SCUMM/V6 opcodes
Currently all entries from the reference on the main ScummVM website have been transferred - please proofread and fix formatting where applicable.
SCUMM V6 opcodes
The following conventions are used in the encoding descriptions.
| $AB | The constant hexadecimal byte 0xAB. |
| value[8] | A constant byte value. |
| value[16] | A constant word LE value. |
The following conventions are used in the stack descriptions:
(in1, in2, in3 : out1, out2)
Indicates that the opcode is called with three items on the stack (the most recently pushed being in3) and replaces them with two items on the stack (the most recently pushed being out2).
abs ($C4)
Stack
(in : out)
Operation
out := abs(in)
The absolute value of the top-most item on the stack is calculated. (The absolute value being the value with the sign bit stripped off.)
actorFollowCamera ($79)
actorSet ($9D)
add ($14)
Stack
(in1, in2 : out)
Operation
out := in1 + in2
Performs a division operation on the stack.
animateActor ($82)
arrayOps (This instruction varies considerably according to the form.)
Encoding
load array:
A4 CD arrayp16
define array:
A4 D0 arrayp16 data...
set array:
A4 D4 arrayp16
Stack
...todo...
6.4.7 MM 95 beginOverride
MM 6C breakHere
MM CA breakMaybe
MM 5A byteArrayDec
MM 52 byteArrayInc
byteArrayIndexedRead
Encoding
0A arrayp8
Stack
( indexx , indexy : value )
Operation
value := arrayp [ indexx , indexy ]
Reads the value at offset ( indexx , indexy ) from the array whose resource number is pointed to by arrayp . The array can be a byte or word array; byte values are not sign extended. Note that because arrayp is encoded as a byte, it can only point to a word variable in the range 0000 to 00FF. Use wordArrayIndexedRead for a more general form.
byteArrayIndexedWrite
Encoding
4A arrayp8
Stack ( indexx , indexy , value : -)
Operation arrayp [ indexx , indexy ] := value
Writes value to the array whose resource number is pointed to by arrayp at offset ( indexx , indexy ). The array can be a byte or word array; byte when writing to a byte array, value is truncated. Note that because arrayp is encoded as a byte, it can only point to a word variable in the range 0000 to 00FF. Use wordArrayIndexedWrite for a more general form.
byteArrayRead
Encoding
06 arrayp8
Stack
( index : value )
Operation
value := arrayp [0, index ]
Reads the value at position (0, index ) from the array whose resource number is pointed to by arrayp . The array can be a byte or word array; when writing to an array, byte values are not sign extended. Note that because arrayp is encoded as a byte, it can only point to a word variable in the range 0000 to 00FF. Use wordArrayRead for a more general form.
byteArrayWrite
Encoding
46 arrayp8
Stack
( index value : -)
Operation
arrayp [0, index ] := value
Writes value to the array whose resource number is pointed to by arrayp at offset (0, index ). The array can be a byte or word array; when writing to a byte array, value is truncated. Note that because arrayp is encoded as a byte, it can only point to a word variable in the range 0000 to 00FF. Use wordArrayWrite for a more general form.
MM 56 byteVarDec
MM 4E byteVarInc
MM 9A createBoxMatrix
MM 6B cursorCommand
MM 68 cutScene
delay
Encoding
B0
Stack
( delay : -)
Operation
Prevents the current thread from being rescheduled until delay ticks have passed. Deschedules immediately.
delayLonger
Encoding
B1
Stack
( delay : -)
Operation
Prevents the current thread from being rescheduled until delay× 60 ticks have passed ( delay seconds). Deschedules immediately.
delayVeryLong
Encoding
B2
Stack
( delay : -)
Operation
Prevents the current thread from being rescheduled until delay× 3600 ticks have passed ( delay minutes). Deschedules immediately.
dim
Encoding BC type8 arrayp16
Stack ( max : -)
Operation
Allocates or frees an array.
If type is CC, then the array whose resource number is pointed to by arrayp is freed. Otherwise, a new one-dimensional array with a maximum index of max (i.e., max is one less than the size) is allocated and the resource number written to arrayp .
When allocating an array, if type is C7 then the array will contain words; if it is CB, then it will contain bytes. All other values are undefined. [Currently they all produce a byte array. What are they?]
dim2
Encoding
C0 type8 arrayp16
Stack
( maxx , maxy : -)
Operation
Allocates an array.
A new two-dimensional array is allocated and the resource number is written to arrayp . The new array will have a maximum X index of maxx and a maximum Y index of maxy (i.e., maxy is one less than the size).
When allocating an array, if type is C7 then the array will contain words; if it is CB, then it will contain bytes. All other values are undefined. [Currently they all produce a byte array. What are they?]
MM C5 distObjectObject
MM C6 distObjectPt
MM C7 distPtPt
div
Encoding
17
Stack
( in1 , in2 : out )
Operation
out := in1 / in2
Performs a division operation on the stack. Note the order.
An attempt to divide by zero will cause undefined behavior, and may cause the interpreter to crash.
MM 83 doSentence
drawBox
Encoding
A6
Stack
( left , top , right , bottom , color : -)
Operation Draws a solid box on the backbuffer from ( left , top ) to ( right , bottom ) in the color color .
dup
Encoding 0C
Stack ( value : value , value )
Operation Duplicates the top-most item on the stack.
MM 67 endCutScene
MM 96 endOverride
eq
Encoding
0E
Stack
( value1 , value2 : bool )
Operation
If value1=value2 , set bool to 1, otherwise set it to 0
Tests the top two values on the stack to see if they are equal.
MM 81 faceActor
MM 92 findInventory
MM A0 findObject
freezeUnfreeze
Encoding
6A
Stack
( bool : -)
Operation
bool=0 :
Thaw all currently frozen threads.
0<bool<$80 :
Freeze all threads that are not marked as unfreezable.
bool³ $80 :
Freeze all threads, even those that are marked as unfreezable.
Freezing is a nestable operation; a thread which is frozen twice must be thawed twice before it becomes runnable again.
ge
Encoding
13
Stack
( value1 value2 : bool)
Operation
If value1³ value2 , set bool to 1, otherwise set it to 0
Compares the top two values on the stack. Note the order.
MM AB getActorAnimCounter1
MM 91 getActorCostume
MM A2 getActorElevation
MM 9F getActorFromXY
MM 8A getActorMoving
MM 8C getActorRoom
MM AA getActorScaleX
MM 90 getActorWalkBox
MM A8 getActorWidth
MM 93 getInventoryCount
MM 8F getObjectDir
MM 8D getObjectX
MM 8E getObjectY
MM 72 getOwner
getRandomNumber
Encoding
87
Stack
( max : result )
Operation A random number in the range 0 to max inclusive is calculated, and the result pushed onto the stack. The result is also written to the RandomNumber word variable (see 6.5).
getRandomNumberRange
Encoding 88
Stack ( min , max , : result )
Operation A random number in the range min to max inclusive is calculated, and the result pushed onto the stack. The result is also written to the RandomNumber word variable (see 6.5).
MM 8B getScriptRunning
MM 6F getState
MM A3 getVerbEntryPoint
MM 94 getVerbFromXY
gt
Encoding
10
Stack
( value1 , value2 : bool )
Operation
If value1 > value2 , set bool to 1, otherwise set it to 0
Compares the top two values on the stack. Note the order.
MM6D ifClassOfls
MM AF isActorInBox
isAnyOf
Encoding
AD
Stack
( arg1 , arg2 , arg3 , ..., argn , n , value : bool )
Operation
If value is any of arg1 .. argn , bool := 1, otherwise bool := 0
Tests to see if value is equal to any of the passed in arguments. If n is less than the number of entries on the stack, undefined behavior will result.
MM 98 isSoundRunning
MM 73 jump
Encoding
73 offset^16
Stack
(- : -)
Operation
pc := pc + offset
offset is added to the current program counter after the instruction has been decoded.
jumpFalse
Encoding
5D offset^16
Stack
( bool : -)
Operation
if bool = 0, pc := pc + offset
Pops the top value off the stack. If zero, then offset is added to the current program counter after the instruction has been decoded.
jumpTrue
Encoding
5C offset^16
Stack
( bool : -)
Operation
if bool 0, pc := pc + offset
Pops the top value off the stack. If non-zero, then offset is added to the current program counter after the instruction has been decoded.
kill
Encoding
1A
Stack
( value : -)
Operation
Pops the top value off the stack and discards it.
land
Encoding
18
Stack
( in1 in2 : out)
Operation
out:=in1 && in2
Performs a logical and operation on the stack (not a bitwise and). Note the order.
The boolean values are as in C, with 0 for false and non-zero for true.
le
Encoding
12
Stack
( value1 value2 : bool)
Operation
If value1£ value2 , set bool to 1, otherwise set it to 0
Compares the top two values on the stack. Note the order.
MM 7B loadRoom
MM 85 loadRoomWithEgo
lor
Encoding
19
Stack
( in1 in2 : out)
Operation
out:=in1 || in2
Performs a logical or operation on the stack (not a bitwise or). Note the order.
The boolean values are as in C, with 0 for false and non-zero for true.
lt
Encoding
11
Stack
( value1 value2 : bool)
Operation
If value1<value2 , set bool to 1, otherwise set it to 0
Compares the top two values on the stack. Note the order.
MM C9 miscOps
mul
Encoding
16
Stack
( in1 in2 : out)
Operation
out:=in1× in2
Performs a multiplication operation on the stack. Note the order.
neq
Encoding
0F
Stack
( value1 , value2 : bool )
Operation
If value1 value2 , set bool to 1, otherwise set it to 0
Tests the top two values on the stack to see if they are not equal.
MM 78 panCameraTo
pickOneOf
Encoding
CB
Stack
( index , arg0 , arg1 , arg2 , ..., argn , n : value )
Operation
value := arg[index]
Returns the index th argument on the stack. If n is less than the number of entries on the stack or index is out of range, undefined behavior will result, usually involving the interpreter shutting down.
pickOneOfDefault
Encoding
CC
Stack
( index , arg0 , arg1 , arg2 , ..., argn , n , default : value )
Operation
If index is in the range 0.. n , value := arg[index] ; otherwise value := default .
Returns the index th argument on the stack. If index is out of range, default is returned instead. If n is less than the number of entries on the stack, undefined behavior will result, usually involving the interpreter shutting down.
MM 84 pickupObject
MM B8 printActor
MM B9 printEgo
MM B4 print0
MM B5 print1
MM B6 print2
MM B7 print3
MM A1 psuedoRoom
pushByte
Encoding
00 value^8
Stack
(- : value )
Operation
Pushes value onto the stack. It is not sign extended.
pushByteVar
Encoding
02 pointer^8
Stack
(- : value )
Operation
Dereferences pointer and pushes the result onto the stack. Note that because pointer is encoded as a byte, it can only point to a word variable in the range 0000-00FF. Use pushWordVar for a more general version of this instruction.
pushWord
Encoding
01 value^16
Stack
(- : value )
Operation
Pushes value onto the stack.
pushWordVar
Encoding
03 pointer^16
Stack
(- : value )
Operation
Dereferences pointer and pushes the result onto the stack.
MM 80 putActorAtObject
MM 7F putActorInRoom
quitPauseRestart
This instruction varies according to the form.
Encoding
pause:
AE 9E
quit:
AE A0
Stack
(- : -) (both forms)
Operation Pauses and quits the game. [TODO: Details!]
MM 9B resourceRoutines
MM 9C roomOps
MM BF runScriptQuick
MM BE runVerbCodeQuick
MM A5 saveRestoreVerbs
MM 99 setBoxFlags
MM 7A setCameraAt
MM 6E setClass
MM 97 setObjectName
MM 61 setObjectState
MM 62 setObjectXY
MM 71 setOwner
MM 70 setState
MM AC soundKludge
MM 76 startMusic
MM 60 startObject
startScript
Encoding
5F
Stack
( script , arg0 , arg1 , arg2 , ..., argn , n : -)
Operation
A new thread is started, running the code in the script whose resource number is script. arg0 .. argn form the thread's initial local variables; unspecified variables are not initialised to any specific value.
The new thread starts executing immediately and the current thread is put into the PENDING state until the new thread is descheduled.
MM 5E startScriptEx
MM 74 startSound
MM 69 stopMusic
MM 65 stopObjectCode
MM 66 stopObjectCode
MM 77 stopObjectScript
MM 7C stopScript
MM B3 stopSentence
MM 75 stopSound
sub
Encoding
15
Stack
( in1 in2: out)
Operation out:=in1-in2
The top two items on the stack are popped off, the first subtracted from the second, and the result pushed back on the stack. Note the order.
MM BA talkActor
MM BB talkEgo
MM 9E verbOps
MM A9 wait
MM 75 walkActorTo
MM 7D walkActorToObj
wordArrayDec
Encoding
5B arrayp^16
Stack
( index : -)
Operation
arrayp [0, index ] := arrayp [0, index ] - 1
Increments the value at offset (0, index) in the array whose resource number is pointed to by arrayp.
wordArrayInc
Encoding
53 arrayp^16
Stack
( index : -)
Operation
arrayp [0, index ] := arrayp [0, index ] + 1
Increments the value at offset (0, index) in the array whose resource number is pointed to by arrayp.
wordArrayIndexedRead
Encoding
0B arrayp^16
Stack
( indexx , indexy : value )
Operation
value := arrayp [ indexx , indexy ]
Reads the value at offset (indexx, indexy) from the array whose resource number is pointed to by arrayp. The array can be a byte or word array; byte values are not sign extended.
wordArrayIndexedWrite
Encoding
4B arrayp^16
Stack
( indexx , indexy , value : -)
Operation
arrayp [ indexx , indexy ] := value
Writes value to the array whose resource number is pointed to by arrayp at offset (indexx, indexy). The array can be a byte or word array; when writing to a byte array, value is truncated.
wordArrayRead
Encoding
07 arrayp16
Stack
( index : value )
Operation
value := arrayp [0, index ]
Reads the value at offset (0, index) from the array whose resource number is pointed to by arrayp. The array can be a byte or word array; byte values are not sign extended.
wordArrayWrite
Encoding
47 arrayp^8
Stack
( index value : -)
Operation
arrayp [0, index ] := value
Writes value to the array whose resource number is pointed to by arrayp at offset (0, index). The array can be a byte or word array; when writing to a byte array, value is truncated.
wordVarDec
Encoding
57 pointer^16
Stack
(- : -)
Operation
* pointer := * pointer - 1
Decrements the variable pointed to by pointer.
wordVarInc
Encoding
4F pointer^16
Stack
(- : -)
Operation
* pointer := * pointer + 1
Increments the variable pointed to by pointer.
writeByteVar
Encoding
42 pointer^8
Stack
( value : -)
Operation
* pointer := value
Writes value to the variable pointed to by pointer. Note that as pointer is encoded as a byte, it can only point to word variables in the range 0x0000 to 0x00FF. For a more general form of this instruction, use writeWordVar.
writeWordVar
Encoding
43 pointer^16
Stack
( value : -)
Operation
* pointer := value
Writes value to the variable pointed to by pointer.
zero
Encoding
0D
Stack ( value : bool )
Operation
If value = 0, set bool to 1, otherwise set it to 0
Tests the value on the stack to see if it compares to zero.
All material © 2000-2002 David Given, unless where stated otherwise.