mirror of
https://github.com/Michaelangel007/apple2_russian_peasant_multiplication.git
synced 2024-12-21 14:30:06 +00:00
347 lines
7.5 KiB
ArmAsm
347 lines
7.5 KiB
ArmAsm
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; ASC
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; DFB
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;.include "ca65_fixes.inc"
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ZERO_LEAD EQU $00
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KEY_CR EQU $8D
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KEY_ESC EQU $9B
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KEY_0 EQU $B0 ; '0' = $30
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KEY_9 EQU $B9 ; '9' = $39
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pDigits EQU $FA
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Carry EQU $FC
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Div EQU $FD
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KEYBOARD EQU $C000
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KEYSTROBE EQU $C010
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TEXT EQU $FB2F ; Init text mode and window
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HOME EQU $FC58
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RDKEY EQU $FD0C
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COUT EQU $FDED
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__main = $2000
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; Header for DOS 3.3 binary file; remove 2 lines for ProDOS
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DW __main
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DW __end - __main
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; main()
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ORG __main
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LDA #7 ; Version
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JSR TEXT ; Just in case we are in graphics mode
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JSR HOME
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JSR InitABS ; Init A,B,S
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JSR IntroH
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JSR InputA ; Input
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JSR InputB
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JSR IntroS
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MulDigit ; Calc
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JSR IsZeroB
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BCS OutS
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JSR IsOddB
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BCC EvenS
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JSR AddAToS
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EvenS
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JSR ShlA
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JSR ShrB
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CLC
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BCC MulDigit ; ^ (always)
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OutS
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JSR PrintS ; output
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;RTS ; NOTE: DOS3.3 BRUN bug doesn't exit, should JMP $3D0
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JMP $0000
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InputA
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JSR IntroA
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JSR GetPtrA
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BNE GetString
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InputB
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JSR IntroB
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JSR GetPtrB
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; intentional fall int GetString
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GetString ; common entry point
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STX pDigits
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STY pDigits+1
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LDX #0 ; digits length
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_linechar
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JSR GetDigit ; C=1 enter, C=0 digit
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BCS _linedone
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JSR COUT ; preserves A,Y
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AND #$F ; C=0 digit
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STA Buffer,X
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INX
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BPL _linechar ; or BNE for 255 digits
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BMI IntroE ; error if > 127 digits
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_linedone ; Now move digits from $200 -> DigitsA, DigitsB, etc.
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LDY #0 ; X = src, Y = dst offset
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CPX #0 ; any digits?
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BEQ _movedone ; No digits!
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_moveline
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DEX
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LDA Buffer,X
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STA (pDigits),Y ; digit[y] = char & 0xF
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INY
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CPX #0
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BNE _moveline ; ^ max 256 digits
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_movedone
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BEQ PrintCR ; v (always)
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GetDigit
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; LDA KEYBOARD
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; BPL GetDigit
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; STA KEYSTROBE
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JSR RDKEY
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CMP #KEY_CR
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BEQ _eol
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CMP #KEY_ESC
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BEQ _esc
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CMP #KEY_0
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BCC GetDigit
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CMP #KEY_9+1
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BCS GetDigit
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RTS
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_eol SEC ; C=1 enter
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RTS
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_esc ; Unwind stack of InputA/B
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PLA
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PLA
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RTS ; Return to who originally called main()
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GetPtrA
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LDX #<DigitsA ; lo byte
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LDY #>DigitsA ; hi byte
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RTS
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GetPtrB
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LDX #<DigitsB
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LDY #>DigitsB
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RTS
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GetPtrS
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LDX #<DigitsS
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LDY #>DigitsS
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RTS
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InitABS
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LDA #$00
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TAX
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_zero
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STA DigitsA,X
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STA DigitsB,X
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STA DigitsS,X
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INX
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BNE _zero ; zero digits[0..$FF]
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RTS
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IntroA LDY #OffsetA
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BNE _intro
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IntroB LDY #OffsetB
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BNE _intro
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IntroS LDY #OffsetS
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BNE _intro
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IntroE LDY #OffsetE
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BNE _intro
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IntroH
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LDY #OffsetH
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_intro
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LDA _text,Y
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BEQ _outro ; asciiz
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JSR COUT
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INY
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BNE _intro
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_outro
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RTS
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PrintCR
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LDA #KEY_CR
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JMP COUT
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; ________________________________________________________________________
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; Pseudo BCD - one byte per digit
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; ________________________________________________________________________
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; ========================================
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PrintA
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JSR GetPtrA
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BNE _print
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PrintB
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JSR GetPtrB
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BNE _print
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PrintS
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JSR GetPtrS
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_print
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STX _bcd+1
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STY _bcd+2
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LDX #ZERO_LEAD ; Default to leading zero ($0)
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LDY #$FF ; start at digits[255]
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_bcd
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LDA $FFFF,Y ; NOTE: Self-Modified by _print
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BNE _digit ; digits[i] == 0 && leadingzero
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CPX #ZERO_LEAD ; X != 0
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BEQ _skip
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_digit
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CLC
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ADC #KEY_0 ; 0 -> $B0 .. 9 -> $B9
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TAX ; If digit printed stop checking for leading zero
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JSR COUT
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_skip
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DEY ;
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CPY #$FF ; digits[255] ?
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BNE _bcd ; ^
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; Bug fix: If no digits were printed then number must be zero
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LDA #0 ; print '0'
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TAY ; no length
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CPX #ZERO_LEAD
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BEQ _digit
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BNE PrintCR ; ^ (always) move to next line when done
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; ========================================
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AddAToS
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LDY #0
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CLC
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_add
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LDA DigitsS,Y
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ADC DigitsA,Y
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CMP #$A ; Base=10, C = (a+s+carry) >= 10
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BCC _overflow
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SBC #$A ; C=1, A = A - 9 - C
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_overflow
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STA DigitsS,Y
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INY
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BNE _add
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RTS
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; ========================================
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IsOddB
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LDY #0
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LDA DigitsB,Y
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AND #1
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BEQ _not_zero ; Even -> C=0
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BNE _is_zero ; Odd _> C=1
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; ========================================
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IsZeroB
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LDY #0
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_is_0
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LDA DigitsB,Y
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BNE _not_zero
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INY
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BNE _is_0
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_is_zero
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SEC
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RTS
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_not_zero
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CLC
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RTS
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; ========================================
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ShlA
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LDY #0
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CLC
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_shl
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LDA DigitsA,Y
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TAX
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LDA Mul2Digit,X
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ADC #0
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STA DigitsA,Y
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LDA Mul2Carry,X
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ROR
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INY
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BNE _shl
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RTS
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; ========================================
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ShrB
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LDY #$FF ; start at digits[255]
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LDX #0 ; digits processed
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STX Carry ; $00 .. 9*2 = $18
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_shr
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CLC ;
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LDA DigitsB,Y ; sum = digit[i] + carry
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ADC Carry ; A=0000_00xy C=0/1
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ROR ; A=c000_000x, C=y
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AND #$F ; A=0000_000x
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STA DigitsB,Y ; digit[i] = (sum / 2)
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LDA #0 ;
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BCC _shr_next ; C=0 -> Carry = 0
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LDA #10 ; C=1 -> Carry = 10 (base)
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_shr_next
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STA Carry ; carry = (sum & 1) ? BASE : 0
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DEY
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INX ; we need to compare y=$FF without disturbing carry
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BNE _shr ; max 256 digits -- solution, use X reg :-)
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RTS
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Mul2Digit ; Digit
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DFB 0 ; 0*2 = 0 0
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DFB 2 ; 1*2 = 0 2
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DFB 4 ; 2*2 = 0 4
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DFB 6 ; 3*2 = 0 6
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DFB 8 ; 4*2 = 0 8
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DFB 0 ; 5*2 = 1 0
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DFB 2 ; 6*2 = 1 2
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DFB 4 ; 7*2 = 1 4
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DFB 6 ; 8*2 = 1 6
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DFB 8 ; 9*2 = 1 8
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Mul2Carry ; Carry
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DFB 0 ; 0*2 = 0 0
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DFB 0 ; 1*2 = 0 2
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DFB 0 ; 2*2 = 0 4
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DFB 0 ; 3*2 = 0 6
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DFB 0 ; 4*2 = 0 8
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DFB 1 ; 5*2 = 1 0
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DFB 1 ; 6*2 = 1 2
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DFB 1 ; 7*2 = 1 4
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DFB 1 ; 8*2 = 1 6
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DFB 1 ; 9*2 = 1 8
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_text
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TextH ; Header
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ASC "RUSSIAN PEASANT MULTIPLICATION"
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DFB KEY_CR
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DFB KEY_CR
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DFB 0
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TextA
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ASC "INPUT A"
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DFB KEY_CR
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ASC "?"
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DFB 0
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TextB
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ASC "INPUT B"
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DFB KEY_CR
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ASC "?"
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DFB 0
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TextE
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DFB KEY_CR
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ASC "WARNING"
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ASC ": MORE THAN 127 CHARS"
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DFB KEY_CR
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DFB 0
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TextS
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ASC "= "
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DFB 0
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OffsetH EQU TextH - _text
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OffsetA EQU TextA - _text
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OffsetB EQU TextB - _text
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OffsetE EQU TextE - _text
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OffsetS EQU TextS - _text
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__end
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; Pad until end of page, these globals are not stored on disk
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DUM *
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DS \
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DigitsA DS 256 ; stupid assembler can't use variable 'a'
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DigitsB DS 256
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DigitsS DS 256
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Buffer DS 256
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DEND
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