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Add documentation for the MONOTONE song file format (.mon files)
Co-authored-by: cs127 <[email protected]>
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‎main.bas

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print "Hello, World!"

‎main.exe

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‎monotone.txt

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╒════════════════╕
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│ FILE STRUCTURE │
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╞════════╤═══════╧══════╤══════════════════════════════════════════════════════╕
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│ OFFSET │ TYPE │ CONTENT │
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╞════════╪══════════════╪══════════════════════════════════════════════════════╡
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│ $0000 │ uint8_t │ Length of magic bytes (always 8) │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $0001 │ char[8] │ Magic bytes: "MONOTONE" │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $0009 │ uint8_t │ Length of song title (max 40) │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $000A │ char[40] │ Song title │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $0032 │ uint8_t │ Length of song comment (max 40) │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $0033 │ char[40] │ Song comment │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $005B │ uint8_t │ Song format version (currently always 1) │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $005C │ uint8_t │ Number of patterns │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $005D │ uint8_t │ Number of channels │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $005E │ uint8_t │ Size of each cell (note + effect) (always 2) │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $005F │ uint8_t[256] │ Order list (end of song / empty orders = $FF) │
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├────────┼──────────────┼──────────────────────────────────────────────────────┤
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│ $015F │ uint16_t[] │ Cells / pattern data (documented below) │
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└────────┴──────────────┴──────────────────────────────────────────────────────┘
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╒════════════════════════╕
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│ PATTERN/CELL STRUCTURE │
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├────────────────────────┴─────────────────────────────────────────────────────┐
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│ The data structure at $015F is an array of all the patterns │
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│ (the number of patterns is stored at $005C). │
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│ │
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│ Each pattern is an array of its rows (every pattern has 64 rows). │
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│ │
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│ Each row is an array of its cells (note + effect) │
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│ (the number of cells per row is the number of channels, stored at $005D). │
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│ │
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│ Each cell is a 16-bit integer, structured as follows: │
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│ │
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│ HIGH BYTE LOW BYTE │
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│ ──────── ──────── │
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│ nnnnnnne eepppppp │
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│ ││││││││ ││││││││ │
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│ ││││││││ ││└┴┴┴┴┴─ parameter of effect (see below for more explanation) │
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│ │││││││└────┴┴─────── effect type (0-7) (5,6,7 map to B,D,F respectively) │
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│ └┴┴┴┴┴┴────────────── note (0-127) (0=empty, 1-126=A0-D11, 127=off) │
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│ │
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│ For single-parameter effects (1xx, 2xx, 3xx, Bxx, Dxx, and Fxx), │
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│ all six parameter bits are used to encode xx, ranging from $00 to $3F. │
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│ │
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│ For double-parameter effects (0xy and 4xy), │
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│ the upper three and lower three parameter bits are used to encode │
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│ x and y respectively, each ranging from $0 to $7. │
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│ │
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│ Note that Intel's architecture is little-endian, meaning that each cell's │
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│ low byte is written before its high byte. │
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│ │
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│ The size of the data structure stored at $015F is 128*C*P bytes, where │
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│ C is the number of channels, and │
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│ P is the number of patterns. │
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│ │
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│ (2 bytes per cell * C cells per row * 64 rows per pattern * P patterns) │
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└──────────────────────────────────────────────────────────────────────────────┘

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