Executable Format

Thru executable programs follow a specific binary format that includes a header, program bytecode, and trailer.

Program Structure

A Thru executable consists of three main components:

Component	Size	Description
Header	8 bytes	Version and metadata
Program	Variable	Executable bytecode
Trailer	8 bytes	Zero terminator

Header Format

The header is exactly 8 bytes long and contains version information.

Offset	Size	Field	Description
0	1	Version	Program format version (0x01)
1-7	7	Reserved	Reserved for future use

Version Field

Currently, only version 0x01 is supported.

01 00 00 00 00 00 00 00
^^ Version (0x01)
   ^^^^^^^^^^^^^^^ Reserved (7 bytes, typically zero)

Program Bytecode

The program bytecode section contains the executable instructions:

Starts immediately after the 8-byte header
Variable length depending on the program size
Contains the actual program instructions
Minimum size is 0 bytes (empty programs are valid)

Trailer Format

The trailer is exactly 8 bytes long and serves as a terminator.

Trailer Layout

Offset	Size	Field	Description
-8	8	Terminator	Must be zero (0x0000000000000000)

The last 8 bytes of the executable must be set to zero.

00 00 00 00 00 00 00 00
^^^^^^^^^^^^^^^^^^^^^^^ All bytes must be zero

Size Constraints

Total minimum size: 16 bytes (8-byte header + 8-byte trailer)
Header size: Exactly 8 bytes
Trailer size: Exactly 8 bytes
Program size: Variable (minimum 0 bytes)

Complete Example

Here’s a minimal valid Thru executable:

01 00 00 00 00 00 00 00   // Header: version 0x01 + 7 reserved bytes
95 00 00 00 00 00 00 00   // Program: 8 bytes of instructions
00 00 00 00 00 00 00 00   // Trailer: 8 zero bytes

In this example:

Total size: 24 bytes
Header size: 8 bytes
Program size: 8 bytes
Trailer size: 8 bytes