34 lines
1.6 KiB
Markdown
34 lines
1.6 KiB
Markdown
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# Bytecode
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These files are [instructions][instructions] in their binary form along with their arguments. These files also contain a header.
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These files are meant to be executed by the [interpreter][interpreter].
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## The header
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The header contains a magic number, which is hex `12345678`, a version number, an optional hash of the associated [assembler file][asm_file], the entry point of the program and the MMU mappings required by the program.
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## Binary instructions
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Instructions fall in two categories: normal and extended.
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Instructions are variable-length instructions, and their size is anywhere between one and four bytes.
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### First byte
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The first byte denotes the instruction type.
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The most significant two bits represent the argument scheme:
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`00`: No arguments, the instruction ends there
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`01`: One argument from a register
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`10`: Two arguments from registers
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`11`: An immediate argument
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The least significant six bits of the first byte represent the opcode. If it is bin `111111` then the instruction is extended and its opcode is stored in the second byte.
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### The arguments
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In the case of one or two arguments from registers, the opcode is followed by one or two bytes containing the number of the register from hex `00` to hex `ff`.
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In the case of an immediate argument, it is encoded as either a big-endian 16-bit integral number or a decimal value in the following format:
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MSB: sign of the number, `1` means negative
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Subsequent 11 bits: mantissa
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Remaining 4 bits: exponent, the power of two the mantissa is taken to
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[instructions]: ./instructions.md
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[interpreter]: ./interpreter.md
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[asm_file]: ./asm_file.md
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