SCUMM v5 — Resource File (MONKEY.001)

The resource file (MONKEY.001 for MI1, MONKEY2.001 for MI2) holds the game's bulk data: every room, global script, sound, costume, and charset. It is one big tree of tagged blocks under a single LECF container. The .000 index file and the LOFF table at the top of this file are what turn a resource id into a byte position inside it.

At a glance

MONKEY.001
└─ LECF                    LucasArts container — the whole file
   ├─ LOFF                 room id → ROOM offset  (see Index File)
   └─ LFLF × N             one bundle per room
      ├─ ROOM              the room itself  (see ROOM Block)
      │  ├─ RMHD           width, height, object count
      │  ├─ CLUT           256-entry room palette
      │  ├─ TRNS           transparent palette index
      │  ├─ EPAL           legacy EGA palette (unused on VGA)
      │  ├─ CYCL           colour-cycling effects
      │  ├─ SCAL           perspective actor scaling
      │  ├─ BOXD           walk boxes  (see Walk Boxes)
      │  ├─ BOXM           walk-box adjacency matrix
      │  ├─ RMIM           background image container
      │  │  ├─ RMIH        image header — z-plane count
      │  │  └─ IMxx        one image frame
      │  │     ├─ SMAP     background bitmap (strips)
      │  │     └─ ZPxx     z-plane masks
      │  ├─ OBIM × M       object image
      │  │  ├─ IMHD        object image header
      │  │  └─ IMxx        per-state image frames
      │  ├─ OBCD × M       object code + name
      │  │  ├─ CDHD        object code header
      │  │  ├─ VERB        verb → script handlers
      │  │  └─ OBNA        object display name
      │  ├─ ENCD           entry script
      │  ├─ EXCD           exit script
      │  ├─ NLSC           local-script count
      │  └─ LSCR × K       room-local scripts
      ├─ SCRP              global script
      ├─ SOUN              sound resource
      ├─ COST              costume (actor animation)
      └─ CHAR              character set / font

Every node is a block: a 4-character ASCII tag, then a u32 big-endian size, then the payload. The size includes the 8-byte header, so a block runs from its tag to start + size. Container blocks (LECF, LFLF, ROOM, RMIM, OBIM, OBCD, IMxx) hold other blocks as their payload; the rest are leaves carrying data. The .000 index never stores an absolute position into this file — LOFF does.

Sources

• ScummVM Technical Reference — block / resource layout, at https://wiki.scummvm.org/index.php?title=SCUMM/Technical_Reference. Block roles are summarized in our own words and confirmed empirically against MI1; the LOFF-points-at-ROOM detail below was derived against MI1 (see the index file doc).

⚠️ Block sizes are big-endian; payload fields are little-endian. The u32 size after each tag reads big-endian and counts the 8-byte header, but the integers inside a payload (counts, offsets, coordinates) are little-endian. Mixing the two is the classic first-parse bug.

1. The container layers — LECF, LOFF, LFLF

LECF is the single top-level block: the entire .001 file is its payload. Its first child is LOFF, a table mapping each room id to the absolute byte offset of that room's ROOM block — not the enclosing LFLF wrapper (the distinction matters when resolving resources; the byte layout and the reasoning live in the index file doc, §5).

After LOFF come the LFLF blocks, one per room. An LFLF is a "disk" bundle: it carries that room's ROOM block plus any global scripts, sounds, costumes, and charsets that ship alongside it. A resource directory in the .000 index names the owning room of each global resource, and the resource physically lives inside that room's LFLF — so a single LFLF (in MI1, room 10's) holds the bulk of the game's global scripts.

2. Inside a ROOM

A ROOM block bundles everything about one room — geometry, palette, background, walkable floor, objects, and scripts — in a canonical child order. The blocks below are catalogued here as a map of the file; each has its own deep-dive doc.

Background image (RMIM). RMIM is a container for the room's background and its z-plane masks: RMIH (a header whose key field is the number of z-planes that follow), then one IMxx frame holding the SMAP bitmap and any ZPxx masks. SMAP stores the picture as 8-pixel-wide vertical strips, each compressed independently; each ZPxx is a per-strip mask of the pixels actors should be drawn behind. See Background Bitmaps and Z-Plane Masks.

Objects (OBIM + OBCD). Each room object has two blocks. OBIM is its visual — an IMHD (position, dimensions, number of states) plus one or more IMxx frames (e.g. a chest's closed/open states). OBCD is its interactive side — a CDHD (id, position, dimensions, parent object), a VERB (verb-id → bytecode handlers for Look At / Pick Up / Use), and OBNA (the display name shown on hover). See Room Objects.

Room scripts. ENCD and EXCD are the bytecode that runs as the player enters and leaves the room. NLSC gives the count of room-local scripts, each of which follows as an LSCR block (id + bytecode body). The bytecode itself is the opcode reference's subject.

3. Per-LFLF global leaves

Alongside the ROOM, an LFLF may carry global resources that the .000 directories assign to this room:

4. Pitfalls cheat-sheet