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27 lines
1.1 KiB
Plaintext
27 lines
1.1 KiB
Plaintext
This is a "Hello World" program for the Nintendo Entertainment System,
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which uses the sprite system to display and color-cycle the letters.
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Since NES cartridges tended to have sophisticated circuitry built into them
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that controlled memory addressing, several standards have arisen to represent
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this information. The program code for "Hello, NES" is split into two halves;
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a hello_prg.oph containing the executable code (PRG-ROM), and a hello_chr.oph
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containing the graphics tile information (CHR-ROM). These can then be packaged
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one of two ways - the popular iNES format (hello_ines.oph) or the
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mostly-defunct UNIF format (hello_unif.oph). Simply running
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ophis hello_ines.oph
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or
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ophis hello_unif.oph
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should produce hello.nes and hello.unf, respectively. Although UNIF is not a
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common format, its "chunk" system is not rare. The hello_unif.oph file
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demonstrates some techniques for automatically computing chunk sizes in Ophis.
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Be warned that as these techniques use the program counter, attempting to use
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labels to compute chunk size of assembled code is likely to backfire
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spectacularly - this technique should really only be used for inline strings
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and data.
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