in hl 
	call	FULLMSX		; use MSX call that preserves all regs!
	pop	h		; 
gwipe1:
	pop	b		; restore bc
	ret

;************************************************************************
;								       	*
;		SECTION: Miscellaneous Routines       	       		*
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; BEEP
	;
	; Parameters:	None.
	; Returns:	None.
	; Description:  Outputs audible beep
	;---------------------------------------------------------------

	PUBLIC 	BEEP
BEEP:
	push	b	; save bc register (if necessary)
        mvi     a,ctrlg
        call    bios4
	;
	; Sound computer bell (Usually XCONOU(7))
	; Do not advance cursor
	;
	pop	b	; restore
	ret


	;---------------------------------------------------------------
	; TOPOFM
	;
	; Parameters:	None.
	; Returns:	HL := highest address of TPA
	; Description:  Defines end of memory space
	;---------------------------------------------------------------

	PUBLIC	TOPOFM
TOPOFM:
	lhld	6	; get address of end of TPA from Base Page 
	ret		;   BDOS jump (note Z flag may be undefined)
 
;************************************************************************
;								        *
;		SECTION: FILL & DOTC Support		       		*
;		   ***** <OPTIONAL> *****			        *
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; GPOINT
	;
	; Parameters:	x: integer, range: 0..XDOTS-1
	;		y: integer, range: 0..YDOTS-1
	; Returns:	HL:= Color of pixel x,y
	;---------------------------------------------------------------

	PUBLIC 	GPOINT
GPOINT: 
	push	b	; Save BC register (if necessary)
	lxi	h,4	; [bc] [ret] [x] [y] stacked
	dad	sp	; HL set up to obtain parameters
	;
	; Returns color of pixel x,y.
	; x,y guaranteed on the visible screen.
	;
 	pop	b	; restore BC
	ret


;************************************************************************
;								        *
;		SECTION: Printer Interface		       		*
;		  ***** <OPTIONAL> *****			        *
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; PRTREA
	;
	; Parameters:	None
	; Returns:	printer status in HL: zero    -> printer busy
	;			    	      nonzero -> printer ready
	;---------------------------------------------------------------

	PUBLIC	PRTREA
PRTREA:
	push	b	; Must save BC register
;	lxi	h,15	; Usually bios(15) call
;	push	h	; set up call parameter
;	call	bios	; Get printer status (status in HL)  
;	pop	d	; Discard parameter
	pop	b	; restore BC
	ret

	;---------------------------------------------------------------
	; PRTCHA
	;
	; Parameters:	ch: char, range: 0..255
	; Returns:	None.
	; Description:  Output character to printer
	;---------------------------------------------------------------

	IF	FALSE
	PUBLIC	PRTCHA
PRTCHA:
	push	b	; Must save BC register
	lxi	h,4	; index char in stack [BC] [ret] [ch]
	dad	sp	; get character in de
	mov	e,m	; .
	inx	h	;   .
	mov	d,m	;     .
;	push	d	; push character
;	lxi	h,5	; Usually, a bios(5,ch) call is performed
;	push	h	; push bios vector number
;	call	bios	; send character to printer
;	pop	d	; remove parameters
;	pop	d	; .
	pop	b	; restore bc
	ret
	ENDIF

;************************************************************************
;								        *
;		SECTION: Joystick Interface		       		*
;		  ***** <OPTIONAL> *****			        *
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; JOYIN
	;
	; Parameters:	joy#: integer, range: 0..MAX_PADDLES
	; Returns:	integer indicating paddle position
	;		NOTE: value system dependent (see guide)
	;---------------------------------------------------------------

	PUBLIC	JOYIN
JOYIN:
	push	b	; save BC (if necessary)
	lxi	h,4	; index char in stack [BC] [ret] [n]
	dad	sp	; pointer to n (which joystick to access)
	;
	; Return in HL the input from joystick n -- Return values are 
	; defined in customization guide.
	;
	pop	b	; restore BC
	ret


	;---------------------------------------------------------------
	; BUTTON	
	;
	; Parameters:	joy#: integer, range: 0..MAX_PADDLES
	; Returns:	HL: -> 0,       if joystick button not pushed
	;		    -> nonzero, if joystick button pushed
	;---------------------------------------------------------------

	PUBLIC	BUTTON
BUTTON:
	push	b	; save BC (if necessary)
	lxi	h,4	; index char in stack [BC] [ret] [n]
	dad	sp	; pointer to n (which joystick to access)
	;
	; Return TRUE if button on joystick n has been pressed, else
	; return FALSE. (Note: HL := 1 for true and HL := 0 for FALSE)
	;
	pop	b	; restore BC
	ret

;************************************************************************
;								        *
;		SECTION: Palette Interface	       			*
;		  ***** <OPTIONAL> *****			        *
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; SETPL	
	;
	; Parameters:	pal#: integer, range 0..MAX_PENS
	;		r,g,b: integers, range 0..MAX_COLOR 
	; Returns:	None.
	; Description:	Sets palette to red, green, blue levels provided.
	;---------------------------------------------------------------

	PUBLIC	SETPL
SETPL:
	push	b	; Save BC (if necessary)
	lxi	h,4	; stack [BC] [ret] [n] [r] [g] [b]
	dad	sp	; pointer to n and rgb values
	;
	; Palette number 'n' is set to the RGB value r,g,b.
	; The number of palettes and the rgb ranges are defined in 
	; in the customization module. (see implementation guide)
	;
	pop	b	; restore bc
	ret

	;---------------------------------------------------------------
	; PAL	
	;
	; Parameters:	pal#: integer, range 0..MAX_PENS
	; Returns:	HL := POINTER to array of three integers (r,g,b)
	; Description:	Return palettes' RGB numbers
	;---------------------------------------------------------------

	PUBLIC	PAL
PAL:
	push	b	; Save BC (if necessary)
	lxi	h,4	; stack [BC] [ret] [n] 
	dad	sp	; pointer to n and rgb values
	;
	; Return vector of the RGB values for palette 'n'.
	; HL points to a vector of three integers, r being first and
	; b being last. Usually, palette 0 is the background color.  
	; The number of palettes and the rgb ranges are defined in 
	; in the customization module. (see implementation guide)
	;
	pop	b	; restore bc
	ret


;************************************************************************
;								        *
;		SECTION: Tones (sound) Interface	       		*
;		     ***** <OPTIONAL> *****			        *
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; TONES	
	;
	; Parameters:	freq: level  of sound; integer, range 0..MAX_TONE
	;               duration: how long sound lasts; positive integer 
	; Returns:	None.
	;---------------------------------------------------------------

	PUBLIC	TONES
TONES:
	push	b	; save BC (if necessary)
	lxi	h,4	; stack [BC] [ret] [index] [duration]
	dad	sp	; pointer to index
	;
	; Make the sound generator produce a sound of index value 
	; (note: index is usually the frequency in HZ) of duration
	; length (duration is always specified in units of 1/60 sec.)
	; Also note that an index of 0 produces silence (for wait).
	;
	pop	b	; restore BC
	ret

;************************************************************************
;								        *
;		SECTION: Picture File Interface	       			*
;		     ***** <OPTIONAL> *****			        *
;								       	*
;************************************************************************

	;---------------------------------------------------------------
	; GETGRF	
	;
	; Parameters:	buffaddr: address of 128 byte buffer; 16-bit addr
	;               secnum:   current sector # being read; integer 
	;			  RANGE: 0..MAX_SECTOR		
	; Returns:	boolean;  0 if done, 1 if data loaded into buffer 
	;---------------------------------------------------------------

	PUBLIC	GETGRF
GETGRF:
	push	b	; save BC (if necessary)
	lxi	h,4	; stack [BC] [ret] [buffaddr] [secnum]
	dad	sp	; pointer to buffaddr
	;
	; Loads the next "chunk" (128 bytes) of graphics memory to store 
	; on disk. Buffaddr is the address to store the grahics data.
	; The first chunk is denoted as secnum 0. GETGRF returns
	; a non-zero value in HL if something was placed in the buffer.
	; A zero (FALSE) value is returned when all data for the graphics
	; memory is transferred. Note that a "header" sector can be put 
	; into the buffer for additional security. 
	;
	pop	b	; restore BC
	ret

	;---------------------------------------------------------------
	; PUTGRF	
	;
	; Parameters:	buffaddr: address of 128 byte buffer; 16-bit addr
	;               secnum:   current sector # of file to write to
	;			          graphics area; integer 
	;			  RANGE:  0..MAX_SECTOR		
	; Returns:	boolean;  0 if done or error, 1 operation OK
	;---------------------------------------------------------------

	PUBLIC	PUTGRF
PUTGRF:
	push	b	; save BC (if necessary)
	lxi	h,4	; stack [BC] [ret] [buffaddr] [secnum]
	dad	sp	; pointer to buffaddr
	;
	; Loads the next "chunk" (128 bytes) of a picture file (pointed at 
	; by buffaddr) into the graphics screen/memory (1st chunk is # 0). 
	; A  zero (FALSE) value is returned if enough data has been
	; received or an error has been detected (e.g. a header is saved
	; in the picture file).  It is up to the OEM to determine the
	; contents of the picture file. The number of sectors in the file
	; is determined by the number saved in the PUTGRF operation.
	;
	pop	b	; restore BC
	ret

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

	;---------------------------------------------------------------
	;
	;	Control Key Table
	;
	;	Purpose: Allows customization of the control keys used
	;		 by Logo for editing, switching screens, and
	;		 breaking interpreter. Note that the standard
	;		 Logo definition uses the low 28 control 
	;		 functions of the ASCII standard. Non-printing
	;		 characters can be made illegal by including 
	;		 their values at the end of the table (after
	;		 the standard definitions). 
	;	Structure:
	;		 Each control character position is placed with 
	;		 the corresponding function. (e.g. the character
	;		 to end the Logo screen editor must be the 3rd
	;		 entry in the table. The table is terminated by
	;		 a zero entry.
	;		  
	;----------------------------------------------------------------

	COMMON	/CTLCH/

	db	1 	; -1 beginning of line			
	db	2  	; -2 back one space (non-destructive)	
	db	3  	; -3 end Logo screen editor		
	db	4  	; -4 erase char at cursor		
	db	5  	; -5 to end of current line		
	db	6  	; -6 forward one space			
	db	7  	; -7 immediate throw to top level	
	db	8	; -8 back one character (destructive)	
	db	9  	; -9 tab '\t' 				
	db	10 	; -10 line feed			
	db	11 	; -11 erase from cursor to end of line	
	db	12 	; -12 current line to center		
	db	13 	; -13 carriage return			
	db	14  	; -14 down one text line
	db	15  	; -15 open a new text line		
	db	16    	; -16 up one text line			
	db	17  	; -17 insert "\" character		
	db	18  	; -18 top of edit buffer 		
	db	19  	; -19 split screen mode		
	db	20  	; -20 text mode			
	db	21  	; -21 up one text page			
	db	22  	; -22 down one page of text		
	db	23  	; -23 wait (until another key pressed)	
	db	24   	; -24 bottom of edit buffer 		
	db	25  	; -25 recall last line (kill buffer)	
	db	26 	; -26 pause function			
	db	127 	; -27 alternate destructive backspace	
	db 	0	; >>> end of character table <<<	

	;--------------------------------------------------------------
	;					         t2		
	;	DRAW_TURTLE:			         ^		
<EFBFBD>	;					        / \		
	;    	The  Logo "turtle draw" routine	       /   \		
	;	uses 4 lines defined by the           /  .  \		
	;	vertices t0..t3. The turtle is	     / ' p ` \ 		
	;	drawn in XOR mode to permit	   t3         t1	
	;	simple erasing. Note that the				
	;	offset table below uses the            TURTLE		
	;       default (most common) aspect ratio. (p = turtle pos)
	;
	;		
	;--------------------------------------------------------------

	COMMON	/TURTBL/

	; aspect ratio 19/24, xdots = 320  ydots = 200
	
	;	t1_x	t1_y	t2_x	t2_y	t3_x	t3_y	degrees
	;	----	----	----	----	----	----	-------
	db	   5,	   3,	   0,	  -8,     -5,	   3	;    0
	db	   5,	   3,	   1,	  -8,     -5,	   3	;    6	
	db	   4,	   4,	   2,	  -8,     -6,	   2	;   12
	db	   4,	   4,	   3,	  -8,     -6,	   2	;   18
	db	   3,	   4,	   4,	  -7,     -6,	   1	;   24
	db	   2,	   5,	   5,	  -7,     -6,	   1	;   30
	db	   2,	   5,	   6,	  -6,     -6,	   0	;   36
	db	   1,	   5,	   7,	  -6,     -6,	   0	;   42
	db	   1,	   5,	   8,	  -5,     -6,	  -1	;   48
	db	   0,	   5,	   8,	  -5,     -6,	  -1	;   54
	db	  -1,	   5,	   9,	  -4,     -6,	  -2	;   60
	db	  -1,	   5,	   9,	  -3,     -6,	  -2	;   66
	db	  -2,	   5,	  10,	  -2,     -5,	  -3	;   72
	db	  -3,	   5,	  10,	  -2,     -4,	  -3	;   78
	db	  -3,	   4,	  10,	  -1,     -4,	  -4	;   84	
	db	  -4,	   4,	  10,	   0,     -4,	  -4	;   90


	;---------------------------------------------------------------
	;
	;	Logo Parameter Definitions
	;	
	;	Purpose: Defines implementation dependent values such as
	;		 screen size, number of pen colors, defaults, 
	;		 and hardware options.
	;
	;	Structure:
	;
	;	PARAMS:	 DW	xx	; parameter 1
	;		 DW	yy	; parameter 2
	;
	;	Each parameter is a 16-bit word value 	
	;
	;----------------------------------------------------------------

	COMMON	/PARAMS/

<EFBFBD>	dw	24	; SCRROWS   -- # of text rows			
	dw	38      ; SCRCOLS   -- # of text columns		
	dw	24	; GRAFROWS  -- # of graphic text rows 		
	dw	29	; GRAFCOLS  -- # of graph text columns		
	dw	21	; SCRSPLT   -- Default SS row: 0<#<=GRAFCOLS	
	dw	15	; INIT_PEN  -- Default pen color: 0<=#<=MAXPEN	
	dw	 4	; INIT_BG   -- Default backgound color		
	dw	 4	; TABSIZE   -- Tab stop number 		
	dw	15	; MAX_PENS  -- Max # of palette/pen indexes	
	dw	00	; MAX_COLOR -- highest color index value	
	dw   10000	; MAX_TONE  -- highest tone index		
	dw	-1	; MAX_PADDLE-- number of paddles - 1		
	dw     240	; XDOTS     -- pixels in x coordinate		
	dw     192	; YDOTS     -- pixels in y coordinate
	dw	 8      ; FNSIZE    -- # characters in file name	
	dw     	 2	; MAX_ASPECT-- 1/# <= aspect_ratio <= #	
	dw	 0	; TWOSCR    -- Separate text/graphic screen	
			;		1 = yes  0 = no			
	dw	15	; MAX_BG    -- maximum background color index  
	dw	24	; MAX_SPLIT -- maximum number of split lines	
			;	        1 <= # <= GRAFROWS		
	dw	10	; XRATIO    -- x/y aspect ratio (of a PIXEL)
	dw	 8	; YRATIO    --     y of above 		 	

	;---------------------------------------------------------------
	;
	;	Text Message Table	
	;	------------------
	;
	;	Purpose: Allows customization of Logo messages to fit
	;		 specific implementations.
	;
	;	Structure:
	;
	;	LTEXT:	mess1 ; address of string1
	;		mess2 ; address of string2
	;		 .
	;		messn ; address of stringn
	;	
	;	string1: 0 or more charactered terminated by a zero byte
	;	
	;----------------------------------------------------------------

	COMMON	/LTEXT/	

	dw	mess1
	dw	mess2
	dw	mess3

	DSEG
	; SIGNON  -- Custom signon message: 1 <= length < SCRCOLS	
mess1:	db	'CP/M MSX Dr. Logo, Version: **BETA**',0

	; EDITMSG -- Edit file message:     1 <= length < SCRCOLS 
mess2:	db	'Log<6F> Editor<6F> ^C to accept<70> ^G to quit',0
<EFBFBD>
	; BAR_CH  -- Line character
mess3:	db	'_'

	END