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71 lines
2.2 KiB
Markdown
71 lines
2.2 KiB
Markdown
[< back to index](../doc_index.md)
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### A note about Commodore 64
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#### Multifile programs
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A multifile program is a program stored on a disk that consists of the main program file that is executed first
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and several other files that can be loaded into memory on demand.
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This allows for creating programs that are larger than 64 kilobytes.
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Millfork allows building such programs, but leaves several things to the programmer:
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* tracking of which parts of the program are currently loaded and which are not
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* whether memory ranges of various parts overlap or not
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* whether loading succeeded or not
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##### Writing multifile programs
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You will need to create a platform definition file with multiple segments.
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The default segment should start at $80D.
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Example:
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segments=default,extra
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; the first file will contain the initial code:
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default_code_segment=default
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segment_default_start=$80D
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segment_default_codeend=$7fff
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segment_default_datastart=after_code
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segment_default_end=$7fff
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; the second file will contain the extra code:
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segment_extra_start=$8000
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segment_extra_codeend=$9fff
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segment_extra_datastart=after_code
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segment_extra_end=$cfff
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You also need to set `style=per_segment` in the `[output]` section.
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Annotate things you want to place in that file with the `segment` keyword:
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segment(extra)
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void extra_function () {
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//
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}
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Then in your code you need to load the file:
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load_file(last_used_device(), "eee"z)
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if errno == err_ok {
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extra_function()
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} else {
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// handle error
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}
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(Prefer `last_used_device()` instead of hardcoded `8`, so your program will work when loaded from any disk drive.)
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Compiling the program with `-o OUTPUT` will yield several PRG files.
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The default segment will be in `OUTPUT.prg`, the segment called `extra` in `OUTPUT.extra.prg` and so on.
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##### Packaging multifile programs
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The Millfork compiler does not create Commodore disk images.
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You can use a variety of tools to perform that task,
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for example the `c1541` tool shipped with [the VICE emulator](http://vice-emu.sourceforge.net/).
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To create a new disk image for the last example, use:
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c1541 -format "example,01" d64 example.d64 -write OUTPUT.prg start -write OUTPUT.extra.prg eee
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