17 lines
550 B
Plaintext
17 lines
550 B
Plaintext
;adding two 16-bit signed numbers, the first is stored at $10 and $11, the second at $12 and $13.
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;The result will be stored at $14 and $15.
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;add the low bytes
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LDA $10 ;low byte of first operand
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CLC
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ADC $12 ;low byte of second operand
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STA $14 ;low byte of sum
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;add the high bytes
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LDA $11 ;high byte of first operand
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ADC $13 ;high byte of second operand
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STA $15 ;high byte of result
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BVS HandleOverflow ;only check for overflow when adding the most significant bytes.
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