fun/web/documentation/bytecode-format/bytecode-format.md

layout	published	noToc	noComments	noDate	title	subtitle	description	permalink	lang	tags
page	true	false	false	false	Bytecode Format (Overview)	Reference for the bytecode format (split out from internals for convenience).	Reference for the bytecode format (split out from internals for convenience).	/documentation/bytecode-format/	en	bytecode convenience format internals out reference split

This document summarizes the Fun bytecode format. For deep VM details, see internals.

Goals

• Compact representation for fast loading and dispatch
• Stable header with room for versioning

File layout (typical)

1. Header
   • Magic number / signature
   • Format version
   • Flags (endianness, feature bits)
   • Offsets to sections
2. Constants table
   • Literals: numbers, strings, compound constants
3. Code section
   • Functions/procedures with instruction streams
   • Line/column mapping (optional for debugging)
4. Auxiliary tables
   • Imports/exports, names, debug info (optional)

Instructions

• Fixed-size or small-variant opcodes grouped by domain (math, logic, stack, call, control flow, etc.).
• Operands encoded inline following the opcode (width varies by instruction).

Versioning and compatibility

• The header's version field allows the VM to refuse or translate older/newer formats.
• Keep additions backward-compatible when possible by appending sections or flags.