Emblem.asm

#include "ti86asm.inc"

; ===========================
; Emblem 86 version 1.1 gamma
; ===========================
; Mark's new label

; This is an 86 assembly program that allows users to draw a custom emblem for
; their calculators (on-calc) and install it in a user-interrupt routine so that
; it will be constantly present in the upper-right corners of their screens.
; See the readme file for more information.

; By Mark Shroyer, 12.16.1999.
; [email protected]  http://gael.port5.com/


.org _asm_exec_ram

false					.equ	$00	; Macro defines for use in my program.
true					.equ	$01

graphmem				.equ	$FC00	; The beginning of the screen memory.

_user_int_checksum		.equ	$D2FD	; Where user int checksum is stored.
_user_int_routine		.equ	$D2FE	; Where routine memory starts.


	nop
	jp Prog_Initiate
	.dw 0
	.dw FileID

FileID:
	.db "Emblem 86 v1.1",Lgamma,0


; =====

; Volatile data:
; This data is intented to possibly change throughout program execution.

Data_IntEnabled:
; Specifies whether the user interrupt flag was set at the beginning of
; program execution so that the closing routine knows whether to re-enable it
; upon termination of the program.  This value may also be reset if the user
; tells the program to enable or disable the user-int routine.
	.db false

Data_MainMenu_02:
	.db " 3. Enable user-int  ",0

Data_Icon:
	.db %10000000, %00000000, %00000000
	.db %10000000, %01010010, %01100101
	.db %11001010, %01110101, %01010110
	.db %10101010, %01010111, %01100101
	.db %11000100, %01010101, %01010101
	.db %00011000, %00000000, %00000000
	.db %00000000, %00110011, %00000000
	.db %00000000, %11001100, %10000000
	.db %00000000, %00000000, %00000000
	.db %00000000, %10001100, %00000000
	.db %00000000, %01001100, %00000000
	.db %00000000, %00000000, %00000000
	.db %00000001, %00000100, %00000000
	.db %00000000, %10001000, %00000000
	.db %00000000, %01110000, %00000000
	.db %00000000, %00000000, %00000000



; =====

; Static data:
; This data is not supposed to change.

Data_MainMenu_Title:
	.db 222," Emblem 86    v1.1",Lgamma," ",0

Data_MainMenu_01:
	.db " 1. Veiw/change icon "
	.db " 2. Install routine  ",0

Data_MainMenu_03:
	.db "Press MORE for info. ",0

Data_Toggle_Enable:
	.db " 3. Enable user-int  ",0

Data_Toggle_Disable:
	.db " 3. Disable user-int ",0

Data_Default_Icon:
	.db %10000000, %00000000, %00000000
	.db %10000000, %01010010, %01100101
	.db %11001010, %01110101, %01010110
	.db %10101010, %01010111, %01100101
	.db %11000100, %01010101, %01010101
	.db %00011000, %00000000, %00000000
	.db %00000000, %00110011, %00000000
	.db %00000000, %11001100, %10000000
	.db %00000000, %00000000, %00000000
	.db %00000000, %10001100, %00000000
	.db %00000000, %01001100, %00000000
	.db %00000000, %00000000, %00000000
	.db %00000001, %00000100, %00000000
	.db %00000000, %10001000, %00000000
	.db %00000000, %01110000, %00000000
	.db %00000000, %00000000, %00000000

Data_Icon_Frame:
	.db %00000011, %11111111, %11111111, %11111111, %11000000
	.db %00000010, %00000000, %00000000, %00000000, %01000000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000010, %00000000, %00000000, %00000000, %01110000
	.db %00000011, %11111111, %11111111, %11111111, %11110000
	.db %00000000, %11111111, %11111111, %11111111, %11110000
	.db %00000000, %11111111, %11111111, %11111111, %11110000

Data_Editor_01:
	.db "1. Edit icon",0
Data_Editor_02:
	.db "2. Clear icon",0
Data_Editor_03:
	.db "3. Reload current",0
Data_Editor_04:
	.db "4. Restore default",0

Data_Instructions_01:
	.db "ENTER = Set pixel",0
Data_Instructions_02:
	.db "DEL = Cear pixel",0

Data_About:
	.db "Mark Shroyer         "
	.db "[email protected]  "
	.db "                     "
	.db "12.16.1999           "
	.db "v1.1",Lgamma,"                 ",0

Data_DoneMsg:
	.db "Done!",0

; =====

; Program routines:
; This is the program itself.


Prog_Initiate:
	ei								; Make sure that interrupts are enabled...
	res indicRun,(iy+indicflags)	; Rid of that nasty running indicator.
	res appAutoScroll,(iy+appflags)	; Turn off auto-scrolling text
	res appTextSave,(iy+appflags)	; Deactivate writing to the text shadow.
	ld hl,Data_IntEnabled	; \
	ld (hl),false			;  \
	bit 2,(iy+$23)			;   \ Save the condition of the user-interrupt
	jr z,Prog_Initiate_01	;   / flag and then clear it.
	res 2,(iy+$23)			;  /
	ld (hl),true			; /
Prog_Initiate_01:
	call _flushallmenus	; Clear the remnants of any menus that were up before
						; the program was run (if they aren't cleared, the
						; calculator will make text scroll vertically when it
						; reaches a certain point, because it still thinks that
						; menus are up and doesn't want to overwrite them.
	call _homeup	; Return text cursor the the upper-left of the screen.

; -----

Prog_MainMenu:
	call _clrScrn			; Clear the screen memory and the text shadow.
	call Prog_PrepToggle
	call Prog_MenuTopBar
	call _newline			; Execute a carriage-return
	ld hl,Data_MainMenu_01	; \ Print the first line
	call _puts				; / of the menu.
Prog_MainMenu_01:
	ld a,0
	ld (_curCol),a
	ld a,4
	ld (_curRow),a
	ld hl,Data_MainMenu_02
	call _puts
	call _newline
	ld hl,Data_MainMenu_03
	call _puts

Prog_MainMenu_02:
	call _getkey
	cp k1
	jp z,Prog_IconViewer
	cp k2
	jp z,Prog_Install_Routine
	cp k3
	jp z,Prog_ToggleInt
	cp kNext
	jp z,About
	cp kExit
	jp z,Prog_Terminate
	jr Prog_MainMenu_02

; -----

About:
; Brings up the "About" screen, in all its glory....
	call _clrScrn
	call Prog_MenuTopBar
	call _newline
	ld hl,Data_About
	call _puts
	call _getkey
	call _clrScrn
	jp Prog_MainMenu

; -----

Prog_ToggleInt:
; Toggles the state of the Data_IntEnabled variable (which tells the termination
; routine whether to set the user-int flag or not when the program ends), then
; jumps to a certain point on the menu routine.  This can be done because this
; menu routine is really the only thing that calls this function.
	ld a,(Data_IntEnabled)	; \
	cp true					;  \
	jr nz,Prog_ToggleInt_01	;   \
	ld a,false				;    \  Toggle the state of the data flag I put
	ld (Data_IntEnabled),a	;     > at Data_IntEnabled.
	jr Prog_ToggleInt_02	;    /
Prog_ToggleInt_01:			;   /
	ld a,true				;  /
	ld (Data_IntEnabled),a	; /

Prog_ToggleInt_02:   		; Prog_PrepToggle is called to change the state
	call Prog_PrepToggle	; of the text that is displayed on the main menu
							; to advertise this function.  See Prog_PrepToggle
							; itself for more details about this.
	jp Prog_MainMenu_01	; Jump back to just the right point on the menu routine...

; -----

Prog_PrepToggle:
; Using the data about the state of the user-int flag before program execution
; (currently stored at Data_IntEnabled), this routine switches around the text
; for line 3 of the main menu, so that always displays the appropriate command:
; either "Enable user-int" or "Disable user-int", respective to the current
; state of things.
	ld a,(Data_IntEnabled)
	cp true
	jr nz,Prog_PrepToggle_01

	ld hl,Data_Toggle_Disable
	ld de,Data_MainMenu_02
	ld bc,22
	ldir
	ret
Prog_PrepToggle_01:
	ld hl,Data_Toggle_Enable
	ld de,Data_MainMenu_02
	ld bc,22
	ldir
	ret

; -----

Prog_MenuTopBar:
; Simple function, draws in the title line that you see on the main menu and a
; few other screens throughout the program.	
	call _homeup
	set textInverse,(iy+textflags)
	ld hl,Data_MainMenu_Title
	call _puts
	res textInverse,(iy+textflags)
	ret

; -----

Prog_IconViewer:
; This is the routine that causes and monitors the menu that first comes up
; when one selects option 1 on the main menu.
	call _clrScrn
	call _homeup
	call Prog_MenuTopBar
Prog_IconViewer_s:
	call Prog_IconEdit_Refresh
	ld hl,_penCol
	ld (hl),5
	ld hl,_penRow
	ld (hl),15
	ld hl,Data_Editor_01
	call _vputs
	ld hl,_penCol
	ld (hl),5
	ld hl,_penRow
	ld (hl),23
	ld hl,Data_Editor_02
	call _vputs
	ld hl,_penCol
	ld (hl),5
	ld hl,_penRow
	ld (hl),31
	ld hl,Data_Editor_03
	call _vputs
	ld hl,_penCol
	ld (hl),5
	ld hl,_penRow
	ld (hl),39
	ld hl,Data_Editor_04
	call _vputs
Prog_IconViewer_01:
	call _getkey
	cp k1
	jr nz,Prog_Icon_Viewer_02
Prog_IconViewer_01b:
	call _clrScrn
	call _homeup
	call Prog_MenuTopBar
	ld hl,_penCol
	ld (hl),5
	ld hl,_penRow
	ld (hl),15
	ld hl,Data_Instructions_01
	call _vputs
	ld hl,_penCol
	ld (hl),5
	ld hl,_penRow
	ld (hl),23
	ld hl,Data_Instructions_02
	call _vputs
	jp Prog_ChangeIcon
Prog_Icon_Viewer_02:
	cp kEnter
	jr z,Prog_IconViewer_01b	; Jump to the same place that k1 would have
								; brought you.
	cp k2
	jp z,Prog_ClearIcon
	cp k3
	jp z,Prog_RestoreCurrent
	cp k4
	jp z,Prog_RestoreDefault
	cp kExit
	jp z,Prog_MainMenu
	jr Prog_IconViewer_01

; -----

Prog_ClearIcon:
; Clears the entire icon.
	ld hl,Data_Icon
	ld (hl),0
	ld de,Data_Icon+1
	ld bc,47
	ldir
	jp Prog_IconViewer_s

; -----

Prog_RestoreDefault:
; Copies 48 bytes from Data_Default_Icon to Data_Icon, restoring the default
; sprite.
	ld hl,Data_Default_Icon
	ld de,Data_Icon
	ld bc,48
	ldir
	jp Prog_IconViewer_s

; -----

Prog_RestoreCurrent:
; Copies 48 bytes from Icon (which is located in the user-interrupt routine)
; to Data_Icon, taking any installed icon into the program.  The user interrupt
; routine does not need to be activated for this to work.  If there is something
; besides one of these icons in that space in memory (or nothing at all), this
; will either result in a blank icon or a bunch of garbage, but no harm will be
; done.
	ld hl,Icon
	ld de,Data_Icon
	ld bc,48
	ldir
	jp Prog_IconViewer_s

; -----

Prog_IconEdit_Refresh:
; Refreshes the image of the sprite Data_Icon and the sprite frame that it is
; overlayed on.
	ld hl,Data_Icon_Frame
	ld de,graphmem+282
	ld b,22
Prog_IconEdit_Refresh_01:
	push bc
	ld bc,5
	ldir
	ex de,hl
	push de
	ld de,11
	add hl,de
	pop de
	ex de,hl
	pop bc
	djnz Prog_IconEdit_Refresh_01

	ld hl,Data_Icon
	ld de,graphmem+315
	ld b,16
Prog_IconEdit_Refresh_02:
	push bc
	ld bc,3
	ldir
	ex de,hl
	push de
	ld de,13
	add hl,de
	pop de
	ex de,hl
	pop bc
	djnz Prog_IconEdit_Refresh_02
	ret

; -----

Prog_IconEdit_ChangeBit:
; Sets or clears specific bit in Data_Icon.  The bit to be modified is
; determined by treating the sprite Data_Icon as a matrix of points, counted
; from the top-left pixel (i.e. bit) using (_penCol) as the abscissa (x
; coordinate) and using (_penRow) as the ordinate (y coordinate).  If bit 0 of
; asm_flag1 is set then the bit will be set; otherwise, the bit will be zeroed.
; This routine is based on the same principle as my Set_Pixel function.
	ld hl,_penCol
	ld b,(hl)		; Load the abscissa into b.
	ld hl,_penRow
	ld c,(hl)	; Load the ordinate into c.
	push bc		; Push the word-register bc onto the stack.
	ld hl,0		; Clear hl so that h can be used as a counter variable.
Prog_IconEdit_ChangeBit_01:
	ld a,b							; \  Jump to Prog_IconEdit_ChangeBit_02
	cp 8							;  > if b, the abscissa, is less than 8.
	jr c,Prog_IconEdit_ChangeBit_02	; /
	sub 8	; \  Subtract 8 from b (whose value is currently stored in a), load
	ld b,a	;  > the new value back to b, and increment h.
	inc h	; /
	jr Prog_IconEdit_ChangeBit_01	; Loop back to ..._01 to do it again until
						; b == mod((abscissa),8) and h == (abscissa)-b.

; From here on in this routine, the following notations may be used:
;	(x-whole) =		The value of the greatest multiple of 8 less than or equal
;					to the value of the abscissa.
;	(x-remainder) =	The value of mod((abscissa),8)
;	(y-offset)/3 =	One-third of the byte offset that needs to be added to the
;					address of Data_Icon to locate the right byte row (this
;					expression is equal to the ordinate).
;	(y-offset) =	Three times the ordinate.
;	(offset) =		The total offset from Data_Icon that will be used to locate
;					the byte that the pixel in question is located in.

Prog_IconEdit_ChangeBit_02:
	ld l,b		; h = (x-whole)
				; l = (x-remainder)
				; c = (y-offset)/3

	ex de,hl	; d = (x-whole)
				; e = (x-remainder)
				; c = (y-offset)/3
	ld hl,Data_Icon		; Initiate the value of (hl), so that the offset can be
						; added to it to obtain the address of the byte the
						; specific pixel is in.
	ld b,0
	ld a,c		; a = (y-offset)/3
	ld c,d		; c = (x-whole)
	add hl,bc	; Add (x-whole) to hl (increasing the offset).
	ld c,e	; c = (x-remainder)
	ld de,0	; Zero de so that it can be used as an element in the addition.
	ld e,a	; e = (y-offset)/3  (Note that this also sets de to the same value).
	ld b,3	; Load b (the counter variable for the djnz looping operation) with
			; three, so that the following loop will be repeated three times:
Prog_IconEdit_ChangeBit_03:
	add hl,de	; Add (y-offset)/3 to the running offset total (since this will
				; be done three times, it will really be adding (y-offset) to
				; the running total).
	djnz Prog_IconEdit_ChangeBit_03	; Decrement b and jump back to ..._03 so
									; long as b is greater than 0.

	ld a,c	; a = (x-remainder)
	pop bc		; Restore bc from the stack.
	cp 0	; Compare (x-remainder) to zero.
		jr nz,Prog_IconEdit_ChangeBit_04	; If not equal, jump to ..._04.
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_03b
		set 7,(hl)	; Set the bit (7) and exit routine of bit 0 of asm_flag1
					; is set.
		ret			; Done.
Prog_IconEdit_ChangeBit_03b:
		res 7,(hl)	; Reset the bit (7) and exit the routine, done if bit 0
		ret			; of asm_flag1 is not set.
Prog_IconEdit_ChangeBit_04:		; The same deal, this time testing for bit 6...
	cp 1
		jr nz,Prog_IconEdit_ChangeBit_05
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_04b
		set 6,(hl)
		ret
Prog_IconEdit_ChangeBit_04b:
		res 6,(hl)
		ret
Prog_IconEdit_ChangeBit_05:
	cp 2
		jr nz,Prog_IconEdit_ChangeBit_06
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_05b
		set 5,(hl)
		ret
Prog_IconEdit_ChangeBit_05b:
		res 5,(hl)
		ret
Prog_IconEdit_ChangeBit_06:
	cp 3
		jr nz,Prog_IconEdit_ChangeBit_07
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_06b
		set 4,(hl)
		ret
Prog_IconEdit_ChangeBit_06b:
		res 4,(hl)
		ret
Prog_IconEdit_ChangeBit_07:
	cp 4
		jr nz,Prog_IconEdit_ChangeBit_08
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_07b
		set 3,(hl)
		ret
Prog_IconEdit_ChangeBit_07b:
		res 3,(hl)
		ret
Prog_IconEdit_ChangeBit_08:
	cp 5
		jr nz,Prog_IconEdit_ChangeBit_09
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_08b
		set 2,(hl)
		ret
Prog_IconEdit_ChangeBit_08b:
		res 2,(hl)
		ret
Prog_IconEdit_ChangeBit_09:
	cp 6
		jr nz,Prog_IconEdit_ChangeBit_10
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_09b
		set 1,(hl)
		ret
Prog_IconEdit_ChangeBit_09b:
		res 1,(hl)
		ret
Prog_IconEdit_ChangeBit_10:
		bit 0,(iy+asm_flag1)
		jr z,Prog_IconEdit_ChangeBit_10b
		set 0,(hl)
		ret
Prog_IconEdit_ChangeBit_10b:
		res 0,(hl)
		ret

; -----


Prog_ChangeIcon:
; This is the input loop for the icon editing.  It checks for the following
; keypresses:
;	- up
;	- down
;	- left
;	- right
;	- enter
;	- delete
;	- exit

	ld hl,_penCol	; \
	ld (hl),0		;  \ Zero the coordinates of the cursor so that it starts in
	ld hl,_penRow	;  / the upper-left corner of the editing window.
	ld (hl),0		; /
Prog_ChangeIcon_01:
	call Prog_IconEdit_Refresh	; Redraw the icon.

	ld a,(_penCol)			; \
	cp 24					; |
	jr c,Prog_ChangeIcon_02	; |
		ld a,23				; |
		ld (_penCol),a		; |	Checks for clipping in the
Prog_ChangeIcon_02:			; |	coordinate values stored in
	ld a,(_penRow)			; >	the variables _penCol and
	cp 16					; |	_penRow for the coordinates
	jr c,Prog_ChangeIcon_03	; |	of the edit box cursor.
		ld a,15				; |
		ld (_penRow),a		; |
Prog_ChangeIcon_03:			; /

	ld a,(_penCol)			; \		Add the appropriate offesets to
	add a,88				;  \	the edit-box coordinates of the
	ld b,a					;   \	cursor and store those values
	ld a,(_penRow)			;    >	in the b and c registers
	add a,19				;   /	so that the cursor can be drawn
	ld c,a					;  /	at screen position ( b,c ) by
	call Prog_DrawCursor	; /		the Prog_DrawCursor routine.

	call _getkey
	cp kUp
	jr nz,Prog_ChangeIcon_11
	ld hl,_penRow
	ld a,(hl)
	cp 0
	jr z,Prog_ChangeIcon_01
	dec (hl)
	jr Prog_ChangeIcon_01
Prog_ChangeIcon_11:
	cp kDown
	jr nz,Prog_ChangeIcon_12
	ld hl,_penRow
	inc (hl)
Prog_ChangeIcon_12:
	cp kLeft
	jr nz,Prog_ChangeIcon_13
	ld hl,_penCol
	ld a,(hl)
	cp 0
	jr z,Prog_ChangeIcon_01
	dec (hl)
	jr Prog_ChangeIcon_01
Prog_ChangeIcon_13:
	cp kRight
	jr nz,Prog_ChangeIcon_14
	ld hl,_penCol
	inc (hl)
Prog_ChangeIcon_14:
	cp kEnter
	jr nz,Prog_ChangeIcon_15
	set 0,(iy+asm_flag1)
	call Prog_IconEdit_ChangeBit
	jr Prog_ChangeIcon_01
Prog_ChangeIcon_15:
	cp kDel
	jr nz,Prog_ChangeIcon_16
	res 0,(iy+asm_flag1)
	call Prog_IconEdit_ChangeBit
	jr Prog_ChangeIcon_01
Prog_ChangeIcon_16:
	cp kExit
	jp z,Prog_IconViewer
	jr Prog_ChangeIcon_01

; -----

Prog_DrawCursor:
; Draws the crosshair cursor on the screen at point ( b,c ).  Does not check
; for clipping, but both the SetPixel routine that uses and the
; Prog_ChangeIcon routine that it is called by do.

		dec b
	call SetPixel
		dec b
	call SetPixel
		ld a,b
		add a,3
		ld b,a
	call SetPixel
		inc b
	call SetPixel
		ld a,b
		sub 2
		ld b,a
		dec c
	call SetPixel
		dec c
	call SetPixel
		ld a,c
		add a,3
		ld c,a
	call SetPixel
		inc c
	jp SetPixel

; -----

SetPixel:
; Sets the pixel at screen coordinate ( b , c ).  Checks for clipping.  This
; routine considers the origin to be at the upper-left corner of the screen.

; Throughout this routine's comments, some of the following notation may be
; used:
;	(x-whole) =		The value of the greatest multiple of 8 less than or equal
;					to the value of the abscissa.
;	(x-remainder) =	The value of mod((abscissa),8)
;	(y-offset)/16 =	One sixteenth of the byte offset that needs to be added to
;					the address of Data_Icon to locate the correct byte row (this
;					expression is equal to the ordinate).
;	(y-offset) =	Sixteen times the ordinate, the value of the memory offset
;					created by the ordinate.
;	(offset) =		The total offset from Data_Icon that will be used to locate
;					the byte that the pixel in question is located in.

	ld a,b
	cp 128
	ret nc	; Return if x-coordinate is greater than or equal to 128.

	ld a,c
	cp 64
	ret nc	; Return if y-coordinate is greater than or equal to 64.

	push bc	; Push the word (bc) onto the stack so that it can be restored
			; when this routine is finished.
	ld hl,0		; Zero hl so that h can be used as a counter variable.
SetPixel_01:
	ld a,b				; \ If b is less than 8, jump to
	cp 8				; | SetPixel_02.
	jr c,SetPixel_02	; /
	sub 8		; \ Subtract 8 from the value of b (currently stored in a),
	ld b,a		; | load the new value into b, and increment h, the counter
	inc h		; / register.
	jr SetPixel_01
SetPixel_02:
	ld l,b		; h = (x-whole)
				; l = (x-remainder)
				; c = (y-offset)/16

	ex de,hl	; d = (x-whole)
				; e = (x-remainder)
				; c = (y-offset)/16
	ld hl,graphmem	; Initiate hl, which will contain the memory address of the
					; byte this pixel is located in.  From here, the offset can
					; simply be added to hl to obtain the correct address.
	ld b,0
	ld a,c	; a = (y-offset)/16
	ld c,d	; bc = (x-whole)
	add hl,bc	; hl = graphmem+(x-whole)
	ld c,e	; c = (x-remainder)
	ld e,a	; e = (y-offset)/16
	ld d,0	; Allows de to be equal to e, by zeroing the most signifigant byte.

	ld b,16	; B will be used as the counter register in the following loop.  The
			; loop will, therefore, have 16 iterations.
SetPixel_03:
	add hl,de	; Add (y-offset)/16 to the running total of the offset.  Since,
				; due to the loop, this will be done 16 times, this would be the
				; same as adding (y-offset) to hl.
				; HL = graphmem+(x-whole)+(y-offset) = Address of pixel's byte.
	djnz SetPixel_03	; Decrement b and loop back to SetPixel_03 if b is
						; still greater than zero.

	ld a,c	; a = (x-remainder)
	pop bc	; Pop bc back off the stack, restoring the original values.
	cp 0					; If (x-remainder) is not 0,
		jr nz,SetPixel_04	; jump to SetPixel_04.
		set 7,(hl)	; Set bit 7 (the first bit) of (hl).
		ret		; Done.
SetPixel_04:
	cp 1					; If (x-remainder) is not 1,
		jr nz,SetPixel_05	; jump to SetPixel_05.
		set 6,(hl)	; Set bit 6 (the second bit) of (hl).
		ret		; Done.
SetPixel_05:
	cp 2					; If (x-remainder) is not 2,
		jr nz,SetPixel_06	; jump to SetPixel_06.
		set 5,(hl)	; You get the picture...
		ret	
SetPixel_06:
	cp 3
		jr nz,SetPixel_07
		set 4,(hl)
		ret
SetPixel_07:
	cp 4
		jr nz,SetPixel_08
		set 3,(hl)
		ret
SetPixel_08:
	cp 5
		jr nz,SetPixel_09
		set 2,(hl)
		ret
SetPixel_09:
	cp 6
		jr nz,SetPixel_10
		set 1,(hl)
		ret
SetPixel_10:
		set 0,(hl)
		ret

; -----

Prog_Terminate:
; Closes the program.
	ld a,(Data_IntEnabled)	; \  If the user-int flag wasn't set when
	cp true					;  > the program started, jump to
	jr nz,Prog_Terminate_01	; /  Prog_Terminate_01.
	set 2,(iy+$23)	; Set the user-int flag.
Prog_Terminate_01:
	set indicRun,(iy+indicflags)	; Re-activate the "running" indicator.
	set appAutoScroll,(iy+appflags)	; Turn text scrolling back on.
	set appTextSave,(iy+appflags)	; Turn the text shadow back on.
	call _homeup	; Return cursor to top-left of the screen.
	jp _clrScrn		; Clear the screen memory and the text shadow.

; -----

Prog_Install_Routine:

	ld hl,User_Int_Routine		; Load source address into hl.
	ld de,_user_int_routine		; Load destination address into bc.
	ld bc,IntEnd-IntStart		; Load length of source into bc.
	ldir						; Copy the data.

	ld hl,Data_Icon				; Copy the icon.  Must be done before
	ld de,Icon					; checksum calculation.
	ld bc,48
	ldir

	ld a,(_user_int_routine)			; \
	ld hl,_user_int_routine+($28*1)-1	;  \
	add a,(hl)							;   \
	ld hl,_user_int_routine+($28*2)-1	;    \
	add a,(hl)							;     \
	ld hl,_user_int_routine+($28*3)-1	;      \ Claculate and store checksum
	add a,(hl)							;      / of user interrupt routine.
	ld hl,_user_int_routine+($28*4)-1	;     /
	add a,(hl)							;    /
	ld hl,_user_int_routine+($28*5)-1	;   /
	add a,(hl)							;  /
	ld (_user_int_checksum),a			; /

	ld hl,Data_IntEnabled	; Set Data_IntEnabled, which specifies whether the
	ld (hl),true			; user-int routine should be reactivated when the
							; program terminates, on.
	call _clrScrn
	call _homeup
	ld hl,Data_DoneMsg		; Load the "Done!" message and
	call _puts				; paste it on the screen.
	ld b,60		; Load 60 into b, the counter register for the djnz loop:
Prog_Install_Routine_01:
	halt	; Halt the processor and put it into low-power mode until an
			; interrupt occurs.  Since the next interrupt will almost certainly
			; be caused by the quartz timer, which sets off a maintenance
			; interrupt at 200 Hz (200 times a second), the program will pause
			; 60 times, each time for 1/200 of a second.
	djnz Prog_Install_Routine_01	; Decrement b and loop back to ..._01 if
									; b is greater than zero.
	jp Prog_MainMenu	; Jump back t the main menu routine.

; =====

; Below is the user interrupt routine that this program installs.  None of this
; code is run during program execution.
User_Int_Routine:
	.org _user_int_routine		; set base address to _user_int_routine

IntStart:
		ld hl, $FC00+13			; HL points to display
		ld de, Icon				; DE points to start of sprite
		ld b, 16				; B is counter: There are 16 rows to the sprite.
Loop:
		ld a,(de)				; Get byte from sprite
		ld (hl), a				; Display byte on screen
		inc de
		inc hl
		ld a,(de)				; Get next byte (will be on same line).
		ld (hl),a				; Display byte on screen.
		inc de
		inc hl
		ld a,(de)
		ld (hl),a
		inc de
		push bc
		ld bc,14
		add hl,bc
		pop bc

		djnz Loop				; Loop back if there is another row to be printed.
		ret

		.dw $0000	; I insert a word here so that this program
					; does not use the same memory for the sprite as
					; another of my programs does, preventing the two
					; from being incompatible... hard to explain, but
					; it does have a purpose.

					; (Feel free to remove those two bytes, then, if your calc's
					; _that_ short on memory... :P)
Icon:
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
		.db $00, $00, $00
IntEnd:


; =====

.end