49 lines
856 B
Text
49 lines
856 B
Text
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Arithmetic: PHA ;push accumulator and X register onto stack
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TXA
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PHA
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JSR GetUserInput ;routine not implemented
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;two integers now in memory locations A and B
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;addition
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LDA A
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CLC
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ADC B
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JSR DisplayAddition ;routine not implemented
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;subtraction
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LDA A
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SEC
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SBC B
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JSR DisplaySubtraction ;routine not implemented
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;multiplication - overflow not handled
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LDA A
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LDX B
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Multiply: CLC
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ADC A
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DEX
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BNE Multiply
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JSR DisplayMultiply ;routine not implemented
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;division - rounds up
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LDA A
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LDX #0
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SEC
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Divide: INX
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SBC B
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BCS Divide
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TXA ;get result into accumulator
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JSR DisplayDivide ;routine not implemented
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;modulus
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LDA A
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SEC
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Modulus: SBC B
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BCS Modulus
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ADC B
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JSR DisplayModulus ;routine not implemented
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PLA ;restore accumulator and X register from stack
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TAX
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PLA
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RTS ;return from subroutine
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