Ophis/doc/samplecode.sgm
2014-05-24 05:48:26 -07:00

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<appendix>
<title>Example Programs</title>
<para>
This Appendix collects all the programs referred to in the course
of this manual.
</para>
<section id="tutor1-src">
<title id="tutor1-fname"><filename>hello1.oph</filename></title>
<programlisting>
.word $0801
.org $0801
.outfile "hello.prg"
.word next, 10 ; Next line and current line number
.byte $9e," 2064",0 ; SYS 2064
next: .word 0 ; End of program
.advance 2064
ldx #0
loop: lda hello, x
beq done
jsr $ffd2
inx
bne loop
done: rts
hello: .byte "HELLO, WORLD!", 0
</programlisting>
</section>
<section id="tutor2-src">
<title id="tutor2-fname"><filename>hello2.oph</filename></title>
<programlisting>
.word $0801
.org $0801
.outfile "hello.prg"
.scope
.word _next, 10 ; Next line and current line number
.byte $9e," 2064",0 ; SYS 2064
_next: .word 0 ; End of program
.scend
.advance 2064
.alias chrout $ffd2
ldx #0
* lda hello, x
beq +
jsr chrout
inx
bne -
* rts
hello: .byte "HELLO, WORLD!", 0
</programlisting>
</section>
<section id="c64-1-src">
<title id="c64-1-fname"><filename>c64-1.oph</filename></title>
<programlisting>
.word $0801
.org $0801
.scope
.word _next, 10 ; Next line and current line number
.byte $9e," 2064",0 ; SYS 2064
_next: .word 0 ; End of program
.scend
.advance 2064
.require "../platform/c64kernal.oph"
</programlisting>
</section>
<section id="kernal-src">
<title id="kernal-fname"><filename>c64kernal.oph</filename></title>
<programlisting>
; KERNAL routine aliases (C64)
.alias acptr $ffa5
.alias chkin $ffc6
.alias chkout $ffc9
.alias chrin $ffcf
.alias chrout $ffd2
.alias ciout $ffa8
.alias cint $ff81
.alias clall $ffe7
.alias close $ffc3
.alias clrchn $ffcc
.alias getin $ffe4
.alias iobase $fff3
.alias ioinit $ff84
.alias listen $ffb1
.alias load $ffd5
.alias membot $ff9c
.alias memtop $ff99
.alias open $ffc0
.alias plot $fff0
.alias ramtas $ff87
.alias rdtim $ffde
.alias readst $ffb7
.alias restor $ff8a
.alias save $ffd8
.alias scnkey $ff9f
.alias screen $ffed
.alias second $ff93
.alias setlfs $ffba
.alias setmsg $ff90
.alias setnam $ffbd
.alias settim $ffdb
.alias settmo $ffa2
.alias stop $ffe1
.alias talk $ffb4
.alias tksa $ff96
.alias udtim $ffea
.alias unlsn $ffae
.alias untlk $ffab
.alias vector $ff8d
; Character codes for the colors.
.alias color'0 144
.alias color'1 5
.alias color'2 28
.alias color'3 159
.alias color'4 156
.alias color'5 30
.alias color'6 31
.alias color'7 158
.alias color'8 129
.alias color'9 149
.alias color'10 150
.alias color'11 151
.alias color'12 152
.alias color'13 153
.alias color'14 154
.alias color'15 155
; ...and reverse video
.alias reverse'on 18
.alias reverse'off 146
; ...and character set
.alias upper'case 142
.alias lower'case 14
</programlisting>
</section>
<section id="tutor3-src">
<title id="tutor3-fname"><filename>hello3.oph</filename></title>
<programlisting>
.include "c64-1.oph"
.outfile "hello.prg"
.macro print
ldx #0
_loop: lda _1, x
beq _done
jsr chrout
inx
bne _loop
_done:
.macend
.macro greet
`print hello1
`print _1
`print hello2
.macend
lda #147
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
rts
hello1: .byte "HELLO, ",0
hello2: .byte "!", 13, 0
target1: .byte "PROGRAMMER", 0
target2: .byte "ROOM", 0
target3: .byte "BUILDING", 0
target4: .byte "NEIGHBORHOOD", 0
target5: .byte "CITY", 0
target6: .byte "NATION", 0
target7: .byte "WORLD", 0
target8: .byte "SOLAR SYSTEM", 0
target9: .byte "GALAXY", 0
target10: .byte "UNIVERSE", 0
</programlisting>
</section>
<section id="tutor4a-src">
<title id="tutor4a-fname"><filename>hello4a.oph</filename></title>
<programlisting>
.include "c64-1.oph"
.outfile "hello.prg"
.macro print
ldx #0
_loop: lda _1, x
beq _done
jsr chrout
inx
bne _loop
_done:
.macend
.macro greet
lda #30
jsr delay
`print hello1
`print _1
`print hello2
.macend
lda #147
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
rts
hello1: .byte "HELLO, ",0
hello2: .byte "!", 13, 0
target1: .byte "PROGRAMMER", 0
target2: .byte "ROOM", 0
target3: .byte "BUILDING", 0
target4: .byte "NEIGHBORHOOD", 0
target5: .byte "CITY", 0
target6: .byte "NATION", 0
target7: .byte "WORLD", 0
target8: .byte "SOLAR SYSTEM", 0
target9: .byte "GALAXY", 0
target10: .byte "UNIVERSE", 0
; DELAY routine. Executes 2,560*(A) NOP statements.
delay: tax
ldy #00
* nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
iny
bne -
dex
bne -
rts
</programlisting>
</section>
<section id="tutor4b-src">
<title id="tutor4b-fname"><filename>hello4b.oph</filename></title>
<programlisting>
.include "c64-1.oph"
.outfile "hello.prg"
.macro print
ldx #0
_loop: lda _1, x
beq _done
jsr chrout
inx
bne _loop
_done:
.macend
.macro greet
lda #30
jsr delay
`print hello1
`print _1
`print hello2
.macend
lda #147
jsr chrout
lda #lower'case
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
rts
hello1: .byte "Hello, ",0
hello2: .byte "!", 13, 0
target1: .byte "programmer", 0
target2: .byte "room", 0
target3: .byte "building", 0
target4: .byte "neighborhood", 0
target5: .byte "city", 0
target6: .byte "nation", 0
target7: .byte "world", 0
target8: .byte "Solar System", 0
target9: .byte "Galaxy", 0
target10: .byte "Universe", 0
; DELAY routine. Executes 2,560*(A) NOP statements.
delay: tax
ldy #00
* nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
iny
bne -
dex
bne -
rts
</programlisting>
</section>
<section id="tutor4c-src">
<title id="tutor4c-fname"><filename>hello4c.oph</filename></title>
<programlisting>
.include "c64-1.oph"
.outfile "hello.prg"
.macro print
ldx #0
_loop: lda _1, x
beq _done
jsr chrout
inx
bne _loop
_done:
.macend
.macro greet
lda #30
jsr delay
`print hello1
`print _1
`print hello2
.macend
lda #147
jsr chrout
lda #lower'case
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
rts
.charmap 'A, "abcdefghijklmnopqrstuvwxyz"
.charmap 'a, "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
hello1: .byte "Hello, ",0
hello2: .byte "!", 13, 0
target1: .byte "programmer", 0
target2: .byte "room", 0
target3: .byte "building", 0
target4: .byte "neighborhood", 0
target5: .byte "city", 0
target6: .byte "nation", 0
target7: .byte "world", 0
target8: .byte "Solar System", 0
target9: .byte "Galaxy", 0
target10: .byte "Universe", 0
; DELAY routine. Executes 2,560*(A) NOP statements.
delay: tax
ldy #00
* nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
iny
bne -
dex
bne -
rts
</programlisting>
</section>
<section id="tutor5-src">
<title id="tutor5-fname"><filename>hello5.oph</filename></title>
<programlisting>
.include "c64-1.oph"
.outfile "hello.prg"
.data
.org $C000
.text
.macro print
ldx #0
_loop: lda _1, x
beq _done
jsr chrout
inx
bne _loop
_done:
.macend
.macro greet
lda #30
jsr delay
`print hello1
`print _1
`print hello2
.macend
lda #147
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
rts
hello1: .byte "HELLO, ",0
hello2: .byte "!", 13, 0
target1: .byte "PROGRAMMER", 0
target2: .byte "ROOM", 0
target3: .byte "BUILDING", 0
target4: .byte "NEIGHBORHOOD", 0
target5: .byte "CITY", 0
target6: .byte "NATION", 0
target7: .byte "WORLD", 0
target8: .byte "SOLAR SYSTEM", 0
target9: .byte "GALAXY", 0
target10: .byte "UNIVERSE", 0
; DELAY routine. Takes values from the Accumulator and pauses
; for that many jiffies (1/60th of a second).
.scope
.data
.space _tmp 1
.space _target 1
.text
delay: sta _tmp ; save argument (rdtim destroys it)
jsr rdtim
clc
adc _tmp ; add current time to get target
sta _target
* jsr rdtim
cmp _target
bmi - ; Buzz until target reached
rts
.scend
.checkpc $A000
.data
.checkpc $D000
</programlisting>
</section>
<section id="tutor6-src">
<title id="tutor6-fname"><filename>hello6.oph</filename></title>
<programlisting>
.include "c64-1.oph"
.outfile "hello.prg"
.data
.org $C000
.space cache 2
.text
.macro print
lda #<_1
ldx #>_1
jsr printstr
.macend
.macro greet
lda #30
jsr delay
`print hello1
`print _1
`print hello2
.macend
; Save the zero page locations that PRINTSTR uses.
lda $10
sta cache
lda $11
sta cache+1
lda #147
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
; Restore the zero page values printstr uses.
lda cache
sta $10
lda cache+1
sta $11
rts
hello1: .byte "HELLO, ",0
hello2: .byte "!", 13, 0
target1: .byte "PROGRAMMER", 0
target2: .byte "ROOM", 0
target3: .byte "BUILDING", 0
target4: .byte "NEIGHBORHOOD", 0
target5: .byte "CITY", 0
target6: .byte "NATION", 0
target7: .byte "WORLD", 0
target8: .byte "SOLAR SYSTEM", 0
target9: .byte "GALAXY", 0
target10: .byte "UNIVERSE", 0
; DELAY routine. Takes values from the Accumulator and pauses
; for that many jiffies (1/60th of a second).
.scope
.data
.space _tmp 1
.space _target 1
.text
delay: sta _tmp ; save argument (rdtim destroys it)
jsr rdtim
clc
adc _tmp ; add current time to get target
sta _target
* jsr rdtim
cmp _target
bmi - ; Buzz until target reached
rts
.scend
; PRINTSTR routine. Accumulator stores the low byte of the address,
; X register stores the high byte. Destroys the values of $10 and
; $11.
.scope
printstr:
sta $10
stx $11
ldy #$00
_lp: lda ($10),y
beq _done
jsr chrout
iny
bne _lp
_done: rts
.scend
.checkpc $A000
.data
.checkpc $D000
</programlisting>
</section>
<section id="tutor7-src">
<title id="tutor7-fname"><filename>hello7.oph</filename></title>
<programlisting>
.include "../platform/c64_0.oph"
.require "../platform/c64kernal.oph"
.outfile "hello.prg"
.data
.org $C000
.text
.macro print
lda #<_1
ldx #>_1
jsr printstr
.macend
.macro greet
lda #30
jsr delay
`print hello1
`print _1
`print hello2
.macend
lda #147
jsr chrout
`greet target1
`greet target2
`greet target3
`greet target4
`greet target5
`greet target6
`greet target7
`greet target8
`greet target9
`greet target10
rts
hello1: .byte "HELLO, ",0
hello2: .byte "!", 13, 0
target1: .byte "PROGRAMMER", 0
target2: .byte "ROOM", 0
target3: .byte "BUILDING", 0
target4: .byte "NEIGHBORHOOD", 0
target5: .byte "CITY", 0
target6: .byte "NATION", 0
target7: .byte "WORLD", 0
target8: .byte "SOLAR SYSTEM", 0
target9: .byte "GALAXY", 0
target10: .byte "UNIVERSE", 0
; DELAY routine. Takes values from the Accumulator and pauses
; for that many jiffies (1/60th of a second).
.scope
.data
.space _tmp 1
.space _target 1
.text
delay: sta _tmp ; save argument (rdtim destroys it)
jsr rdtim
clc
adc _tmp ; add current time to get target
sta _target
* jsr rdtim
cmp _target
bmi - ; Buzz until target reached
rts
.scend
; PRINTSTR routine. Accumulator stores the low byte of the address,
; X register stores the high byte. Destroys the values of $10 and
; $11.
.scope
.data zp
.space _ptr 2
.text
printstr:
sta _ptr
stx _ptr+1
ldy #$00
_lp: lda (_ptr),y
beq _done
jsr chrout
iny
bne _lp
_done: rts
.scend
.checkpc $A000
.data
.checkpc $D000
.data zp
.checkpc $80
</programlisting>
</section>
<section id="structure-src">
<title id="structure-fname"><filename>structuredemo.oph</filename></title>
<programlisting>
.include "../platform/c64_0.oph"
.require "../platform/c64kernal.oph"
.outfile "structuredemo.prg"
jsr print'unsorted
jsr insertion'sort
jsr print'list
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Linked list data: head, next, lb, hb.
; lb/hb: Low/high bytes of the data array. These are immutable and
; kept with the program text.
; head: Array index of the first element in the list, or #$FF if the
; list is empty
; next: Array of successor indices. If you've just read element X,
; the value of memory location next+X is the index of the
; next element. If next is #$FF, you've reached the end of
; the list.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
.data
.org $C000
.space head 1
.space next 16
.text
lb: .byte &lt;$838,&lt;$618,&lt;$205,&lt;$984,&lt;$724,&lt;$301,&lt;$249,&lt;$946
.byte &lt;$925,&lt;$043,&lt;$114,&lt;$697,&lt;$985,&lt;$633,&lt;$312,&lt;$086
hb: .byte &gt;$838,&gt;$618,&gt;$205,&gt;$984,&gt;$724,&gt;$301,&gt;$249,&gt;$946
.byte &gt;$925,&gt;$043,&gt;$114,&gt;$697,&gt;$985,&gt;$633,&gt;$312,&gt;$086
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; insertion'sort: Sorts the list defined by head, next, hb, lb.
; Arguments: None.
; Modifies: All registers destroyed, head and next array sorted.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
insertion'sort:
lda #$FF ; Clear list by storing the terminator in 'head'
sta head
ldx #$0 ; Loop through the lb/hb array, adding each
insertion'sort'loop: ; element one at a time
txa
pha
jsr insert_elt
pla
tax
inx
cpx #$10
bne insertion'sort'loop
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; insert_elt: Insert an element into the linked list. Maintains the
; list in sorted, ascending order. Used by
; insertion'sort.
; Arguments: X register holds the index of the element to add.
; Modifies: All registers destroyed; head and next arrays updated
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
.data
.space lbtoinsert 1
.space hbtoinsert 1
.space indextoinsert 1
.text
insert_elt:
ldy head ; If the list is empty, make
cpy #$FF ; head point at it, and return.
bne insert_elt'list'not'empty
stx head
tya
sta next,x
rts
insert_elt'list'not'empty:
lda lb,x ; Cache the data we're inserting
sta lbtoinsert
lda hb,x
sta hbtoinsert
stx indextoinsert
ldy head ; Compare the first value with
sec ; the data. If the data must
lda lb,y ; be inserted at the front...
sbc lbtoinsert
lda hb,y
sbc hbtoinsert
bmi insert_elt'not'smallest
tya ; Set its next pointer to the
sta next,x ; old head, update the head
stx head ; pointer, and return.
rts
insert_elt'not'smallest:
ldx head
insert_elt'loop: ; At this point, we know that
lda next,x ; argument &gt; data[X].
tay
cpy #$FF ; if next[X] = #$FF, insert arg at end.
beq insert_elt'insert'after'current
lda lb,y ; Otherwise, compare arg to
sec ; data[next[X]]. If we insert
sbc lbtoinsert ; before that...
lda hb,y
sbc hbtoinsert
bmi insert_elt'goto'next
insert_elt'insert'after'current: ; Fix up all the next links
tya
ldy indextoinsert
sta next,y
tya
sta next,x
rts ; and return.
insert_elt'goto'next: ; Otherwise, let X = next[X]
tya ; and go looping again.
tax
jmp insert_elt'loop
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; print'unsorted: Steps through the data array and prints each value.
; Standalone procedure.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
print'unsorted:
lda #&lt;unsorted'hdr
ldx #&gt;unsorted'hdr
jsr put'string
ldy #$00
print'unsorted'loop:
lda hb, Y
jsr print'hex
lda lb, y
jsr print'hex
lda #$20
jsr chrout
iny
cpy #$10
bne print'unsorted'loop
lda #$0D
jsr chrout
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; print'list: Starts at head, and prints out every value in the
; linked list.
; Standalone procedure.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
print'list:
lda #&lt;sorted'hdr
ldx #&gt;sorted'hdr
jsr put'string
ldy head
print'list'loop:
cpy #$FF
beq print'list'done
lda hb, y
jsr print'hex
lda lb, y
jsr print'hex
lda #$20
jsr chrout
lda next, Y
tay
jmp print'list'loop
print'list'done:
lda #$0d
jsr chrout
rts
;; String data for the above routines.
unsorted'hdr:
.byte 147 ; Clear screen first!
.byte "UNSORTED DATA:",13,0
sorted'hdr:
.byte "SORTED DATA:",13,0
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; print'hex: outputs a two-character hex representation of a one-
; byte value.
; Arguments: Byte to print in accumulator
; Modifies: .A and .X
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
print'hex:
pha
clc
lsr
lsr
lsr
lsr
tax
lda hexstr,x
jsr chrout
pla
and #$0F
tax
lda hexstr,X
jsr chrout
rts
; Character data array for print'hex.
hexstr: .byte "0123456789ABCDEF"
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; put'string: outputs a C-style null terminated string with length
; less than 256 to the screen. If 256 bytes are written
; without finding a terminator, the routine ends quietly.
; Arguments: Low byte of string address in .A, high byte in .X
; Modifies: .A and .Y
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
.data zp
.space put'string'addr 2
.text
put'string:
sta put'string'addr
stx put'string'addr+1
ldy #$00
put'string'loop:
lda (put'string'addr),y
beq put'string'done
jsr chrout
iny
bne put'string'loop
put'string'done:
rts
</programlisting>
</section>
<section id="fib-src">
<title id="fib-fname"><filename>fibonacci.oph</filename></title>
<programlisting>
.include "../platform/c64_0.oph"
.require "../platform/c64kernal.oph"
.outfile "fibonacci.prg"
lda #&lt;opening ; Print opening text
sta fun'args
lda #&gt;opening
sta fun'args+1
jsr print'string
lda #$00
sta fun'vars ; Count num from 0 to 19
* lda fun'vars ; Main loop: print num, with leading space if &lt;10
cmp #$09
bcs +
lda #$20
jsr chrout
lda fun'vars
* sta fun'args ; Copy num to args, print it, plus ": "
inc fun'args
lda #$00
sta fun'args+1
jsr print'dec
lda #$3A
jsr chrout
lda #$20
jsr chrout
lda fun'vars ; Copy num to args, call fib, print result
sta fun'args
jsr fib
jsr print'dec
lda #$0D ; Newline
jsr chrout
inc fun'vars ; Increment num; if it's 20, we're done.
lda fun'vars
cmp #20
bne -- ; Otherwise, loop.
rts
opening:
.byte 147, " FIBONACCI SEQUENCE",13,13,0
.scope
; Uint16 fib (Uint8 x): compute Xth fibonnaci number.
; fib(0) = fib(1) = 1.
; Stack usage: 3.
fib: lda #$03
jsr save'stack
lda fun'vars ; If x &lt; 2, goto _base.
cmp #$02
bcc _base
dec fun'args ; Otherwise, call fib(x-1)...
jsr fib
lda fun'args ; Copy the result to local variable...
sta fun'vars+1
lda fun'args+1
sta fun'vars+2
lda fun'vars ; Call fib(x-2)...
sec
sbc #$02
sta fun'args
jsr fib
clc ; And add the old result to it, leaving it
lda fun'args ; in the 'result' location.
adc fun'vars+1
sta fun'args
lda fun'args+1
adc fun'vars+2
sta fun'args+1
jmp _done ; and then we're done.
_base: ldy #$01 ; In the base case, just copy 1 to the
sty fun'args ; result.
dey
sty fun'args+1
_done: lda #$03
jsr restore'stack
rts
.scend
.scope
; Stack routines: init'stack, save'stack, restore'stack
.data zp
.space _sp $02
.space _counter $01
.space fun'args $10
.space fun'vars $40
.text
init'stack:
lda #$00
sta _sp
lda #$A0
sta _sp+1
rts
save'stack:
sta _counter
sec
lda _sp
sbc _counter
sta _sp
lda _sp+1
sbc #$00
sta _sp+1
ldy #$00
* lda fun'vars, y
sta (_sp), y
lda fun'args, y
sta fun'vars, y
iny
dec _counter
bne -
rts
restore'stack:
pha
sta _counter
ldy #$00
* lda (_sp), y
sta fun'vars, y
iny
dec _counter
bne -
pla
clc
adc _sp
sta _sp
lda _sp+1
adc #$00
sta _sp+1
rts
.scend
; Utility functions. print'dec prints an unsigned 16-bit integer.
; It's ugly and long, mainly because we don't bother with niceties
; like "division". print'string prints a zero-terminated string.
.scope
.data
.org fun'args
.space _val 2
.space _step 2
.space _res 1
.space _allowzero 1
.text
print'dec:
lda #$00
sta _allowzero
lda #&lt;10000
sta _step
lda #&gt;10000
sta _step+1
jsr repsub'16
lda #&lt;1000
sta _step
lda #&gt;1000
sta _step+1
jsr repsub'16
lda #0
sta _step+1
lda #100
sta _step
jsr repsub'16
lda #10
sta _step
jsr repsub'16
lda _val
jsr _print
rts
repsub'16:
lda #$00
sta _res
* lda _val
sec
sbc _step
lda _val+1
sbc _step+1
bcc _done
lda _val
sec
sbc _step
sta _val
lda _val+1
sbc _step+1
sta _val+1
inc _res
jmp -
_done: lda _res
ora _allowzero
beq _ret
sta _allowzero
lda _res
_print: clc
adc #'0
jsr chrout
_ret: rts
.scend
print'string:
ldy #$00
* lda (fun'args), y
beq +
jsr chrout
iny
jmp -
* rts
</programlisting>
</section>
</appendix>