Compiled Majiro scenario scripts (and other UI scripts like the console) use the .mjo extension. The extension most often seen for text source scripts is .mjs and .txt.

Type	Value	Description
char[16]	"MajiroObjV1.000" "MajiroObjX1.000"	File Signature V = decrypted X = encrypted
uint32	MainOffset	Bytecode offset to $main function
uint32	LineCount1	Number of lines in the script (equal to value of last line instruction)
uint32	FunctionCount	Number of functions in following table
Function[Count]	Functions	Function name hashes and their bytecode offsets
uint32	BytecodeSize	Size of following bytecode data.
byte[Size]	Bytecode	Bytecode instructions (encryption starts here)

[1] : LineCount is only non-zero when the #use_readflg on preprocessor is added to the script before compilation. Essentially only seen in story scripts.

Type	Value	Description
uint32	Hash	Hash of original function name
uint32	Offset	Bytecode offset to function start

See here for information on bytecode encryption.

The bytecode is a continuous set of instructions, each with variable length depending on the opcode.

Type	Value	Description
uint16	Opcode	Opcode ID that determines how the instruction is read and behaves
...	Operands	All remaining data depends on the opcode. An instruction can have 0 bytes of operands

WIP

Operand	Data	Description
Integer	int32
JumpOffset	int32
Hash	uint32
Placeholder	uint32	Placeholder for call address after first being run. Must be 0
Float	float32
VarOffset	int16
VarFlags	uint16	(bitmask)
ArgCount	uint16	Number of values on stack consumed by function call (first in, last out)
LineNumber	uint16	Line number from source script (1-indexed)
String	uint16 (N), char[N]	N includes the string null terminator. Majiro often treats N==0' as null` for this reason. But there's no evidence of this being supported in scripts.
TypeList	uint16 (N), byte[N]
CaseList	uint16 (N), int32[N]	List of switch case offsets, each absolute offset is calculated relative to the end of the respective offset element. i.e. case\[n\] += OperandOffset + 2 + (n+1) * 4

Opcode	Operands
ldc.i	Integer
ldc.r	Float
ldstr ctrl text	String
st. stp. stelem. stelemp. ld ldelem	VarFlags, Hash, VarOffset
call callp	Hash, Placeholder, ArgCount
syscall syscallp	Hash, ArgCount
line	LineNumber
argcheck alloca	TypeList
switch	CaseOffsets
br brfalse brtrue br.case bne.case blt.case ble.case bgt.case bge.case bsel.1 bsel.2 bsel.3 bsel.4 bsel.5 bsel.x	JumpOffset
add. sub. mul. div. rem shl shr ceq. cne. clt. cle. cgt. cge. and andl or orl xor neg. not notl nop.191 nop.1a8 nop.1a9 conv. ret pop proc bsel.clr bsel.jmp.4	(none)

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• Method: XOR cipher
• List of Majiro IL instructions
• Table of opcodes