Behavior

The BEHAVIOR lump is part of the Hexen map format, and stores the of compiled ACS scripts, which are output created by the ACC  tool. Given the difference in records size between the Doom and Hexen format for THINGS and LINEDEFS lump, the presence or absence of a BEHAVIOR lump also serves to identify the format of the entire map in ports which support several different formats.

Lump structure
The BEHAVIOR lump contains compiled ACS scripts for the map. There exist three different formats for BEHAVIOR lumps, the original Hexen one is identified by a four-byte header of ACS\0 (0x41435300); ZDoom also uses two different "enhanced" formats identified by ACSE (0x41435345) and ACSe (0x41435365).

Behavior lumps are compiled with ACC. The version of ACC maintained by Marisa Heit (Randi) needs the -h command line parameter to produce ACS\0 bytecode, since many of the ACS functions it supports are only available in the ZDoom formats.

The Eternity Engine's ACS VM can now interpret all three bytecode formats.