2019-07-25 12:55:10 +00:00
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/*
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2019-07-25 15:26:43 +00:00
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* Find greatest common denominator using subtraction-based Euclidian algorithm
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2019-07-25 12:55:10 +00:00
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* See https://en.wikipedia.org/wiki/Euclidean_algorithm
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* Based on facebook post from
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*/
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2020-12-21 07:57:41 +00:00
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// Commodore 64 PRG executable file
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.file [name="euclid-3.prg", type="prg", segments="Program"]
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.segmentdef Program [segments="Basic, Code, Data"]
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.segmentdef Basic [start=$0801]
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.segmentdef Code [start=$80d]
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.segmentdef Data [startAfter="Code"]
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.segment Basic
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2019-07-25 12:55:10 +00:00
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:BasicUpstart(main)
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2020-06-27 18:32:09 +00:00
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.label print_screen = $400
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2021-09-23 06:24:56 +00:00
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.label print_line_cursor = 5
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.label print_char_cursor = 2
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2020-12-21 07:57:41 +00:00
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.segment Code
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2019-07-25 12:55:10 +00:00
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main: {
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2020-02-23 08:44:36 +00:00
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// print_cls()
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2019-07-25 12:55:10 +00:00
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jsr print_cls
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2020-02-23 08:44:36 +00:00
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// print_euclid(128,2)
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2020-06-27 18:32:09 +00:00
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lda #<print_screen
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2019-08-07 19:00:19 +00:00
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sta.z print_line_cursor
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2020-06-27 18:32:09 +00:00
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lda #>print_screen
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2019-08-07 19:00:19 +00:00
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sta.z print_line_cursor+1
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2019-07-25 12:55:10 +00:00
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lda #2
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.b
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2020-06-27 18:32:09 +00:00
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lda #<print_screen
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2019-08-07 19:00:19 +00:00
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sta.z print_char_cursor
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2020-06-27 18:32:09 +00:00
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lda #>print_screen
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2019-08-07 19:00:19 +00:00
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sta.z print_char_cursor+1
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2019-07-25 12:55:10 +00:00
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lda #$80
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.a
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2019-07-25 12:55:10 +00:00
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jsr print_euclid
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2019-08-07 19:00:19 +00:00
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lda.z print_line_cursor
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sta.z print_char_cursor
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lda.z print_line_cursor+1
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sta.z print_char_cursor+1
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2020-02-23 08:44:36 +00:00
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// print_euclid(169,69)
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2019-07-25 12:55:10 +00:00
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lda #$45
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.b
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2019-07-25 12:55:10 +00:00
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lda #$a9
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.a
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2019-07-25 12:55:10 +00:00
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jsr print_euclid
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2019-08-07 19:00:19 +00:00
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lda.z print_line_cursor
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sta.z print_char_cursor
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lda.z print_line_cursor+1
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sta.z print_char_cursor+1
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2020-02-23 08:44:36 +00:00
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// print_euclid(155,55)
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2019-07-25 12:55:10 +00:00
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lda #$37
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.b
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2019-07-25 12:55:10 +00:00
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lda #$9b
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.a
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2019-07-25 12:55:10 +00:00
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jsr print_euclid
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2019-08-07 19:00:19 +00:00
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lda.z print_line_cursor
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sta.z print_char_cursor
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lda.z print_line_cursor+1
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sta.z print_char_cursor+1
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2020-02-23 08:44:36 +00:00
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// print_euclid(199,3)
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2019-07-25 12:55:10 +00:00
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lda #3
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.b
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2019-07-25 12:55:10 +00:00
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lda #$c7
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.a
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2019-07-25 12:55:10 +00:00
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jsr print_euclid
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2019-08-07 19:00:19 +00:00
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lda.z print_line_cursor
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sta.z print_char_cursor
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lda.z print_line_cursor+1
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sta.z print_char_cursor+1
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2020-02-23 08:44:36 +00:00
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// print_euclid(91,26)
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2019-07-25 12:55:10 +00:00
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lda #$1a
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.b
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2019-07-25 12:55:10 +00:00
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lda #$5b
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.a
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2019-07-25 12:55:10 +00:00
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jsr print_euclid
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2019-08-07 19:00:19 +00:00
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lda.z print_line_cursor
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sta.z print_char_cursor
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lda.z print_line_cursor+1
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sta.z print_char_cursor+1
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2020-02-23 08:44:36 +00:00
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// print_euclid(119,187)
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2019-07-25 12:55:10 +00:00
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lda #$bb
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.b
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2019-07-25 12:55:10 +00:00
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lda #$77
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2019-08-07 19:00:19 +00:00
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sta.z print_euclid.a
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2019-07-25 12:55:10 +00:00
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jsr print_euclid
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2020-02-23 08:44:36 +00:00
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// }
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2019-07-25 12:55:10 +00:00
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rts
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}
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2020-06-27 21:26:57 +00:00
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// Clear the screen. Also resets current line/char cursor.
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print_cls: {
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// memset(print_screen, ' ', 1000)
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jsr memset
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// }
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rts
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}
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2021-09-23 06:24:56 +00:00
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// void print_euclid(__zp(4) char a, __zp(7) char b)
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2019-07-25 12:55:10 +00:00
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print_euclid: {
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2021-09-23 06:24:56 +00:00
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.label b = 7
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.label a = 4
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2020-04-13 18:06:30 +00:00
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// print_uchar(a)
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2019-08-07 19:00:19 +00:00
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ldx.z a
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2020-04-13 18:06:30 +00:00
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jsr print_uchar
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2020-02-23 08:44:36 +00:00
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// print_char(' ')
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2019-07-25 12:55:10 +00:00
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lda #' '
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jsr print_char
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2020-04-13 18:06:30 +00:00
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// print_uchar(b)
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2019-08-07 19:00:19 +00:00
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ldx.z b
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2020-04-13 18:06:30 +00:00
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jsr print_uchar
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2020-02-23 08:44:36 +00:00
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// print_char(' ')
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2019-07-25 12:55:10 +00:00
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lda #' '
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jsr print_char
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2020-02-23 08:44:36 +00:00
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// euclid(a,b)
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2019-08-07 19:00:19 +00:00
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ldx.z b
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2019-07-25 12:55:10 +00:00
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jsr euclid
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2020-02-23 08:44:36 +00:00
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// euclid(a,b)
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2019-08-07 19:00:19 +00:00
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lda.z euclid.a
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2020-04-13 18:06:30 +00:00
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// print_uchar(euclid(a,b))
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2019-07-25 12:55:10 +00:00
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tax
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2020-04-13 18:06:30 +00:00
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jsr print_uchar
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2020-02-23 08:44:36 +00:00
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// print_ln()
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2019-07-25 12:55:10 +00:00
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jsr print_ln
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2020-02-23 08:44:36 +00:00
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// }
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2019-07-25 12:55:10 +00:00
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rts
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}
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2020-06-27 21:26:57 +00:00
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// Copies the character c (an unsigned char) to the first num characters of the object pointed to by the argument str.
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2021-08-10 15:48:55 +00:00
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// void * memset(void *str, char c, unsigned int num)
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2020-06-27 21:26:57 +00:00
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memset: {
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.const c = ' '
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.const num = $3e8
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.label str = print_screen
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.label end = str+num
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2021-09-23 06:24:56 +00:00
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.label dst = 2
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2020-06-27 21:26:57 +00:00
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lda #<str
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sta.z dst
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lda #>str
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sta.z dst+1
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2019-09-29 21:13:37 +00:00
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__b1:
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2020-06-27 21:26:57 +00:00
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// for(char* dst = str; dst!=end; dst++)
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lda.z dst+1
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cmp #>end
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bne __b2
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lda.z dst
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cmp #<end
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bne __b2
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2020-02-23 08:44:36 +00:00
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// }
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2019-07-25 12:55:10 +00:00
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rts
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2020-06-27 21:26:57 +00:00
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__b2:
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// *dst = c
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lda #c
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ldy #0
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sta (dst),y
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// for(char* dst = str; dst!=end; dst++)
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inc.z dst
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bne !+
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inc.z dst+1
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!:
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jmp __b1
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2019-07-25 12:55:10 +00:00
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}
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2020-04-13 18:00:13 +00:00
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// Print a char as HEX
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2021-08-10 15:48:55 +00:00
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// void print_uchar(__register(X) char b)
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2020-04-13 18:06:30 +00:00
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print_uchar: {
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2020-02-23 08:44:36 +00:00
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// b>>4
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2019-07-25 12:55:10 +00:00
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txa
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lsr
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lsr
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lsr
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lsr
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2020-02-23 08:44:36 +00:00
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// print_char(print_hextab[b>>4])
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2019-07-25 12:55:10 +00:00
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tay
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lda print_hextab,y
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2020-03-07 21:38:40 +00:00
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// Table of hexadecimal digits
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2019-07-25 12:55:10 +00:00
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jsr print_char
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2024-01-02 18:45:16 +00:00
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// b&0xf
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2019-07-25 12:55:10 +00:00
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lda #$f
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axs #0
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2024-01-02 18:45:16 +00:00
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// print_char(print_hextab[b&0xf])
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2019-07-25 12:55:10 +00:00
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lda print_hextab,x
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jsr print_char
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2020-02-23 08:44:36 +00:00
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// }
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2019-07-25 12:55:10 +00:00
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rts
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}
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// Print a single char
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2021-08-10 15:48:55 +00:00
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// void print_char(__register(A) char ch)
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2019-07-25 12:55:10 +00:00
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print_char: {
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2020-02-23 08:44:36 +00:00
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// *(print_char_cursor++) = ch
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2019-07-25 12:55:10 +00:00
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ldy #0
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sta (print_char_cursor),y
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2020-02-23 08:44:36 +00:00
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// *(print_char_cursor++) = ch;
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2019-08-07 19:00:19 +00:00
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inc.z print_char_cursor
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2019-07-25 12:55:10 +00:00
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bne !+
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2019-08-07 19:00:19 +00:00
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inc.z print_char_cursor+1
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2019-07-25 12:55:10 +00:00
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!:
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2020-02-23 08:44:36 +00:00
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// }
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2019-07-25 12:55:10 +00:00
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rts
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}
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2021-09-23 06:24:56 +00:00
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// __register(A) char euclid(__zp(4) char a, __register(X) char b)
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2019-07-25 12:55:10 +00:00
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euclid: {
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2021-09-23 06:24:56 +00:00
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.label a = 4
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2019-09-29 21:13:37 +00:00
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__b1:
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2020-02-23 08:44:36 +00:00
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// while (a!=b)
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2019-08-07 19:00:19 +00:00
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cpx.z a
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2019-09-29 21:13:37 +00:00
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bne __b2
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2020-02-23 08:44:36 +00:00
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// }
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2019-07-25 12:55:10 +00:00
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rts
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2019-09-29 21:13:37 +00:00
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__b2:
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2020-02-23 08:44:36 +00:00
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// if(a>b)
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2019-08-07 19:00:19 +00:00
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cpx.z a
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2019-09-29 21:13:37 +00:00
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bcc __b3
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2020-02-23 08:44:36 +00:00
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// b=b-a
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2019-07-25 12:55:10 +00:00
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txa
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sec
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2019-08-07 19:00:19 +00:00
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sbc.z a
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2019-07-25 12:55:10 +00:00
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tax
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2019-09-29 21:13:37 +00:00
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jmp __b1
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__b3:
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2020-02-23 08:44:36 +00:00
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// a=a-b
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2019-07-25 12:55:10 +00:00
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txa
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eor #$ff
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sec
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2019-08-07 19:00:19 +00:00
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adc.z a
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sta.z a
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2019-09-29 21:13:37 +00:00
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jmp __b1
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2019-07-25 12:55:10 +00:00
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}
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2020-06-27 21:26:57 +00:00
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// Print a newline
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print_ln: {
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2019-09-29 21:13:37 +00:00
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__b1:
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2024-01-02 18:45:16 +00:00
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// print_line_cursor + 0x28
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2020-06-27 21:26:57 +00:00
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lda #$28
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clc
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adc.z print_line_cursor
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sta.z print_line_cursor
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bcc !+
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inc.z print_line_cursor+1
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!:
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// while (print_line_cursor<print_char_cursor)
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lda.z print_line_cursor+1
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cmp.z print_char_cursor+1
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bcc __b1
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2019-07-25 12:55:10 +00:00
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bne !+
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2020-06-27 21:26:57 +00:00
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lda.z print_line_cursor
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cmp.z print_char_cursor
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bcc __b1
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2019-07-25 12:55:10 +00:00
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!:
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2020-06-27 21:26:57 +00:00
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// }
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rts
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2019-07-25 12:55:10 +00:00
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}
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2020-12-21 07:57:41 +00:00
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.segment Data
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2019-07-25 12:55:10 +00:00
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print_hextab: .text "0123456789abcdef"
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