mirror of https://github.com/hsoft/collapseos.git
16 lines
673 B
Plaintext
16 lines
673 B
Plaintext
This file describe tricks that are used throughout the code and might need
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explanation.
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or a: Equivalent to "cp 0", but results in a shorter opcode.
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xor a: sets A to 0 more efficiently than ld a, 0
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and 0xbf: Given a letter in the a-z range, changes it to its uppercase value
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if it's already uppercased, then it stays that way.
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Z if almost always used as a success indicator for routines. Set for success,
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Reset for failure. "xor a" (destroys A) and "cp a" (preserves A) are used to
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ensure Z is set. To ensure that it is reset, it's a bit more complicated and
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"unsetZ" routine exists for that, although that in certain circumstances,
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"inc a \ dec a" or "or a" can work.
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