The following conventions are used in the encoding descriptions.
- opcode
-
The instruction's opcode, with the appropriate bits set according to the
parameters.
- result
-
A result pointer. (A standard word pointer, always a LE word.)
- value[8]
-
An 8-bit constant (a byte).
- value[16]
- A 16-bit constant (a word LE).
- value[p8]
- An 8-bit parameter. This may be encoded as a word
LE if it's a pointer, or a byte if it's a constant.
- value[p16]
- A 16-bit parameter. This is always encoded as
a word LE.
- value[v16]
- A variable number of word LE parameters. These are encoded as a sequence of
aux[8] param[p16]; param; aux contains the parameter bit
to describe param. A byte of $FF terminates the sequence.
- value[o]
- The offset word for parameter value. This
is only encoded if needed, but always at the position indicated. If
not specified, the offset word occurs immediately after the parameter.
- (term)
- An optional term.
actorFollowCamera
$52
actorFromPos
$15
actorFollowCamera
$52
actorFromPos
$15
actorSet
$13
actorSetClass
$5D
add
$5A; one parameter, uses result
Encoding
opcode result value[p16]
Operation
result := result + value
The variable pointed to by result is read, value is
added to it, and the result written back.
and
$17; one parameter, uses result
Encoding
opcode result value[p16]
Operation
result := result and value
The variable pointed to by result is read, logically ANDed with
value, and the result written back.
animateActor
$11
arrayOp
$27; parameters depend on auxiliary opcode
Encoding
opcode $01 array[p8]
opcode $02 dest[p8] src[p8]
opcode $03 array[p8] index[p8] data[p8]
opcode $04 result array[p8] index[p8]
opcode $05 array[p8] size[p8]
Operation
Miscellaneous actions on Arrays (referred to by resource number).
| Opcode | Meaning | Description |
|---|
| $01 |
load array |
Ensures that the Array is loaded into memory. [I don't know what this does.]
|
| $02 |
copy array |
Creates a duplicate of src at resource number dest. The old Array
at dest is lost.
|
| $02 |
copy array |
Creates a duplicate of src at resource number dest. The old Array
at dest is lost.
|
| $03 |
write entry |
Writes the byte data at offset index of Array array. Out
of bounds accesses cause undefined behaviour.
|
| $04 |
read entry |
Sets result to the byte of data at offset index of Array
array. Out of bounds accesses cause undefined behaviour.
|
| $05 |
create entry |
Allocates or frees an Array. The Array array is initialised to size size; if size is zero, the Array is freed.
|
breakHere
$80; no parameters
Encoding
opcode
Operation
Deschedules the currently running thread. Execution continues at the next
instruction when the thread's next timeslot comes around.
chainScript
$42; one parameter plus varargs
Encoding
opcode script[p8] args[v16]...
Operation
Replaces the currently running script with another one. The current script is
terminated immediately and the new script, resource number script, is
executed in the same thread. The new script has its local variables initialised
to the list args. Uninitialised variables have undefined values.
cursorCommand
$2C
cutScene
$40
debug
$6B; one parameter, no result
Encoding
opcode param[p16]
Operation
Passes the parameter to the interpreter's debugger. What this does is entirely
platform-specific (and may do nothing).
decrement
$C6; no parameters, uses result
Encoding
opcode result
Operation
result := result - 1
Reads the variable pointed to by result, decrements it, and writes it back.
delay
$2E; one constant parameter
Encoding
opcode param[24]
Operation
Suspends the current thread for the appropriate number of 1/60ths of a second. Yes, that really is a 24-bit LE constant.
delayVariable
$2E; one constant parameter
Encoding
opcode pointer[16]
Operation
pointer is dereferenced and the current thread suspended for that number of 1/60ths of a second. Note that pointer is an inline constant, not a parameter.
divide
$5B; one parameter, uses result
Encoding
opcode result value[p16]
Operation
result := result / value
The variable pointed to by result is read, divided by value, and
the result written back. If value is zero, the result is undefined (and
the interpeter may halt with an error).
doSentence
$19
drawBox
$3F; two parameters, does not use result, supplementary opcode byte with three more subsequent parameters
Encoding
opcode left[p16] top[p16] auxopcode[8] right[p16] bottom[p16] colour[p8]
Operation
Draws a solid box on the backbuffer from (left,
top)-(right, bottom) in the colour colour.
The only part of auxopcode that is relevant are the parameter bits.
The rest of the opcode is ignored.
drawObject
$05
dummy
$67
endCutScene
$C0
equalZero
$28
expression
$AC
faceActor
$09
findInventory
$3D
findObject
$35
freezeScripts
$60
getActorCostume
$71
getActorElevation
$06
getActorFacing
$63
getActorMoving
$56
getActorRoom
$03
getActorScale
$3B
getActorWalkBox
$7B
getActorWidth
$6C
getActorX
$43
getActorY
$23
getAnimCounter
$22
getClosestObjActor
$66
getDist
$34
getInventoryCount
$31
getObjectOwner
$10
getObjectState
$0F
getRandomNumber
$16
getScriptRunning
$68
getVerbEntryPoint
$0B
ifClassOfIs
$1D
increment
$46; no parameters, uses result
Encoding
opcode result
Operation
result := result + 1
Reads the variable pointed to by result, increments it, and writes it back.
isActorInBox
$1F
isEqual
$48
isGreater
$78
isGreaterEqual
$04
isLess
$44
isNotEqual
$08
isSoundRunning
$7C
jumpRelative
$18; non-standard encoding
Encoding
opcode target[16]
Operation
PC := PC + target
The inline constant target is read as a signed word and added to the
program counter after the instruction has been read. Therefore, if
target is zero, the instruction will do nothing; if target is -3,
an infinite loop will result.
lessOrEqual
$38
lights
$70
loadRoom
$72
loadRoomWithEgo
$24
matrixOp
$30
move
$1A
multiply
$1B
notEqualZero
$A8
or
$57; one parameter, uses result
Encoding
opcode result value[p16]
Operation
result := result and value
The variable pointed to by result is read, logically ORed with
value, and the result written back.
overRide
$58
panCameraTo
$12
pickupObject
$25
print
$14
printEgo
$D8
pseudoRoom
$CC
putActor
$01
putActorAtObject
$0E
putActorInRoom
$2D
quitPauseRestart
$98
resourceRoutines
$0C
roomOp
$33
saveRestoreVerbs
$AB
setCameraAt
$32
setObjectName
$54
setOwnerOf
$29
setState
$07
setVarRange
$26
soundKludge
$4C
startMusic
$02
startObject
$37
startScript
$0A; one parameter plus varargs, extra encoding in opcode
Encoding
opcode script[p8] args[v16]...
Operation
Spawns a new thread running the code in script script. The new script has its local variables initialised to the list args. Uninitialised variables have undefined values.
The opcode carries extra information:
If the Q bit is set, the new thread is marked as quick. If the
F bit is set, the thread is marked as unfreezable. The P1
bit is the parameter bit for script, as usual.
startSound
$1C
stopMusic
$20
stopObjectCode
$00
stopObjectScript
$6E
stopScript
$62
stopSound
$3C
subtract
$3A
animateActor
$11
wait
$AE
walkActorTo
$1E
walkActorToActor
$0D
walkActorToObject
$36
All material © 2000-2002 David Given, unless where stated otherwise.
