DM1 File Formats

Dungeon Master File Formats

Dungeon Master PC 3.4 (DOS). All multi-byte values are little-endian (Watcom/Borland LSB-first bitfields).

DUNGEON.DAT — Dungeon Data

Field	Value
Size	~33 KB
Byte order	Little-endian
Dungeon ID	10 (DM)

Header (44 bytes)

Offset	Size	Field
0x00	2	Ornament random seed
0x02	2	Raw map data byte count
0x04	1	Map count
0x05	1	Reserved
0x06	2	Text data word count
0x08	2	Initial party location (packed: bits 11-10 = direction, 9-5 = Y, 4-0 = X)
0x0A	2	Square-first-thing count
0x0C	32	Thing counts (16 x uint16)

Map Descriptors (16 bytes each)

One descriptor per level, starting at offset 44:

Offset	Size	Field
0x00	2	Data offset
0x02	1	Width (stored as value-1)
0x03	1	Height (stored as value-1)
0x04	1	Floor ornament count
0x05	1	Wall ornament count
0x06	1	Difficulty
0x07	1	Creature type count
0x08	1	Door ornament count
0x09	1	Floor set selector
0x0A	1	Wall set selector
0x0B	1	Door set 0 selector
0x0C	1	Door set 1 selector
0x0D-0x0F	3	Reserved

Square Data (1 byte per cell)

Grid is stored column-major. Each byte encodes:

Bits	Field
7-5	Element type (0=wall, 1=corridor, 2=pit, 3=stairs, 4=door, 5=teleporter, 6=fake wall)
4	Has thing list
3-0	Element-specific data

Thing Encoding (uint16)

Bits  15-14  Direction (0-3)
Bits  13-10  Type (0-15)
Bits   9-0   Index

Special values: 0xFFFF = THING_NONE, 0xFFFE = THING_ENDOFLIST.

Thing Record Sizes

Type	Name	Size (bytes)
0	Door	4
1	Teleporter	6
2	Text string	4
3	Sensor	8
4	Group	16
5	Weapon	4
6	Armour	4
7	Scroll	4
8	Potion	4
9	Container	8
10	Junk	4
13	Projectile	8
14	Explosion	4

Compression

On-disc data may be FTL-compressed (signature: 0x8104). The loader requires decompressed data. FTL decompression uses a 20-byte frequency table prefix. File identity is verified by content hash, not filename.

GRAPHICS.DAT — Game Graphics

Field	Value
Size	~363 KB
Max bitmaps	600
Compression	12-bit LZW (GIF-style)

Bitmap Index

The file begins with a table of bitmap headers:

Field	Size	Description
Width	2	Bitmap width in pixels
Height	2	Bitmap height in pixels
Compressed size	4	LZW-compressed data size
Offset	4	File offset to compressed data

LZW Compression

Parameter	Value
Clear code	256
End-of-info code	257
First variable code	258
Max code	4,096
Code width	9-12 bits (grows dynamically)
Bit order	LSB-first

Pixel Format

• 4 bitplanes for 16-color indexed pixels
• Byte width per bitplane: (width + 7) / 8
• Palette: 6-bit RGB per channel (0-63, Atari ST/Amiga style)
• Framebuffer: 320x200 indexed

Save File Format

Field	Value
Magic	0x444D0001 ("DM\0\1")
Header size	512 bytes
Encryption key index	10

The save header is encrypted. The body contains FTL-compressed dungeon data (signature 0x8104) plus champion state, timers, and game info. A per-part byte checksum (F7059/F7060) validates integrity.

FTL Container Format (Amiga/X68000/SegaCD)

Field	Value
Magic	0x6160
Common header	20 bytes

Offset  Size  Description
0x00    2     Magic: 0x6160
0x02    2     Checksum
0x04    14    Reserved
0x12    2     Hunk count

Each hunk header is 12 bytes:

Offset	Size	Field
0x00	2	Type (0x0010=BSS, 0x0011=DATA, 0x0012=CODE)
0x02	2	Unknown
0x04	4	Offset
0x08	4	Size