User:Zzo38/Famicom Z-machine: Difference between revisions

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This program is being written by [[User:Zzo38]], and is using the Famicom keyboard. It is not yet complete (and likely contains errors).
This program is being written by [[User:Zzo38]], and is using the Famicom keyboard. It is not yet complete (and likely contains errors).
__TOC__


== Main file ==
== Main file ==
Line 3,215: Line 3,217:


== Explanation ==
== Explanation ==
The explanation of the mapper is [[User:Zzo38/Mapper_I]].


The pattern table is arranged in this way (although $7F is the cursor picture, not shown here):
The pattern table is arranged in this way (although $7F is the cursor picture, not shown here):
Line 3,252: Line 3,256:


Instruction decoding tables, as well as the Z-character decoding tables, both use the RTS trick, although in the case of Z-character decoding, the table contains only the low byte of the address since the code is small enough in this case.
Instruction decoding tables, as well as the Z-character decoding tables, both use the RTS trick, although in the case of Z-character decoding, the table contains only the low byte of the address since the code is small enough in this case.
Also it is using several stable unofficial opcodes.

Latest revision as of 09:31, 20 April 2016

This file contains a copy of the working in progress for the Famicom Z-machine interpreter program.

You are free to review it, question/comment, and even to modify it if you have improvements to make. It is placed here mainly in order to improve reviewing of the software, but you can use it for other purposes too.

The assembler in use is Unofficial MagicKit (a modified version of NESASM).

This program is being written by User:Zzo38, and is using the Famicom keyboard. It is not yet complete (and likely contains errors).

Main file

; Famizork II
; Public domain

debug	= 1  ; change this to 1 to enable breakpoints 0 to disable
	     ; set a breakpoint on opcode $1A in the debugger

	inesmap 380 ; Famizork II mapper
	ineschr 1 ; 8K CHR ROM
	inesmir 3 ; horizontal arrangement with battery

; Zero-page variables:
;   $02 = data stack pointer
;   $03 = call stack pointer
;   $04 = temporary
;   $05 = temporary
;   $06 = temporary
;   $07 = temporary
;   $09 = current temporary shift state
;   $0A = current permanent shift state
;   $0B = saved permanent shift state
;   $0D = number of locals
;   $0E = bit16 of program counter
;   $10 = bit7-bit0 of program counter
;   $11 = low byte of first operand
;   $12 = low byte of second operand
;   $13 = low byte of third operand
;   $14 = low byte of fourth operand
;   $15 = temporary
;   $16 = low byte of text address if inside fword
;   $17 = low byte of packed word
;   $18 = temporary
;   $19 = low byte of packed word if inside fword
;   $20 = bit15-bit8 of program counter
;   $21 = high byte of first operand
;   $22 = high byte of second operand
;   $23 = high byte of third operand
;   $24 = high byte of fourth operand
;   $25 = temporary
;   $26 = high byte of text address if inside fword
;   $27 = high byte of packed word
;   $28 = temporary
;   $29 = high byte of packed word if inside fword
;   $30 = output buffer pointer
;   $31 = low byte of nametable address of cursor
;   $32 = high byte of nametable address of cursor
;   $33 = Y scroll amount
;   $34 = lines to output before <MORE>
;   $35 = saved high byte of return address for text unpacking
;   $36 = bit16 of current text address
;   $37 = bit16 of current text address if inside fword
;   $38-$39 = return address for text unpacking
;   $3A = current background color
;   $3B = current foreground color
;   $3C = remember if battery RAM is present (255=yes 0=no)
;   $3D = ARCFOUR "i" register 
;   $3E = ARCFOUR "j" register
;   $40-$4F = low byte of locals
;   $50-$5F = high byte of locals
;   $E2-$FF = output buffer

	code

datasp	= $02
callsp	= $03
locall	= $40
localh	= $50

dstackl	= $200
dstackh	= $300

cstackl	= $400
cstackm	= $480
cstackh	= $500 ; bit4-bit1=number of locals, bit0=bit16 of PC
cstackx	= $580 ; data stack pointer

arcfour	= $600 ; use for random number generator

	bank intbank+0,"Interpreter"
	bank intbank+1,"Interpreter"
	bank intbank+2,"Interpreter"
	bank intbank+3,"Interpreter"

	bank intbank
	org $8000

	macro breakpoint
	if debug
	db $1A ; unofficial NOP
	endif
	endm

	macro breakpoint2
	if debug
	db $3A ; unofficial NOP
	endif
	endm

	macro make_digit_table
	macset 4,4,0
	macgoto make_digit_table_0
	endm

	macro make_digit_table_0
	db ((\4*\2)/\1)%10
	macset 4,4,\4+1
	macset 5,4,\4=\3
	macgoto make_digit_table_\5
	endm

	macro make_digit_table_1
	; Empty macro
	endm

globodd	= global&1

	macro make_global_table
	macset 2,4,16
	macgoto make_global_table_0
	endm

	macro make_global_table_0
	db \1(global+\2+\2-32)
	macset 2,4,\2+1
	macset 3,4,\2=256
	macgoto make_global_table_\3
	endm

	macro make_global_table_1
	; Empty macro
	endm

	macro make_object_table
	macset 2,4,0
	macgoto make_object_table_0
	endm

	macro make_object_table_0
	db \1(object+(\2*9)+62-9)
	macset 2,4,\2+1
	macset 3,4,\2=256
	macgoto make_object_table_\3
	endm

	macro make_object_table_1
	; Empty macro
	endm

instadl	ds 256
instadh	ds 256

globadl	ds 16
	make_global_table low
globadh	ds 16
	make_global_table high

objadl	make_object_table low
objadh	make_object_table high

multabl	ds 256 ; x*x/4
multabh	ds 512 ; x*x/1024

digit0l	make_digit_table 1,1,256
digit1l	make_digit_table 10,1,256
digit2l	make_digit_table 100,1,256
digit0h	make_digit_table 1,256,128
digit1h	make_digit_table 10,256,128
digit2h	make_digit_table 100,256,128
digit3h	make_digit_table 1000,256,128

bit1tab	db   0,  1,  3,  3,  7,  7,  7,  7, 15, 15, 15, 15, 15, 15, 15, 15
	db  31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31
	db  63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63
	db  63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63
	db 127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127
	db 127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127
	db 127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127
	db 127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255
	db 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255

zchad	ds 256

ptsizt	db 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
	db 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
	db 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3
	db 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4
	db 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5
	db 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6
	db 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
	db 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8

flagad	if smalend
	db 1,1,1,1,1,1,1,1
	db 0,0,0,0,0,0,0,0
	db 3,3,3,3,3,3,3,3
	db 2,2,2,2,2,2,2,2
	else
	db 0,0,0,0,0,0,0,0
	db 1,1,1,1,1,1,1,1
	db 2,2,2,2,2,2,2,2
	db 3,3,3,3,3,3,3,3
	endif

fwordsl	= *-32
	ds 96
fwordsh	= *-32
	ds 96

flagbit	db 128,64,32,16,8,4,2,1
	db 128,64,32,16,8,4,2,1
	db 128,64,32,16,8,4,2,1
	db 128,64,32,16,8,4,2,1

flagbic	db 127,191,223,239,247,251,253,254
	db 127,191,223,239,247,251,253,254
	db 127,191,223,239,247,251,253,254
	db 127,191,223,239,247,251,253,254

digit4h	make_digit_table 10000,256,128

	; Z-character-decoding assigning macro
	macro def_zchars
	if \#=1
	macset 2,4,\1
	else
	macset 2,4,\2
	endif
	macset 1,4,\1
	macset 3,4,*
	macset 4,4,?B
	bank bank(zchad)
	macgoto def_zchars_0
	endm

	macro def_zchars_0
	macset 5,4,\1=\2
	org zchad+\1
	db low(\3-1)
	if \3<$FE01
	fail "Z-character routine out of range"
	endif
	if \3>$FF00
	fail "Z-character routine out of range"
	endif
	macset 1,4,\1+1
	macgoto def_zchars_\5
	endm

	macro def_zchars_1
	bank \4
	org \3
	endm

	; Instruction assigning macro
	macro def_inst
	macset 2,4,*
	macset 3,4,?B
	bank bank(instadl)
	org instadl+(\1)
	db low(\2-1)
	org instadh+(\1)
	db high(\2-1)
	bank \3
	org \2
	endm

	macro def_inst_2op
	def_inst (\1)+$00
	def_inst (\1)+$20
	def_inst (\1)+$40
	def_inst (\1)+$60
	def_inst (\1)+$C0
	endm

	macro def_inst_2op_eq
	def_inst (\1)+$00
	def_inst (\1)+$20
	def_inst (\1)+$40
	def_inst (\1)+$60
	endm

	macro def_inst_1op
	def_inst (\1)+$00
	def_inst (\1)+$10
	def_inst (\1)+$20
	endm

	macro def_inst_0op
	def_inst (\1)+$00
	endm

	macro def_inst_ext
	def_inst (\1)+$00
	endm

	; Fetch next byte of program
	; Doesn't affect carry flag and overflow flag
	macro fetch_pc
	inc $1010
	bne n\@
	inc $1020
	if large
	bne n\@
	inc <$0E
n\@	ld\1 <$0E
	\2 $5803,\1
	else
n\@	\2 $5803
	endif
	endm
	; (Bytes of above: 17)
	; (Cycles of above: 16 or 25 or 27)

	; Initialization code
reset	ldx #0
	stx $2000
	stx $2001
	; Wait for frame
	bit $2002
vwait1	bit $2002
	bpl vwait1
	txa
	stx <$0E ; bit16 of program counter
	stx <$0D ; number of locals
	stx <$33 ; Y scroll amount
	stx <$3C ; battery flag
	dex
	stx <$03 ; call stack pointer
	ldy #27
	sty <$34 ; lines before <MORE>
	ldy #$0F
	sty <$3A ; background
	ldy #$20
	sty <$3B ; foreground
	ldy #low(start-1)
	sty <$10
	ldy #$E2
	sty <$30 ; output buffer pointer
	ldy #$61
	sty <$31 ; low byte of cursor nametable address
	ldy #$27
	sty <$32 ; high byte of cursor nametable address
	; Wait for frame
	bit $2002
vwait2	bit $2002
	bpl vwait2
	; Clear the screen
	tax
	lda #32
	sta $2006
	ldx #9
	stx $2006
reset1	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	inx
	bne reset1
	; Initialize palette
	lda #$FF
	sta $2006
	stx $2006
	lda <$3A
	sta $2007
	sta $2007
	ldy <$3B
	sty $2007
	sty $2007
	sta $2007
	sta $2007
	sty $2007
	sty $2007
	sta $2007
	sta $2007
	sty $2007
	sty $2007
	sta $2007
	sta $2007
	sty $2007
	sty $2007
	; Check if F8 is pushed (erases save data)
	ldx #5
	stx $4016
	dex
	stx $4016
	lda $4017
	and #2
	beq reset2
	; Check battery
	ldx #0
	stx $1011
	stx $1021
	lda $5800
	cmp #69
	bne reset2
	inc $1011
	lda $5800
	cmp #105
	beq reset3
	; No save file exists; try to create one
reset2	stx $1011
	lda #69
	sta $5800
	inc $1011
	lda #105
	sta $5800
	inc $1011
	stx $5800
	lda #$FF
	sta $1022
	; Initialize ARCFOUR table
reset2a	txa
	sta arcfour,x
	sta $1012
	sta $5800
	inx
	bne reset2a
	; Copy header from ROM into RAM
	stx $1021
reset2b	stx $1011
	lda $5805
	sta $5803
	inx
	bne reset2b
	; Copy ROM starting from PURBOT into RAM
	lda #high(purbot)
	sta $1021
	lda #low(purbot)
	sta $1011
reset2c	lda $5805
	sta $5803
	inc $1011
	bne reset2c
	inc $1021
	if large=0
	if maxaddr<$FF00
	lda <$21
	cmp #high(maxaddr)+1
	endif
	endif
	bne reset2c
	; Check if save file still exists
	stx $1011
	stx $1021
	lda $5800
	cmp #69
	bne zrest
	inc $1011
	lda $5800
	cmp #105
	beq reset3
	jmp zrest
	; Battery is OK
reset3	lda #255
	sta <$3C
	; Load and permute saved ARCFOUR table
	sta $1021
	ldy #0
reset3a	sty $1011
	lax $5800
	sta arcfour,y
	inx
	stx $5800
	iny
	bne reset3a
	; fall through

	; *** RESTART
	def_inst_0op 183
zrest	ldx #0
	stx <$0E ; bit16 of program counter
	stx <$0D ; number of locals
	stx $1021
	dex
	stx <$03 ; call stack pointer
	; Load data from 64 to PURBOT from ROM into RAM
	lda #64
	sta $1011
zrest1	lda $5805
	sta $5803
	inc $1011
	bne zrest1
	inc $1021
	if purbot<$FF00
	lda <$21
	cmp #high(purbot)+1
	endif
	bne zrest1
	; Initialize program counter
	lda #low(start-1)
	sta <$10
	lda #high(start-1)
	sta $1020
	jmp zcrlf

	; *** USL
	def_inst_0op 188
	; fall through

	; *** SPLIT
	def_inst_ext 234
	; fall through

	; *** SCREEN
	def_inst_ext 235
	; fall through

	; *** NOOP
	def_inst_0op 180
	; fall through

	; Decode the next instruction
	; For EXT instructions, number of operands is in the X register
nxtinst	fetch_pc y,ldx
	lda instadh,x
	pha
	lda instadl,x
	pha
	txa
	bmi not2op

	; It is 2OP
	ldx #0
	asl a
	sta <4
	arr #$C0
	fetch_pc y,lda
	bcc is2op1
	jsr varop0
	fetch_pc y,lda
	bvc is2op2
	jmp is2op3
is2op1	stx <$21
	sta <$11
	bit <4
	fetch_pc y,lda
	bvc is2op3
is2op2	inx
	jmp varop0
is2op3	stx <$22
	sta <$12
	rts

	; It isn't 2OP
not2op	cmp #192
	bcc notext

	; It is EXT
	fetch_pc y,lda
	ldx #0
isext0	sec
	rol a
	bcs isext1
	bmi isext3

	; Long immediate
	sta <4
	fetch_pc y,lda
	if smalend
	sta <$11,x
	else
	sta <$21,x
	endif
	fetch_pc y,lda
	if smalend
	sta <$21,x
	else
	sta <$11,x
	endif
	inx
	lda <4
	sec
	rol a
	jmp isext0

	; Variable or no more operands
isext1	bpl isext2

	; No more operands
	rts

	; Variable
isext2	sta <4
	jsr varop
	inx
	lda <4
	sec
	rol a
	jmp isext0

	; Short immediate
isext3	sta <4
	lda #0
	sta <$21,x
	fetch_pc y,lda
	sta <$11,x
	inx
	lda <4
	sec
	rol a
	jmp isext0

	; It isn't EXT; it is 1OP or 0OP
notext	asl a
	asl a
	asl a
	bcs notext1
	bpl notext2

	; 1OP - short immediate
	fetch_pc y,lda
	ldx #0
	stx <$21
	sta <$11
	rts

notext1	bmi notext3

	; 1OP - variable
	ldx #0
	jmp varop

	; 1OP - long immediate
notext2	fetch_pc y,lda
	if smalend
	sta <$11,x
	else
	sta <$21,x
	endif
	fetch_pc y,lda
	if smalend
	sta <$21,x
	else
	sta <$11,x
	endif
	; fall through

	; 0OP
notext3	rts

zcall0	jmp val8

	; *** CALL
	def_inst_ext 224
	stx <4
	lax <$11
	ora <$21
	beq zcall0 ; calling function zero
	; Save to call stack
	inc <callsp
	ldy <callsp
	lda <$10
	stx <$10
	sta cstackl,y
	lda <$20
	sta cstackm,y
	lsr <$0E
	lax <$0D
	rol a
	sta cstackh,y
	lda <datasp
	sta cstackx,y
	; Save locals
	txa
	beq zcall2
	clc
	adc <datasp
	tay
zcall1	lda <locall,x
	sta dstackl,y
	lda <localh,x
	sta dstackh,y
	dey
	dex
	bne zcall1
	lda <$0D
	adc <datasp
	sta <datasp
	; Read function header (number of locals)
zcall2	asl $1010
	lda <$21
	rol a
	sta $1020
	rol <$0E
	ldy <$0E
	lda $5803,y
	sta <$0D
	; Load initial values of locals
	beq zcall4
	; Load arguments
	ldx <4
	dex
	beq zcall3
	lda <$12
	sta <$41
	lda <$22
	sta <$51
	cpx #1
	beq zcall2a
	lda <$13
	sta <$42
	lda <$23
	sta <$52
	cpx #2
	beq zcall2a
	lda <$14
	sta <$43
	lda <$24
	sta <$53
zcall2a	txa
	asl a ; now clears carry flag
	adc <$10
	sta <$10
	lda #0
	adc <$20
	sta $1020
	if large
	bcc zcall3
	inc <$0E
	endif
	; Load default values
zcall3	fetch_pc y,lda
	if smalend
	sta <locall+1,x
	else
	sta <localh+1,x
	endif
	fetch_pc y,lda
	if smalend
	sta <localh+1,x
	else
	sta <locall+1,x
	endif
	inx
	cpx <$0D
	bne zcall3
zcall4	jmp nxtinst

	; *** RFALSE
	def_inst_0op 177
	lda #0
	; fall through

	; Return a 8-bit value (from A)
ret8	pha
	ldy <callsp
	dec <callsp
	lda cstackx,y
	sta <datasp
	lda cstackl,y
	sta <$10
	lda cstackm,y
	sta $1020
	lda cstackh,y
	lsr a
	sta <$0D
	tax
	rol a
	anc #1
	sta <$0E
	; Restore locals
	txa
	beq ret8b
	adc <datasp
	tay
ret8a	lda dstackl,y
	sta <locall,x
	lda dstackh,y
	sta <localh,x
	dey
	dex
	bne ret8a
ret8b	pla
	; fall through

	; Value of instruction is 8-bits (from A)
val8	fetch_pc y,ldx
	bne val8a
	; Push to stack
	inc <datasp
	ldy <datasp
	sta dstackl,y
	txa
	sta dstackh,y
	jmp nxtinst
val8a	cpx #16
	bcs val8b
	; Local variable
	sta <locall,x
	lda #0
	sta <localh,x
	jmp nxtinst
	; Global variable
val8b	ldy globadl,x
	sty $1014
	ldy globadh,x
	sty $1024
	if smalend
	sta $5801
	else
	ldy #0
	sty $5801
	endif
	inc $1014
	if globodd
	bne val8c
	inc $1024
	endif
val8c	if smalend
	lda #0
	endif
	sta $5801
	lda $1020
	jmp nxtinst

	; Read the variable using as an instruction operand
	; X is operand number (0-3)
varop	fetch_pc y,lda
varop0	bne varop1
	; Pop from stack
	ldy <datasp
	dec <datasp
	lda dstackl,y
	sta <$11,x
	lda dstackh,y
	sta <$21,x
	rts
varop1	cmp #16
	bcs varop2
	; Local variable
	tay
	lda locall,y
	sta <$11,x
	lda localh,y
	sta <$21,x
	rts
	; Global variable
varop2	tay
	lda globadl,y
	sta $1015
	lda globadh,y
	sta $1025
	lda $5801
	if smalend
	sta <$11,x
	else
	sta <$21,x
	endif
	inc $1015
	if globodd
	bne varop3
	inc $1025
	endif
varop3	lda $5801
	if smalend
	sta <$21,x
	else
	sta <$11,x
	endif
	lda $1020
	rts

	; *** RSTACK
	def_inst_0op 184
	ldx <datasp
	lda dstackl,x
	sta <$14
	lda dstackh,x
	jmp ret16

	; *** RETURN
	def_inst_1op 139
	lda <$11
	sta <$14
	lda <$21
ret16	sta <$24
	ldy <callsp
	dec <callsp
	lda cstackx,y
	sta <datasp
	lda cstackl,y
	sta <$10
	lda cstackm,y
	sta $1020
	lda cstackh,y
	lsr a
	sta <$0D
	tax
	rol a
	anc #1
	sta <$0E
	; Restore locals
	txa
	beq ret16b
	adc <datasp
	tay
ret16a	lda dstackl,y
	sta <locall,x
	lda dstackh,y
	sta <localh,x
	dey
	dex
	bne ret16a
ret16b	; fall through

	; Value of instruction is 16-bits (from $x4)
val16	lda <$14
	fetch_pc y,ldx
	bne val16a
	; Push to stack
	inc <datasp
	ldy <datasp
	sta dstackl,y
	lda <$24
	sta dstackh,y
	jmp nxtinst
val16a	cpx #16
	bcs val16b
	; Local variable
	sta <locall,x
	lda <$24
	sta <localh,x
	jmp nxtinst
	; Global variable
val16b	ldy globadl,x
	sty $1015
	ldy globadh,x
	sty $1025
	if smalend
	sta $5801
	else
	ldy <$24
	sty $5801
	endif
	inc $1015
	if globodd
	bne val16c
	inc $1025
	endif
val16c	if smalend
	lda <$24
	endif
	sta $5801
	lda $1020
	jmp nxtinst

	; *** RTRUE
	def_inst_0op 176
	lda #1
	jmp ret8

	; *** EQUAL? (EXT)
	def_inst_ext 193
	lda <$11
	ldy <$21
	cmp <$12
	bne zequal1
	cpy <$22
	beq tpredic
zequal1	cpx #2
	beq fpredic
	cmp <$13
	bne zequal2
	cpy <$23
	beq tpredic
zequal2	cpx #3
	beq fpredic
	cmp <$14
	bne fpredic
	cmp <$24
	beq tpredic
	jmp fpredic

	; *** GRTR?
	def_inst_2op 3
	lda <$12
	cmp <$11
	lda <$22
	sbc <$21
	bvc zgrtr1
	and #128
	jmp predic1
zgrtr1	bmi tpredic
	jmp fpredic

	; *** LESS?
	def_inst_2op 2
	lda <$11
	cmp <$12
	lda <$21
	sbc <$22
	bvc zgrtr1
	and #128
	jmp predic1

	; *** EQUAL? (2OP)
	def_inst_2op_eq 1
	lda <$11
	eor <$21
	bne fpredic
	lda <$12
	eor <$22
	beq predic1
	jmp fpredic

	; *** ZERO?
	def_inst_1op 128
	lda <$11
	ora <$21
	beq tpredic
	; falls through

	; Predicate handling
fpredic	lda #128
	jmp predic1
tpredic	lda #0
predic1	fetch_pc x,eor
	tax
	arr #$C0
	bcs predic8

	; If it should branch
	txa
	bvs predic3

	; Long offset
	eor #$20
	anc #$3F
	adc #$E0
	if large
	bpl predic2
	dec <$0E
	endif
predic2	clc
	adc <$20
	sta $1020
	if large
	bcc predick
	inc <$0E
	endif
predick	fetch_pc y,lax
	jmp predic4

	; Short offset
predic3	and #$3F
	cmp #2
	bcc predicq
predic4	sbc #2
	bcs predic5
	if large
	ldy <$20
	dey
	sty $1020
	cpy #255
	bne predic5
	lsr <$0E
	else
	dec $1020
	endif
predic5	sec
	adc <$10
	sta <$10
	bcc predic9
	inc $1020
	if large
	bne predic9
	inc <$0E
	endif
	jmp nxtinst

	; If should not branch
predic8	bvc predic9
	inc <$10
	bne predic9
	inc $1020
	if large
	bne predic9
	inc <$0E
	endif
predic9	jmp nxtinst

predicq	jmp ret8

	; *** IGRTR?
	def_inst_2op 5
	ldx <$11
	jsr xvalue
	inc <$14
	bne zigrtr2
	inc <$24
zigrtr1	jsr xstore
	lda <$14
	cmp <$11
	lda <$24
	sbc <$21
	bvc zigrtr2
	and #128
	jmp predic1
zigrtr2	bmi zigrtr3
	jmp fpredic
zigrtr3	jmp tpredic

	; *** DLESS?
	def_inst_2op 4
	ldx <$11
	jsr xvalue
	ldy <$14
	dey
	sty <$14
	cpy #255
	bne zdless1
	dec <$24
zdless1	jsr xstore
	lda <$11
	cmp <$14
	lda <$21
	sbc <$24
	bvc zigrtr2
	and #128
	jmp predic1

	; *** PTSIZE
	def_inst_1op 132
	lda $1021
	ora #255
	dcp $1011
	bne zptsz1
	dec $1021
zptsz1	ldx $5801
	lda ptsizt,x
	jmp val8

	; *** PUT
	def_inst_ext 225
	lda <$12
	asl a
	rol <$22
	clc
	adc <$11
	sta $1011
	lda <$22
	adc <$21
	sta $1021
	if smalend
	lda <$13
	else
	lda <$23
	endif
	sta $5801
	inc $1011
	bne zput1
	inc $1021
zput1	ds 0
	if smalend
	lda <$23
	else
	lda <$13
	endif
	sta $5801
	bit $1020
	jmp nxtinst

	; *** PUTB
	def_inst_ext 226
	lda <$12
	clc
	adc <$11
	sta $1011
	lda <$22
	adc <$21
	sta $1021
	lda <$13
	sta $5801
	bit $1020
	jmp nxtinst

	; *** GET
	def_inst_2op 15
	lda <$12
	asl a
	rol <$22
	clc
	adc <$11
	sta $1011
	lda <$22
	adc <$21
	sta $1021
	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	inc $1011
	bne zget1
	inc $1021
zget1	ds 0
	lda $5801
	if smalend
	sta <$24
	else
	sta <$14
	endif
	bit $1020
	jmp val16

	; *** GETB
	def_inst_2op 16
	lda <$12
	clc
	adc <$11
	sta $1011
	lda <$22
	adc <$21
	sta $1021
	lda $5801
	bit $1020
	jmp val8

	; *** ADD
	def_inst_2op 20
	clc
	lda <$11
	adc <$12
	sta <$14
	lda <$21
	adc <$22
	sta <$24
	jmp val16

	; *** SUB
	def_inst_2op 21
	sec
	lda <$11
	sbc <$12
	sta <$14
	lda <$21
	sbc <$22
	sta <$24
	jmp val16

	; *** BAND
	def_inst_2op 9
	lda <$11
	and <$12
	sta <$14
	lda <$21
	and <$22
	sta <$24
	jmp val16

	; *** BOR
	def_inst_2op 8
	lda <$11
	ora <$12
	sta <$14
	lda <$21
	ora <$22
	sta <$24
	jmp val16

	; *** BCOM
	def_inst_1op 143
	lda <$11
	eor #$FF
	sta <$14
	lda <$21
	eor #$FF
	sta <$24
	jmp val16

	; *** BTST
	def_inst_2op 7
	lda <$11
	and <$12
	eor <$12
	sta <4
	lda <$21
	and <$22
	eor <$22
	ora <4
	bne zbtst1
	jmp predic1
zbtst1	jmp fpredic

	; *** MUL
	def_inst_2op 22
	lax <$11
	clc
	adc <$12
	bcc zmul1
	eor #255
	adc #0
zmul1	tay
	txa
	sec
	sbc <$12
	bcs zmul2
	eor #255
	adc #1
	sec
zmul2	tax
	lda multabl,y
	sbc multabl,x
	sta <$14
	php
	lda <$11
	clc
	adc <$12
	tay
	bcc zmul3
	lda multabh+256,y
	jmp zmul4
zmul3	lda multabh,y
zmul4	plp
	sbc multabh,x
	sta <$24
	; low*high
	lax <$11
	clc
	adc <$22
	bcc zmul5
	eor #255
	adc #0
zmul5	tay
	txa
	sec
	sbc <$22
	bcs zmul6
	eor #255
	adc #1
	sec
zmul6	tax
	lda multabl,y
	sbc multabl,x
	clc
	adc <$24
	sta <$24
	; high*low
	lax <$21
	clc
	adc <$12
	bcc zmul7
	eor #255
	adc #0
zmul7	tay
	txa
	sec
	sbc <$12
	bcs zmul8
	eor #255
	adc #1
	sec
zmul8	tax
	lda multabl,y
	sbc multabl,x
	clc
	adc <$24
	sta <$24
	jmp val16

	; *** PUSH
	def_inst_ext 232
	inc <datasp
	ldx <datasp
	lda <$11
	sta dstackl,x
	lda <$21
	sta dstackh,x
	jmp nxtinst

	; *** POP
	def_inst_ext 233
	ldx <datasp
	dec <datasp
	lda dstackl,x
	sta <$12
	lda dstackh,x
	sta <$22
	ldx <$11
	jsr xstore
	jmp nxtinst

	; *** FSTACK
	def_inst_0op 185
	dec <datasp
	jmp nxtinst

	; *** SET
	def_inst_2op 13
	lda <$12
	sta <$14
	lda <$22
	sta <$24
	ldx <$11
	jsr xstore
	jmp nxtinst

	; *** VALUE
	def_inst_1op 142
	ldx <$11
	jsr xvalue
	jmp val16

	; *** INC
	def_inst_1op 133
	ldx <$11
	jsr xvalue
	inc <$14
	bne zinc1
	inc <$24
zinc1	jsr xstore
	jmp nxtinst

	; *** DEC
	def_inst_1op 134
	ldx <$11
	jsr xvalue
	ldy <$14
	dey
	sty <$14
	cpy #255
	bne zinc1
	dec <$24
	jsr xstore
	jmp nxtinst

	; Store value from <$x4 into variable labeled X
xstore	lda <$14
	cpx #0
	bne xstore1
	; Top of stack
	ldy <datasp
	sta dstackl,y
	lda <$24
	sta dstackh,y
	rts
xstore1	cpx #16
	bcs xstore2
	; Local variable
	sta <locall,x
	lda <$24
	sta <localh,x
	rts
	; Global variable
xstore2	ldy globadl,x
	sty $1014
	ldy globadh,x
	sty $1024
	if smalend
	sta $5801
	else
	ldy <$24
	sty $5801
	endif
	inc $1014
	if globodd
	bne xstore3
	inc $1024
	endif
xstore3	if smalend
	lda <$24
	endif
	sta $5801
	lda $1020
	rts

	; Read from variable labeled X into <$x4
xvalue	txa
	bne xvalue1
	; Top of stack
	ldy <datasp
	lda dstackl,y
	sta <$14
	lda dstackh,y
	sta <$24
	rts
xvalue1	cpx #16
	bcs xvalue2
	; Local variable
	lda <locall,x
	sta <$14
	lda <localh,x
	sta <$24
	rts
	; Global vaiable
xvalue2	ldy globadl,x
	sty $1015
	ldy globadh,x
	sty $1025
	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	inc $1015
	if globodd
	bne xvalue3
	inc $1025
	endif
xvalue3	lda $5801
	if smalend
	sta <$24
	else
	sta <$14
	endif
	bit $1020
	rts

	; *** IN?
	def_inst_2op 6
	ldx <$11
	clc
	lda objadl,x
	adc #4
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	bit $1020
	eor <$21
	bne zin1
	jmp predic1
zin1	jmp fpredic

	; *** FSET?
	def_inst_2op 10
	ldx <$11
	ldy <$12
	clc
	lda objadl,x
	adc flagad,y
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	and flagbit,y
	bne zfsetp1
	bit $1020
	jmp predic1
zfsetp1	jmp fpredic

	; *** FSET
	def_inst_2op 11
	ldx <$11
	ldy <$12
	clc
	lda objadl,x
	adc flagad,y
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	ora flagbit,y
	sta $5801
	bit $1020
	jmp nxtinst

	; *** FCLEAR
	def_inst_2op 12
	ldx <$11
	ldy <$12
	clc
	lda objadl,x
	adc flagad,y
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	and flagbic,y
	sta $5801
	bit $1020
	jmp nxtinst

	; *** LOC
	def_inst_1op 131
	ldx <$11
	clc
	lda objadl,x
	adc #4
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	bit $1020
	jmp val8

	; *** FIRST?
	def_inst_1op 130
	ldx <$11
	clc
	lda objadl,x
	adc #6
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	bit $1020
	jmp valp

	; *** NEXT?
	def_inst_1op 129
	ldx <$11
	clc
	lda objadl,x
	adc #5
	sta $5010
	lda objadh,x
	adc #0
	sta $5020
	lda $5801
	bit $1020
	; fall through

	; Value of instruction is 8-bits (from A)
	; Predicate is then if value is nonzero
valp	fetch_pc y,ldx
	bne valpa
	; Push to stack
	inc <datasp
	ldy <datasp
	sta dstackl,y
	sta <4
	txa
	sta dstackh,y
	lda <4
	jmp valpd1
valpa	cpx #16
	bcs valpb
	; Local variable
	sta <locall,x
	ldy #0
	sty <localh,x
	jmp valpd
	; Global variable
valpb	ldy globadl,x
	sty $1014
	ldy globadh,x
	sty $1024
	if smalend
	sta $5801
	else
	ldy #0
	sty $5801
	endif
	inc $1014
	if globodd
	bne valpc
	inc $1024
	endif
valpc	if smalend
	ldy #0
	sty $5801
	else
	sta $5801
	endif
	bit $1020
valpd	tax
valpd1	beq valpe
	jmp fpredic
valpe	jmp tpredic

	; Macro to do one step of ARCFOUR
	; Result is stored in accumulator
	macro do_arcfour
	inc <$3D
	ldx <$3D
	lda arcfour,x
	pha
	clc
	adc <$3E
	sta <$3E
	tay
	sta arcfour,y
	pla
	sta arcfour,x
	clc
	adc arcfour,y
	tax
	lda arcfour,x
	endm

	; *** RANDOM
	def_inst_ext 231
	ldx <$21
	beq zrand1
	lda bit1tab,x
	sta <$23
	lda #$FF
	jmp zrand2
zrand1	ldx <$11
	lda bit1tab,x
zrand2	sta <$13
zrand3	do_arcfour
	and <$23
	sta <$24
	cmp <$21
	beq zrand4 ; exactly equal
	bcs zrand1 ; try again; out of range
	jmp zrand5 ; low byte doesn't need to check
zrand4	do_arcfour
	and <$13
	cmp <$11
	bcs zrand1 ; try again; out of range
	adc #1
	sta <$14
	jmp zrand6
zrand5	do_arcfour
	sec
	adc #0
	sta <$14
zrand6	lda #0
	adc <$24
	sta <$24
	jmp val16

	; *** JUMP
	def_inst_1op 140
	lda <$11
	sec
	sbc #2
	tax
	lda <$21
	sbc #0
	tay
	bpl zjump1
	dec <$0E
zjump1	txa
	clc
	adc <$10
	sta <$10
	tya
	adc <$20
	sta $1020
	bcc zjump2
	inc <$0E
zjump2	jmp nxtinst

	; Macro to find a property, given object and property number
	; Object in <$11, property in <$12, branch to \1 if found
	; If \1 is with # at front then assume always will be found
	; X contains property size only in high 3-bits if found
	; X contains property number if not found
	; Output is $1014 and $1024 with address of property id
	macro propfind
	; Find the property table
	ldx <$11
	clc
	lda objadl,x
	adc #7
	sta $1015
	lda objadh,x
	adc #0
	sta $1025
	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	inc $1015
	bne n\@a
	inc $1025
n\@a	lda $5801
	if smalend
	sta $1014
	bit $1024
	else
	sta $1024
	bit $1014
	endif
	; Skip the short description
	lda $5801
	sec
	rol a
	bcc n\@d
	inc $1024
	clc
n\@d	adc <$14
	sta $1014
	bcc n\@b
	inc $1024
	; Find this property
n\@b	lda $5081
	if '\<1'!='#'
	beq n\@c
	endif
	eor <$12
	tax
	and #$1F
	if '\<1'='#'
	beq n\@c
	else
	beq \1
	endif
	lda ptsizt,x
	sec
	adc <$14
	sta $1014
	bcc n\@b
	inc $1024
	jmp n\@b
n\@c	ds 0
	endm

	; *** GETPT
	def_inst_2op 18
	propfind zgetpt1
	lda $1020
	and #0
	jmp val8
zgetpt1	lda $1020
	inc <$14
	bne zgetpt2
	inc <$24
zgetpt2	jmp val16	

	; *** GETP
	def_inst_2op 17
	propfind zgetp2
	; Use default value
	asl <$11
	rol <$21 ;clears carry
	lda #low(object-2)
	adc <$11
	sta $1015
	lda #high(object-2)
	adc <$21
	sta $1025
	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	inc $1015
	if object&1
	bne zgetp1
	inc $1025
	endif
zgetp1	lda $5801
	if smalend
	sta <$24
	else
	sta <$14
	endif
	bit $1020
	jmp val16
	; Use actual value
zgetp2	inc $1014
	bne zgetp3
	inc $1024
zgetp3	cpx #$20
	bne zgetp5
	; Long property
	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	inc $1014
	bne zgetp4
	inc $1024
zgetp4	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	jmp val16
	; Short property
zgetp5	lda $5801
	bit $1020
	jmp val8

	; *** PUTP
	def_inst_ext 227
	propfind #
	inc $1014
	bne zputp2
	inc $1024
zputp2	cpx #$20
	bne zputp4
	; Long property
	if smalend
	lda <$13
	else
	lda <$23
	endif
	sta $5801
	inc $1014
	bne zputp3
	inc $1024
zputp3	if smalend
	lda <$23
	else
	lda <$13
	endif
	sta $5801
	lda $1020
	jmp nxtinst
	; Short property
zputp4	lda <$13
	sta $5801
	lda $1020
	jmp nxtinst

	; *** NEXTP
	def_inst_2op 19
	ldx <$11
	bne znextp4
	; Find first property
	clc
	lda objadl,x
	adc #7
	sta $1015
	lda objadh,x
	adc #0
	sta $1025
	lda $5801
	if smalend
	sta <$14
	else
	sta <$24
	endif
	inc $1015
	bne znextp1
	inc $1025
znextp1	lda $5801
	if smalend
	sta $1014
	bit $1024
	else
	sta $1024
	bit $1014
	endif
	; Skip the short description
	lda $5801
	sec
	rol a
	bcc znextp2
	inc $1024
	clc
znextp2	adc <$14
	sta $1014
	bcc znextp3
	inc $1024
znextp3	lda $5801
	and #$1F
	bit $1020
	jmp val8
znextp4	propfind #
	lda ptsizt,x
	sec
	adc <$14
	sta $1014
	bcc znextp5
	inc $1024
znextp5	lda $5801
	bit $1020
	and #$1F
	jmp val8

	; *** REMOVE
	def_inst_1op 137
	lda #0
	sta <$12
	; fall through

	; *** MOVE
	def_inst_2op 14
	; Find the LOC of first object, see if need to remove
	ldx <$11
	clc
	lda objadl,x
	adc #4
	sta $1013
	lda objadh,x
	adc #0
	sta $1023
	lda $5801
	ldy <$12
	sty $5801
	tay
	beq zmove2
	; Look at the NEXT slot too
	inc $1013
	bne zmove1
	inc $1023
zmove1	ldy $5801
	ldx #0
	stx $5801
	; Find it in the FIRST-NEXT chain of the parent object
	tax
	lda objadl,x
	adc #6
	sta $1014
	lda objadh,x
	adc #0
	sta $1024
	lax $5801 ; not adjust carry flag
	eor <$11
	bne zmove3
	; It is the first child object
	; Let First(Parent)=Next(Child)
	sty $5801
	jmp zmove2
	; It is not the first child object
zmove3	lda objadl,x
	adc #5
	sta $1014
	lda objadh,x
	adc #0
	sta $1024
	lax $5801
	eor <$11
	bne zmove3
	; It is found
	sty $5801
	; Now insert the object into the new container (if nonzero)
zmove2	ldx <$12
	beq zmove4
	lda objadl,x
	adc #6
	sta $1014
	lda objadh,x
	adc #0
	sta $1024
	ldy $5801
	stx $5801
	bit $1013
	bit $1023
	sty $5801
zmove4	lda $1020
	jmp nxtinst

	; Print a space
space	lda <$30
	cmp #$E2
	bne space1
	lda <$31
	and #$1F
	bne space1
	jsr bufout
	lda <$31
	and #$1F
	bne space2
space1	inc <$31
space2	rts

	; Output and clear the buffer
bufout	lda <$31
	anc #$1F
	adc <$30
	bcc bufout0
	jsr addlin1
bufout0	ldx #0
	lda <$32
	ldy <$31
bufout1	bit $2002
	bpl bufout1
	stx $2001 ; render off
	sta $2006
	sty $2006
	ldx #$E2
	cpx <$30
	beq bufout3
bufout2	lda <0,x
	sta $2007
	inx
	cpx <$30
	bne bufout2
bufout3	tya
	anc #$1F
	bne bufout4
	; Blank the bottom row (just scrolled in)
	lda <5
	sta $2006
	lda <4
	sta $2006
	lda #32
	sta $2007 ;1
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007 ;10
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007 ;20
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007 ;30
bufout4	lda #$F8
	sta $2005
	ldx <$33
	stx $2005
	anc #$08
	sta $2001
	sta $2000
	lda <$30
	sbc #$E1
	clc
	adc <$31
	sta <$31
	lda <$32
	adc #0
	sta <$32
	lda #$E2
	sta <$30
bufout5	rts

	; Skip to the next line
addline	sec
addlin1	lda <$33
	adc #7
	sta <$33
	cmp #$F0
	bcc addlin2
	anc #0
	sta <$33
addlin2	lda <$31
	and #$E0
	adc #$20
	sta <$31
	lda <$32
	adc #0
	sta <$32
	cmp #$27
	bne addlin3
	lda <$31
	cmp #$C0
	bne addlin3
	lda #$24
	sta <$32
	lda #0
	sta <$31
	; Prepare address to blank out the line
addlin3	lax <$31
	clc
	adc #$40
	sta <4
	lda <$32
	adc #0
	sta <5
	cmp #$27
	bcc addlin4
	cpx #$80
	bcc addlin4
	lda #$24
	sax <4
	sta <5
addlin4	dec <$34
	bne addlin5
	lda #27
	sta <$34
	jmp more
addlin5	rts

	; Display the <MORE> prompt
more	ldx #0
	lda <$32
	ldy <$31
more1	bit $2002
	bpl more1
	stx $2001 ; render off
	sta $2006
	sty $2006
	lda #'<'
	sta $2007
	lda #'M'
	sta $2007
	lda #'O'
	sta $2007
	lda #'R'
	sta $2007
	lda #'E'
	sta $2007
	lda #'>'
	sta $2007
	; Blank the bottom row (just scrolled in)
	lda <5
	sta $2006
	lda <4
	sta $2006
	lda #32
	sta $2007 ;1
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007 ;10
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007 ;20
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007 ;30
	; Re-enable rendering
	lda #$F8
	sta $2005
	ldx <$33
	stx $2005
	anc #$08
	sta $2001
	sta $2000
	; Wait for keyboard not pushed
more2	ldx #5
	stx $4016
	dex
	ldy #9
more3	stx $4016
	lda $4017
	ora #$E1
	eor #$FF
	bne more2
	lda #6
	sta $4016
	lda $4017
	ora #$E1
	eor #$FF
	bne more2
	dey
	bne more3
	; Wait for space-bar pushed
	ldx #5
	lda #4
	ldy #6
more4	stx $4016 ;reset
	sta $4016 ;0/0
	sty $4016 ;0/1
	sta $4016 ;1/0
	sty $4016 ;1/1
	sta $4016 ;2/0
	sty $4016 ;2/1
	sta $4016 ;3/0
	sty $4016 ;3/1
	sta $4016 ;4/0
	sty $4016 ;4/1
	sta $4016 ;5/0
	sty $4016 ;5/1
	sta $4016 ;6/0
	sty $4016 ;6/1
	sta $4016 ;7/0
	sty $4016 ;7/1
	sta $4016 ;8/0
	sty $4016 ;8/1
	and $4017
	bne more4
	; Erase <MORE>
	lda #0
	sta $2001
	lda <$32
	sta $2006
	lda <$31
	sta $2006
	lda #32
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	sta $2007
	rts

	; *** PRINTC
	def_inst_ext 229
	lda <$11
	beq zprntc2
	cmp #32
	beq zprntc1
	cmp #13
	beq zcrlf
	ldx <$30
	beq zprntc2
	sta <0,x
	inc <$30
zprntc1	jmp nxtinst
zprntc2	jsr space
	jmp nxtinst

	; *** CRLF
	def_inst_0op 187
zcrlf	jsr bufout
	lda <$31
	ora #$1F
	sta <$31
zcrlf2	jmp nxtinst

	; *** PRINTN
	def_inst_ext 230
	lda <$30
	beq zcrlf2 ; ensure there is room in the buffer
	ldy <$11
	lax <$21
	anc #$FF
	bcc znum01
	eor #$FF
	sta <4
	ldx <$30
	inc <$30
	lda #'-'
	sta <0,x
	tya
	eor #$FF
	tay
	ldx <4
znum01	lda digit0l,y
	adc digit0h,x
	pha
	cmp #10
	lda digit1l,y
	adc digit1h,x
	pha
	cmp #10
	lda digit2l,y
	adc digit2h,x
	pha
	cmp #10
	lda #0
	adc digit3h,x
	pha
	cmp #10
	lda #0
	adc digit4h,x
	ldx <$30
	tay ; make the flag according to accumulator
	beq znum02
	; Five digits
	sta <0,x
	pla
	sta 1,x
	pla
	sta 2,x
	pla
	sta 3,x
	pla
	sta 4,x
	txa
	axs #-5
	stx <$30
	jmp nxtinst
znum02	pla
	beq znum03
	; Four digits
	sta <0,x
	pla
	sta 1,x
	pla
	sta 2,x
	pla
	sta 3,x
	txa
	axs #-4
	stx <$30
	jmp nxtinst
znum03	pla
	beq znum04
	; Three digits
	sta <0,x
	pla
	sta 1,x
	pla
	sta 2,x
	txa
	axs #-3
	stx <$30
	jmp nxtinst
znum04	pla
	beq znum05
	; Two digits
	sta <0,x
	inx
	pla
	sta <0,x
	inx
	stx <$30
	jmp nxtinst
znum05	pla
	; One digit
	sta <0,x
	inc <$30
	jmp nxtinst

	; *** PRINTI
	def_inst_0op 178
	jsr textpc
	jmp nxtinst

	; *** PRINTR
	def_inst_0op 179
	jsr textpc
	jsr bufout
	lda <$31
	ora #$1F
	sta <$31
	lda #1
	jmp ret8

	; *** PRINTB
	def_inst_1op 135
	jsr textba
	jmp nxtinst

	; *** PRINT
	def_inst_1op 141
	asl <$11
	rol <$21
	lda #0
	rol a
	sta <$36
	jsr textwa
	jmp nxtinst

	; *** PRINTD
	def_inst_1op 138
	ldx <$11
	clc
	lda objadl,x
	adc #7
	sta $1012
	lda objadh,x
	adc #0
	sta $1022
	if smalend
	lda $5801
	else
	ldy $5801
	endif
	inc $1012
	bne zprntd1
	inc $1022
zprntd1	if smalend
	adc #1
	sta <$11
	lda $5801
	else
	lda $5801
	adc #1
	sta <$11
	tya
	endif
	adc #0
	sta <$21
	jsr textba
	jmp nxtinst

	; *** VERIFY
	def_inst_0op 189
	jmp tpredic ; there is no disk, so just assume it is OK

	; *** QUIT
	def_inst_0op 186
	jsr bufout
	lda <$31
	ora #$1F
	sta <$31
	jsr bufout
zquit	jmp zquit

	; *** READ
	jsr bufout
	;TODO
zread	jmp zread

	bank intbank+3
	; Z-character decoding
	; high 3-bits = state, low 5-bits = value

	org $F100-12
	; Text starting from program counter
textpc	lda #0
	sta <$38
	sta <$27
	ldx #$A0
	stx <$09
	stx <$0A

	org $F100
	lda <$27
	bmi textpc1
	lda #$F2
	sta <$39
	lda #$FE
	pha
	fetch_pc y,lda
	if smalend
	sta <$17
	else
	sta <$27
	endif
	if smalend
	fetch_pc y,lda
	sta <$27
	else
	fetch_pc y,ldx
	stx <$17
	endif
	lsr a
	lsr a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
textpc1	rts

	org $F200
	lda #$FE
	pha
	inc <$39
	ldx <$17
	stx <4
	lda <$27
	asl <4
	rol a
	asl <4
	rol a
	asl <4
	rol a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $F300
	lda #$F1
	sta <$39
	lda #$FE
	pha
	lda <$17
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $F400-12
	; Text from byte address
textba	lda #0
	sta <$38
	sta <$27
	ldx #$A0
	stx <$09
	stx <$0A

	org $F400
	lda <$27
	bmi textba1
	lda #$F5
	sta <$39
	lda #$FE
	pha
	lda $1011
	lda $1021
	lda $5803
	if smalend
	sta <$17
	else
	sta <$27
	endif
	inc $1011
	bne textba2
	inc $1021
textba2	if smalend
	lda $5803
	sta <$27
	else
	ldx $5803
	stx <$17
	endif
	inc $1011
	bne textba3
	inc $1021
textba3	lsr a
	lsr a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts
textba1	bit $1020
	rts

	org $F500
	lda #$FE
	pha
	inc <$39
	ldx <$17
	stx <4
	lda <$27
	asl <4
	rol a
	asl <4
	rol a
	asl <4
	rol a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $F600
	lda #$F4
	sta <$39
	lda #$FE
	pha
	lda <$17
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $F700-12
	; Text from word address (aligned)
textwa	lda #0
	sta <$38
	sta <$27
	ldx #$A0
	stx <$09
	stx <$0A

	org $F700
	lda <$27
	bmi textwa1
	lda #$F8
	sta <$39
	lda #$FE
	pha
	lda $1011
	lda $1021
	ldy <$36
	lda $5803,y
	if smalend
	sta <$17
	else
	sta <$27
	endif
	if smalend
	inc $1011
	lda $5803,y
	sta <$27
	else
	ldx $5803,y
	stx <$17
	endif
	inc $1011
	bne textwa4
	inc $1021
	bne textwa4
	inc <$36
textwa4	lsr a
	lsr a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts
textwa1	bit $1020
	rts

	org $F800
	lda #$FE
	pha
	inc <$39
	ldx <$17
	stx <4
	lda <$27
	asl <4
	rol a
	asl <4
	rol a
	asl <4
	rol a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $F900
	lda #$F7
	sta <$39
	lda #$FE
	pha
	lda <$17
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $FA00-20
	; Text from frequent word
textfw	lda #0
	sta <$38
	sta <$29
	lda <$0A
	sta <$0B
	ldx #$A0
	stx <$09
	stx <$0A
	lda <$39
	sta <$35

	org $FA00
	lda <$29
	bmi textfw1
	lda #$FB
	sta <$39
	lda #$FE
	pha
	ldy <$37
	lda $5803,y
	if smalend
	sta <$19
	else
	sta <$29
	endif
	inc $1016
	if smalend
	lda $5803,y
	sta <$29
	else
	ldx $5803,y
	stx <$19
	endif
	inc $1016
	bne textfw2
	inc $1026
	bne textfw2
	inc <$37
textfw2	lsr a
	lsr a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts
textfw1	bit $1020
	lda <$35
	sta <$39
	lda <$0B
	sta <$0A
	sta <$09
	jmp [$38]

	org $FB00
	lda #$FE
	pha
	inc <$39
	ldx <$19
	stx <4
	lda <$29
	asl <4
	rol a
	asl <4
	rol a
	asl <4
	rol a
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	org $FC00
	lda #$FA
	sta <$39
	lda #$FE
	pha
	lda <$19
	anc #31
	ora <$09
	tax
	lda zchad,x
	pha
	rts

	; States can be:
	;   0   = Second step of ASCII escape
	;   1-3 = Fwords
	;   4   = First step of ASCII escape
	;   5-7 = Shift states 0,1,2

	; These subroutines are entered with X set to the state.
	; Also has carry flag cleared.
	org $FE01

	; ** Emit a space
	def_zchars $A0
	def_zchars $C0
	def_zchars $E0
zch32	jsr space
	jmp [$38]

	; ** Second escape
	def_zchars $00,$1F
	txa
	ora <5
	beq zch1
	cmp #32
	beq zch32
	cmp #13
	beq zch13
	ldx <$30
	beq zch1
	sta <0,x
	inc <$30
	lda <$0A
	sta <$09
	jmp [$38]

	; ** First escape
	def_zchars $80,$9F
	txa
	asl a
	asl a
	asl a
	asl a
	asl a
	sta <5
	anc #0
	sta <$09
	jmp [$38]

	; ** Frequent words
	def_zchars $20,$7F
	lda fwordsl,x
	sta $1015
	lda fwordsh,x
	sta $1025
	lda $5801
	if smalend
	asl a
	sta <$16
	else
	sta <$26
	lda #0
	rol a
	sta <$37
	endif
	inc $1015
	bne zfw1
	inc $1025
zfw1	lda $5801
	if smalend
	rol a
	sta <$26
	else
	asl a
	sta <$16
	rol <$26
	endif
	lda #0
	adc #0
	sta <$37
	jmp textfw

	; ** Begin escape
	def_zchars $E6
	lda #$80
	sta <$09
	jmp [$38]

	; ** Direct character code
	def_zchars $A6,$BF
	def_zchars $C6,$DF
	def_zchars $E8,$FF
	ldy <$30
	beq zch1
	stx <$E0,y
	inc <$30
zch1	lda <$0A
	sta <$09
	jmp [$38]

	; ** Emit a line break
	def_zchars $E7
zch13	jsr bufout
	lda <$31
	ora #$1F
	sta <$31
	lda <$0A
	sta <$09
	jmp [$38]

	; ** Begin frequent words state 0-31
	def_zchars $A1
	def_zchars $C1
	def_zchars $E1
	lda #$20
	sta <$09
	jmp [$38]

	; ** Begin frequent words state 32-63
	def_zchars $A2
	def_zchars $C2
	def_zchars $E2
	lda #$40
	sta <$09
	jmp [$38]

	; ** Begin frequent words state 64-95
	def_zchars $A3
	def_zchars $C3
	def_zchars $E3
	lda #$60
	sta <$09
	jmp [$38]

	; ** Temporary shift 1
	def_zchars $A4
	lda #$C0
	sta <$09
	jmp [$38]

	; ** Temporary shift 2
	def_zchars $A5
	lda #$E0
	sta <$09
	jmp [$38]

	; ** Permanent shift 1 or 2
	def_zchars $C4
	def_zchars $E5
	and #$F0
	sta <$0A
	jmp [$38]

	; ** Permanent shift 0
	def_zchars $C5
	def_zchars $E4
	lda #$A0
	sta <$09
	sta <$0A
	jmp [$38]

	; Reset vector
	bank intbank+3
	org $FFFA
	dw 0,reset,0

	; Pattern tables
	bank intbank+4
	org $0000
	incbin "pc.chr"

	; Cursor icon
	org $07F0
	defchr $00000000, \
	       $03030300, \
	       $00303030, \
	       $03030300, \
	       $00303030, \
	       $03030300, \
	       $00303030, \
	       $00000000

	; Postprocessor
	emu

	org $0000
	lda 0
	sta $2012
	inc <1
	rts

	org $0040
	db "0123456789012345"
	db "6789012345678901"

	org $0080
	db "                                "   ; $80-$9F
	db "      abcdefghijklmnopqrstuvwxyz"   ; $A0-$BF
	db "      ABCDEFGHIJKLMNOPQRSTUVWXYZ"   ; $C0-$DF
	db "      **0123456789.,!?_#'\"/\\-:()" ; $E0-$FF

	org $8000
	cld

	; Make duplicates of ASCII characters as Z-characters
	lda #1
	sta $200D
	lda #0
	sta $200E
	lda #8
	sta $200F
	ldx #$80
pp1	lda #4
	sta <2
	lda <0,x
	asl a
	rol <2
	asl a
	rol <2
	asl a
	rol <2
	asl a
	rol <2
	sta <1
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	inx
	bne pp1

	; Make duplicate of digits for use with PRINTN
	ldx #0
	stx $200E
	stx $200F
pp2	lda #4
	sta <2
	lda <$40,x
	asl a
	rol <2
	asl a
	rol <2
	asl a
	rol <2
	asl a
	rol <2
	sta <1
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	jsr 0
	inx
	cpx #32
	bne pp2

	; Finished
	hlt

	org $FFFC
	dw $8000

	code
	bank intbank+4

C program

This program is generating a stub file and story ROM for its use. 

/*
  This file is part of Famizork II and is in the public domain.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static FILE*fp;
static int c;
static int d;
static int gamesize;
static char endian;
static unsigned char mem[0x20000];
static char buf[256];

#define OUTHEADER(x,y) fprintf(fp,"%s\t= %u\n",x,(mem[y*2+endian]<<8)|mem[y*2+1-endian])

int main(int argc,char**argv) {
  if(argc<2) return 1;
  fp=fopen(argv[1],"rb");
  fseek(fp,0,SEEK_END);
  gamesize=ftell(fp);
  if(gamesize>0x20000 || gamesize<0) return 1;
  fseek(fp,0,SEEK_SET);
  fread(mem,1,gamesize,fp);
  fclose(fp);
  if(*mem!=3) return 1;
  sprintf(buf,"%s.asm",argv[1]);
  fp=fopen(buf,"w");
  endian=mem[1]&1;
  mem[1]&=3;
  mem[1]|=16;
  c=(gamesize>0x10000?16:gamesize>0x8000?8:gamesize>0x4000?4:2);
  fprintf(fp,"\tnes2prgram 0,131072\n");
  fprintf(fp,"\tinesprg %d\n",(c>>1)+2);
  fprintf(fp,"intbank\t= %d\n",c);
  fprintf(fp,"smalend\t= %d\n",endian);
  fprintf(fp,"large\t= %d\n",gamesize>=0x10000);
  if(gamesize<0x10000) fprintf(fp,"maxaddr\t= %u\n",gamesize-1);
  OUTHEADER("start",3);
  OUTHEADER("vocab",4);
  OUTHEADER("object",5);
  OUTHEADER("global",6);
  OUTHEADER("purbot",7);
  OUTHEADER("fwords",12);
  fprintf(fp,"\tcode\n\tbank 0\n\tincbin \"%s.rom\"\n\tinclude \"famizork2.asm\"\n",argv[1]);
  fprintf(fp,"\n\tbank %d\n\torg fwordsl\n",c);
  d=(mem[24+endian]<<8)|mem[25-endian];
  for(c=0;c<192;c+=2) fprintf(fp,"\tdb %d\n",(d+c)&255);
  for(c=0;c<192;c+=2) fprintf(fp,"\tdb %d\n",((d+c)>>8)&255);
  fprintf(fp,"\torg multabl\n");
  for(c=0;c<255;c++) fprintf(fp,"\tdb %d\n",((c*c)>>2)&255);
  for(c=0;c<512;c++) fprintf(fp,"\tdb %d\n",((c*c)>>10)&255);
  fprintf(fp,"\tbank intbank+4\n");
  fclose(fp);
  sprintf(buf,"%s.rom",argv[1]);
  fp=fopen(buf,"wb");
  if(gamesize>0x10000) {
    fwrite(mem+0x10000,1,0x10000,fp);
    fwrite(mem,1,0x10000,fp);
  } else {
    fwrite(mem,1,gamesize,fp);
  }
  fclose(fp);
  return 0;
}

Explanation

The explanation of the mapper is User:Zzo38/Mapper_I.

The pattern table is arranged in this way (although $7F is the cursor picture, not shown here): 

0123456789012345
6789012345678901
 !"#$%&'()*+,-./
0123456789:;<=>?
@ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]^_
`abcdefghijklmno
pqrstuvwxyz{|}~
                
                
      abcdefghij
klmnopqrstuvwxyz
      ABCDEFGHIJ
KLMNOPQRSTUVWXYZ
      **01234567
89.,!?_#'"/\-:()

As you can see there are many duplicates, in particular each digit occurs five times, except 0 and 1 which occur six times each. Many other characters also occur twice. These will improve the speed of the program, since it does not have to convert Z-characters and numbers into ASCII before displaying them.

Many things are precomputed at compile-time in order to improve speed (also improves size of the interpreter):

  • The mode byte is set to indicate that the status bar is unavailable
  • Address of objects, global variables, and frequent words table
  • Starting address of execution of program
  • Endianness and various calculations related to it
  • The size of the story file, which can be used to determine needed ROM sizes and optimizing of the interpreter
  • Self-inserting-breaks
  • Stuff to optimize the vocabulary (not yet)
  • Multiplication tables

A custom mapper is used, which bankswitches only one byte at a time. This makes much of the logic for addressing the story file much simpler than it otherwise would be. It also overlaps bankswitching registers with mirrors of the RAM internal to the console, and since they respond to multiple addresses, this means you can save the bankswitched value at the same time as bankswitching, that you can store multiple bank numbers at once (even though the mapper can only remember one at once), and that reading from the RAM mirrors will also bankswitch (allows you to restore a saved bankswitch in four cycles; with other mappers it is usually seven).

There is an instruction decoding table, which is one table for all instructions and contains duplicates for the different forms of the instruction (such as EXT forms of 2OP instructions, the different variable/immediate combinations for 2OP, and the different operand types for 1OP). However, a different opcode is used when EQUAL? is encoded as EXT than as 2OP, in order to improve the speed in the 2OP case. The code can just use "jmp nxtinst" to begin decoding the next instruction; it doesn't use return from subroutine.

Instruction decoding tables, as well as the Z-character decoding tables, both use the RTS trick, although in the case of Z-character decoding, the table contains only the low byte of the address since the code is small enough in this case.

Also it is using several stable unofficial opcodes.

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