INT File Format

Format files in INT- Fallout

The paper describes the format of INT Files for Fallout and Fallout2. Information about this was obtained by analyzing source compiler scripts for Fallout2. Baseline compiler texts were obtained from the source compiler scripts for the game Klingon Academy. Compilers for the two games overlap by about 80%.

Background

INT files are compiled scripts, designed for animating the world of Fallout. They set the behavior of all objects on the maps, and are used to create dialogues with the characters in the game.

File Format

INT files consists of the following parts:

• Script initialization code
• A table of procedure descriptions
• A list of the names of procedures and variables
• A list of text strings
• Script object initialization code
• The body of procedures

Note: All numbers are stored in big-endian format (the most significant byte first).

Script Initialization Code

Script initialization code is for the transfer of control to script object initialization code and providing the correct procedure return addresses(?).

This part of an INT file should have a fixed size of 42 bytes, because that is the offset at which it looks for the table of procedures.

Table 2.1 - script initialization code

Offset	Size	Value		Description
0x0000	2 bytes	0x8002	O_CRITICAL_START	Start of 'Critical' code section. (see 'script object initialization code')
0x0002	2 bytes	0xC001	O_INTOP	Return address of 'start' procedure
0x0004	4 bytes	0x00000012	INT (0x00000012)
0x0008	2 bytes	0x800D	O_D_TO_A	Entry return address of the 'start' procedure in the stack addresses
0x000A	2 bytes	0xC001	O_INTOP	Starting address of script object initialization code
0x000C	4 bytes	...
0x0010	2 bytes	0x8004	O_JMP	Jump to script object initialization code
0x0012	2 bytes	0x8010	O_EXIT_PROG	The specific function of each opcode is not entirely clear. Apparently they support the correct completion of initialization scripts.
0x0014	2 bytes	0x801A	O_POP
0x0016	2 bytes	0x8020	O_POP_FLAGS_RETURN
0x0018	2 bytes	0x801A	O_POP
0x001A	2 bytes	0x8021	O_POP_FLAGS_EXIT
0x001C	2 bytes	0x801A	O_POP
0x001E	2 bytes	0x8022	O_POP_FLAGS_RETURN_EXTERN
0x0020	2 bytes	0x801A	O_POP
0x0022	2 bytes	0x8023	O_POP_FLAGS_EXIT_EXTERN
0x0024	2 bytes	0x8024	O_POP_FLAGS_RETURN_VAL_EXTERN
0x0026	2 bytes	0x8025	O_POP_FLAGS_RETURN_VAL_EXIT
0x0028	2 bytes	0x8026	O_POP_FLAGS_RETURN_VAL_EXIT_EXTERN

Table of procedures

The table of procedures contains information about all the available procedures in an INT file.

It should be noted that the first procedure in INT files is a procedure named '..............' (14 periods). This procedure does not have a body, and is designed to make indices of procedures start at 1, not 0.

Table 2.2-Table of procedures

Offset	Size	Description
0x0000	4 bytes		The number of procedures in the table
0x0004	4 bytes	Entry0	Name procedure (offset in the list of names).
0x0008	4 bytes		Set flags according to the type of procedure. P_TIMED = 0x01 - Timed (delayed?) procedure P_CONDITIONAL = 0x02 - Conditional procedure P_IMPORT = 0x04 - Imported procedure P_EXPORT = 0x08 - Exported procedure P_CRITICAL = 0x10 - Critical procedure Note: Creating timed and conditional procedures is not entirely understood. It is also not clear if they are used at all in Fallout. Because of a bug in the original BIS compiler cannot compile conditional procedures.
0x000C	4 bytes		The delay in milliseconds for timed procedures
0x0010	4 bytes		The position in the file code expressing conditions for conditional procedures (the offset from the beginning of the file).
0x0014	4 bytes		The position in the file of the function body (offset from the beginning of the file).
0x0018	4 bytes		The number of arguments of the procedure
...	...	...	...
Note: The offset in the table given from the beginning of the table of procedures, not the start of the file.

List of procedure and variable names

This part of the INT file contains the names of script variables and procedures. It does not include the names of local variables declared within procedures.

Some information in this section may be redundant, since referring to global variables is done by index, not by name.

Table 2.3. List of names of procedures and variables

Offset	Size	Value	Description
0x0000	4 bytes	totalSize	Size of the list of names, except the ending, in bytes.
0x0004	2 bytes	length0	The length of name 0, including the null (zero) terminator, in bytes. Note: Length 'object name' MUST be EVEN. Otherwise, the INT file becomes unexecutable.
0x0006	length0 bytes		'Name 0' A string of ASCII characters ending with a null (zero) byte. Another null will be added if necessary to make the total length of the string even.
...	...	...	...
totalSize	4 bytes	0xFFFFFFFF	Indicates the end of the list.
Note: The offset in the table are given from the beginning of the list of names, not the start of the file. The addresses of names/strings are specified using offsets from the beginning of the list and point to the first character of the string, not its length.

List of strings

This part of the INT file contains all the string constants used in the script. The format is the same as the list of procedure and variables. It is possible for this section to be empty (i.e. no strings are used).

Script object initialization code

This part of the script is to initialize global script variables, export and initialize variables, export procedures, and moving to the 'start' procedure (or returning to the script initialization code if there isn't one).

Table 2.5. Script object initialization code

Offset	Size	Value		Description
0x0000	2 bytes	0x802C	O_SET_GLOBAL		The specific meaning of this opcode is not entirely clear. Possibly for switching to the global script stack.
0x0002	2 bytes	0x9001 0xA001 0xC001	O_STRINGOP O_FLOATOP O_INTOP	Variable Type	Global variable 0
0x0004	4 bytes	value0		Value of variable
...	...	...	...	...	...
	2 bytes	0x9001	O_STRINGOP	Variable name	Exports variable named name0
	4 bytes	name0
	2 bytes	0x8016	O_EXPORT_VAR	Exports variable
...	...	...	...	...	...
	2 bytes	0x9001 0xA001 0xC001	O_STRINGOP O_FLOATOP O_INTOP	Type of assigned value	Assigns the value value0 to the external variable name0
	4 bytes	value0		Value
	2 bytes	0x9001	O_STRINGOP	Variable name
	4 bytes	name0
	2 bytes	0x8015	O_STORE_EXTERNAL	Assign to external variable
...	...	...	...	...	...
	2 bytes	0xC001	O_INTOP	The number of arguments for the procedure	Export the procedure 'name_p'
	4 bytes	numArgs
	2 bytes	0x9001	O_STRINGOP	Procedure name
	4 bytes	name_p
	2 bytes	0x8017	O_EXPORT_PROC	Export procedure
...	...	...	...	...	...
	2 bytes	0xC001	O_INTOP	Variable name	The number of arguments for the 'start' procedure.
	4 bytes	0	INT (0)
	2 bytes	0x8003	O_CRITICAL_DONE	End of 'Critical' code section (see 'script initialization code').
	2 bytes	0xC001	O_INTOP	Address transition	The transition to the procedure 'start', and or return to the script initialization code if there isn't one
	4 bytes	address off the 'start' procedure or 0x00000012
	2 bytes	0x8004	O_JMP	The jump to the 'start' procedure or return to script initialization code

Body of procedure code

This part of the INT file contains a sequence of opcodes implementing the procedures of the script.

Discussion of the meaning of opcodes and their arguments is beyond the scope of this paper.

Original file taken from TeamX documentation