Lingo bytecode

File Format
Name	Lingo bytecode
Ontology	Electronic File Formats Development Lingo bytecode

This is a partial, work-in-progress examination of the bytecode created when Lingo code is compiled in Macromedia Director 4.0. It describes instructions for a stack-based virtual machine. This virtual machine is sometimes known as the IML, or Idealized Machine Layer.

Each instruction is one, two or three bytes.

• If the first byte is in the range 0x00-0x3F, then the full instruction is one byte.
• If the first byte is in the range 0x40-0x7F, then the full instruction is two bytes.
• If the first byte is in the range 0x80-0xFF, then the full instruction is three bytes.

Constant blobs like string literals are stored after the bytecode, and referred to by records that are six bytes long regardless of the actual length of the data. This means the first constant will be referred to as 0x00, the second constant as 0x06, the third as 0x0C, and so on. Integer literals over 32767 and floating-point number literals are also stored as constants.

There is also a namelist for referring to external identifiers, stored separately from the bytecode. This is a simple array of strings.

One-Byte Instructions

01	exit			Leave the current function immediately and return to its caller. Automatically added as the final step of a function.
02
03	0 FALSE		+1	Push zero onto the stack.
04	(a * b)	-2	+1	Pop two values from the stack, multiply them together and push the result.
05	(a + b)	-2	+1	Pop two values from the stack, add them together and push the result.
06	(a - b)	-2	+1	Pop two values from the stack, subtract the second from the first and push the result.
07	(a / b)	-2	+1	Pop two values from the stack, divide the first by the second and push the result.
08	(a mod b)	-2	+1	Pop two values from the stack, perform a modulo operation and push the result.
09	(-a)	-1	+1	Pop one value from the stack, negate it and push the result.
0A	(a & b)	-2	+1	Pop two values from the stack, concatenate them and push the resulting string.
0B	(a && b)	-2	+1	Pop two values from the stack, concatenate them with one space character added in between, and push the resulting string.
0C	(a < b)	-2	+1	Pop two values from the stack, push 1 if the first is less than the second and 0 if not.
0D	(a <= b)	-2	+1	Pop two values from the stack, push 1 if the first is less than or equal to the second and 0 if not.
0E	(a <> b)	-2	+1	Pop two values from the stack, push 0 if the two values are the same and 1 if they are not.
0F	(a = b)	-2	+1	Pop two values from the stack, push 1 if the two values are the same and 0 if they are not.
10	(a > b)	-2	+1	Pop two values from the stack, push 1 if the first is greater than the second and 0 if not.
11	(a >= b)	-2	+1	Pop two values from the stack, push 1 if the first is greater than or equal to the sceond and 0 if not.
12	(a and b)	-2	+1	Pop two values from the stack, push 1 if both are logically true and 0 if not.
13	(a or b)	-2	+1	Pop two values from the stack, push 1 if either are logically true and 0 if not.
14	(not a)	-1	+1	Pop one value from the stack, push 0 if it is logically true and 1 if not.
15	(a contains b)	-2	+1	Pop two values from the stack, push 1 if the first is a string that contains the second and 0 if not. The text comparison is case-insensitive and ignores diacritic marks, e.g. "a" and "Å" are treated the same.
16	(a starts b)	-2	+1	Pop two values from the stack, push 1 if the first is a string that begins with second string and 0 if not. The text comparison is case-insensitive and ignores diacritic marks, e.g. "a" and "Å" are treated the same.
17	(char a of c) (char a to b of c) (item 1 to 3 of someItems)	-9	+1	String slice/split operation. It takes nine arguments from the stack: -9 First char position -8 Last char position -7 First word position -6 Last word position -5 First item position (items separated by the itemDelimiter, which is a comma by default) -4 Last item position -3 First line position -2 Last line position -1 The string to slice The positions used here are one-based, so zero is invalid as a position and is instead used to indicate unused parameters. Only one "first X position" can be set, the rest must be zero. The corresponding "last X position" may either be set too, or it can be zero, in which case the first position will also be used as the last.
18	hilite word 1 of field 10	-9		Highlight (select) some text. The nine arguments taken from the stack are: -9 First char position -8 Last char position -7 First word position -6 Last word position -5 First item position -4 Last item position -3 First line position -2 Last line position -1 Field number (cast ID) The positions used here are one-based, so zero is invalid as a position and is instead used to indicate unused parameters. Only one "first X position" can be set, the rest must be zero. The corresponding "last X position" may either be set too, or it can be zero, in which case the first position will also be used as the last.
19	(sprite 1 intersects 2)	-2	+1	Pop two sprite IDs and push 1 if the bounding rectangles of the two sprites touch at all, or 0 if they do not.
1A	(sprite 1 within 2)	-2	+1	Pop two sprite IDs and push 1 if the bounding rectangle of the first is entirely inside the bounding rectangle of the second, or 0 if not.
1B	(field 1)	-1	+1	Pop a cast ID (name or number), push the value of that cast member's text property.
1C	tell someObject to go to frame 1	-1		Pop an object from the stack and begin running subsequent bytecodes in the context of that object, until code 1D is encountered.
1D	tell someObject to go to frame 1			Marker for the end of a sequence of bytecodes started by 1C. Similar to 01 except for nested bytecode chunks instead of the main one.
1E		-1	+1	Some kind of list transformation or check, seen used just before setting the actorList to []. More research is needed to know exactly what is happening there.
1F	[#key: value]	-1	+1	Pops a list that must be in the form [#symbol1, val1, #symbol2, val2 ...] to transform into [#symbol1: val1, #symbol2: val2 ...]

Two-Byte Instructions

41 XX	1 .. 127		+1	Push integer of value XX, which must be between 1 and 127, inclusive. To push zero, use 03. To push larger integers, use 81 XX YY.
42 XX	a, b, c	-XX	+1	Pop the specified number of values off the top of the stack, create an unparenthesized argument list containing them (i.e. for a call statement like myFunction 1, 2, 3), and push that to the stack.
43 XX	[a, b, c]	-XX	+1	Pop the specified number of values off the top of the stack, create a list for them (which can also be used for a parenthesized call expression like set result = myFunction(1, 2, 3)), and push that to the stack.
44 XX	"literal" 0.5 32768		+1	Push a constant from local constant records onto the stack. These records seem to be six bytes long (regardless of the actual size of the constant value), so pushing the first one is 44 00, the second is 44 06, the third is 44 0C, etc.
45 XX	#symbol		+1	Push a symbol with a name from namelist[XX]. Note that the name will be stored as "name", not "#name".
46 XX
47 XX
48 XX
49 XX	(someGlobal) where previously declared: global someGlobal		+1	Push the value of a global variable with a name from namelist[XX].
4C XX	(someLocal)		+1	Push the value of a local variable. The local variable records seem to be 6 bytes long, so the first is pushed with 4C 00, the second with 4C 06, etc.
4D XX
4E XX
4F XX	set someGlobal = 0	-1		Pop one value and use it to set the global variable with name from namelist[XX].
50 XX
51 XX
52 XX	set someLocal = 0	-1		Pop one value and use it to set a local variable. See code 4C 00 for a note about local variable records.
53 XX
54 XX	end repeat			Unconditional backwards jump by XX bytes, relative to the first byte of this instruction.
55 XX
56 XX	localFunction(1,2,3)	-1	+1 or +0	Call a function defined in this script with the name at namelist[XX]. The top value on the stack must be an argument list. If the argument list was created with code 43 XX, one return value will be pushed to the stack. If the argument list was created with code 42 XX, no return value will be pushed.
57 XX	someFunction 1,2,3 (someFunction(1,2,3))	-1	+1 OR +0	Call the external function with name from namelist[XX]. The top value on the stack must be an argument list. If the argument list was created with code 43 XX, one return value will be pushed to the stack. If the argument list was created with code 42 XX, no return value will be pushed.
58 XX
59 16	put "extra" into textVar	-1		(Not sure how the target value is specified, needs more research)
59 25	put "extra" after textVar	-1		(See above)
59 35	put "extra" before textVar	-1		(See above)
5A XX
5B 05	delete word 3 of textVar	-1		(See above)
5C 00	(the abbr time) (the short date) (the last word in someText)	-1 OR -2	+1	If the top value is one of the following setting IDs, pop it from the stack, and push the current value of the setting: 00 the floatPrecision 01 the mouseDownScript 02 the mouseUpScript 03 the keyDownScript 04 the keyUpScript 05 the timeoutScript If the top value is a time-formatting ID, pop it from the stack, and push the current time formatted using it: 06 the short time 07 the abbreviated time, the abbrev time, the abbr time 08 the long time If the top value is a date-formatting ID, pop it from the stack, and push the current date formatted using it: 09 the short date 0A the abbreviated date, the abbrev date, the abbr date 0B the long date If the top value is a slice type ID, pop both it and the previous value from the stack. The previous value will be a string, slice the last "bit" of it according to the slice type, and push the sliced value: 0C the last char 0D the last word 0E the last item 0F the last line
5C 01	(the number of chars in someText)	-2	+1	Pop [text, stat ID] and push the stat value for the given text, using these stat IDs: 01 chars 02 words 03 items (separated by the itemDelimiter, which is a comma by default) 04 lines
5C 02	(the name of menu 1)	-2	+1	Pop [menu ID, property ID] and push the value of the specified menu property, using these property IDs: 01 name 02 number of menuItems
5C 03	(the name of menuItem 3 of menu 1)	-3	+1	Pop [item ID, menu ID, property ID] and push the value of the specified menu item property, using these property IDs: 01 name 02 checkMark 03 enabled 04 script
5C 04	(the volume of sound 1)	-2	+1	Pop [sound ID, property ID] and push the value of the specified sound property, using these property IDs: 01 volume (0 to 255)
5C 06	(the cursor of sprite 3)	-2	+1	Pop [sprite ID, property ID] and push the value of the specified sprite property, using these property IDs: 01 type 02 backColor 03 bottom 04 castNum 05 constraint 06 cursor 07 foreColor 08 height 0A ink 0B left 0C lineSize 0D locH 0E locV 0F movieRate 10 movieTime 12 puppet 13 right 14 startTime 15 stopTime 16 stretch 17 top 18 trails 19 visible 1A volume (-256 to 256, <= 0 is silent) 1B width 1D scriptNum 1E moveableSprite 20 scoreColor The values for type are: 0 inactive 1 bitmap 2 rectangle 3 rounded rectangle 4 oval 5 line top-left to bottom-right 6 line bottom-left to top-right 7 text 8 button 9 checkbox 10 radio button 16 undetermined (try the castType of the associated cast member)
5C 07	(the exitLock)	-1	+1	Pop a setting ID from the stack and push its value, using these setting IDs: 01 the beepOn 02 the buttonStyle 03 the centerStage 04 the checkBoxAccess 05 the checkBoxType 06 the colorDepth 08 the exitLock 09 the fixStageSize 13 the timeoutLapsed 17 the selEnd 18 the selStart 19 the soundEnabled 1A the soundLevel 1B the stageColor 1D the stillDown 1E the timeoutKeyDown 1F the timeoutLength 20 the timeoutMouse 21 the timeoutPlay 22 the timer
5C 08	(the number of castMembers)	-1	+1	Pop a stat ID from the stack and push the stat, using these stat IDs: 02 number of castMembers 03 number of menus
5C 09	(the picture of cast "bob") (the name of cast 3)	-2	+1	Pop [cast ID, property ID] from the stack and push the value of the cast property, using these property IDs: 01 name 02 text 08 picture 0A number 0B size 11 foreColor 12 backColor
5C 0C	(the textSize of field 1)	-2	+1	Pop [field ID, property ID] and push the value of the property for the given field according to these property IDs: 03 textStyle 04 textFont 05 textHeight 06 textAlign 07 textSize
5C 0D	(the sound of cast 5)	-2	+1	Pop [cast ID, property ID] and push the value of property for the given cast according to these property IDs: 10 sound
5D 00	when keyDown then beep	-2		Pop [statement, eventID] and set the statement (Lingo source code in a text string) to run on the given event: 01 mouseDown 02 mouseUp 03 keyDown 04 keyUp 05 timeOut
5D 03	set the enabled of menuItem 3 of menu 5 to FALSE	-4		Pop [menuItem ID, menu ID, new value, property ID] and set the menu item property. See the table for code 5C 03 for menu item property IDs.
5D 04	set the volume of sound 3 to 255	-3		Pop [sound ID, new value, property ID] and set the menu item property. See the table for code 5C 04 for sound property IDs.
5D 06	set the constraint of sprite 3 to 0	-3		Pop [sprite ID, new value, property ID] and set the sprite property. See the table for code 5C 06 for sprite property IDs.
5D 07	set the exitLock to TRUE	-2		Pop [new value, setting ID] and change the relevant setting. See the table for code 5C 07 for setting IDs.
5D 09	set the backColor of cast "bob" to 0	-3		Pop [cast ID, new value, property ID] and set the cast property. See the table for code 5C 09 for cast property IDs.
5D 0C	set the textAlign of field 3 to "right"	-3		Pop [field ID, new value, property ID] and set the field property. See the table for code 5C 0C for cast property IDs.
5D 0D	set the sound of cast 3 to TRUE	-3		Pop [cast ID, new value, property ID] and set the cast property. See the table for code 5C 0D for cast property IDs.
5E XX
5F XX	(the someProperty)		+1	Push the value of the contextual property with the name at namelist[XX].
60 XX	set the someProperty to 0	-1		Pop a value and use it to set the contextual property with the name at namelist[XX].
61 XX	(the someProperty of someVariable)	-1	+1	Pop a property-owning object from the stack, and push the value of this object's property with the name at namelist[XX].
62 XX	set the someProperty of someVariable to 1	-2		Pop [property-owning object, new value] from the stack and set the property of the object with the name at namelist[XX].
63 XX	tell someObject to go to frame 1	-1		Remote call: Similar to 57 XX except runs in the context of a tell ... to block.
64 XX			+1	Push a copy of a value already on the stack, relative to the top where 00 is the top slot, 01 is one slot beneath the top, etc. This is used by the compiler when generating bytecode for the repeat with i in list block, to keep state in the loop without allocating new local variables.
65 XX		-XX		Pop and discard XX values from the top of the stack. This is used in the bytecode generated for a repeat with i in list block, to clean up at the end.
66 04	(the machineType)	-1	+1	Pop an empty list off the stack and push an ID representing the type of computer that we are running on: 1 Macintosh 512Ke 2 Macintosh Plus 3 Macintosh SE 4 Macintosh II 5 Macintosh IIx 6 Macintosh IIcx 7 Macintosh SE/30 8 Macintosh Portable 9 Macintosh IIci 11 Macintosh IIfx 15 Macintosh Classic 16 Macintosh IIsi 17 Macintosh LC 18 Macintosh Quadra 900 19 PowerBook 170 20 Macintosh Quadra 700 21 Classic II 22 PowerBook 100 23 PowerBook 140 24 Macintosh Quadra 950 25 Macintosh LCIII 27 PowerBook Duo 210 28 Macintosh Centris 650 30 PowerBook Duo 230 31 PowerBook 180 32 PowerBook 160 33 Macintosh Quadra 800 35 Macintosh LC II 42 Macintosh IIvi 46 Macintosh II vx 47 Macintosh Color Classic 48 PowerBook 165c 50 Macintosh Centris 610 52 PowerBook 145 76 Macintosh Quadra 840av 256 IBM PC-type machine
66 05	(the pathName)	-1	+1	Pop an empty list and push a string containing the full OS path of the folder which contains the current movie file.
66 2E	(the date)	-1	+1	Pop an empty list off the stack and push the current date with default formatting (same as "the short date").
66 3C	(the time)	-1	+1	Pop an empty list off the stack and push the current time with default formatting (same as "the short time").

Three Byte Instructions

81 XX YY	128 .. 32767		+1	Push the integer ((XX * 0x100) + YY). Larger integers and floats are pushed using constants.
82 XX YY	someFunc 1, 2, 3, (...) 254, 255, 256, 257	-((XX * 0x100) + YY)	+1	Pop ((XX * 0x100) + YY) values from the stack and push a no-return-value argument list object containing these values. Similar to code 42 XX, only necessary when there are more than 255 arguments in the list.
83 XX YY	[1, 2, 3, (...) 254, 255, 256, 257]	-((XX * 0x100) + YY)	+1	Pop ((XX * 0x100) + YY) values from the stack and push a list object containing these values. Similar to code 43 XX, only necessary when there are more than 255 items in the list.
93 XX YY	else exit repeat next repeat			Unconditional jump: Advance by ((XX * 0x100) + YY) bytes, relative to the first byte of this instruction (i.e. it may be 3 more than you are expecting) (next repeat jumps forward to end repeat instead of jumping back itself)
95 XX YY	if somethingIsTrue then repeat while somethingIsTrue	-1		Conditional jump: Pop a value, and if it is logically FALSE, advance by ((XX * 0x100) + YY) bytes, relative to the first byte of this instruction

Syntactic Sugar

Some functions get special syntax when written out in source code, but under the hood, the compiler just transforms it into more regular syntax. Here is a mapping that shows the equivalent in plain, generalized Lingo that gets used for the bytecode.

Specialized Syntax	Generalized Syntax
play frame 10 of movie "theMovie"	play 10, "theMovie"
play frame 10	play 10
play movie "theMovie"	play 1, "theMovie"
play done	play
repeat with i = 15 to 20 ... end repeat	set i = 15 repeat while i <= 20 ... set i = i + 1 end repeat
repeat with i = 15 down to 10 ... end repeat	set i = 15 repeat while i >= 10 ... set i = i - 1 end repeat
sound fadeIn 5	sound #fadeIn, 5
sound fadeIn 5, 10	sound #fadeIn, 5, 10
sound fadeOut 5	sound #fadeOut, 5
sound fadeOut 5, 10	sound #fadeOut, 5, 10
sound playFile 1, "Thunder"	sound #playFile, 1, "Thunder"
sound close 1	sound #close, 1
go to frame 10 go frame 10 go to 10	go 10
go to movie "theMovie" go movie "theMovie"	go 1, "theMovie"
go to frame 10 of movie "theMovie" go frame 10 of movie "theMovie" go to 10 of movie "theMovie" go 10 of movie "theMovie"	go 10, "theMovie"
go loop	go #loop
go next	go #next
go previous	go #previous
open "document" with "application"	open "document", "application"

Lscr bytecode-container chunk layout

Header

...
$0040-$0041	uint16	Offset to the function records block
...
$0048-$0049	uint16	Number of function records
...

Function Record

Each function record is 42 bytes long.

$0000-$0001	uint16	Namelist index for the function's name, or 0xFFFF if there is no name(?)
$0002-$0003	uint16	Unknown
$0004-$0007	uint32	Length of the function bytecode in bytes
$0008-$000B	uint32	Offset to the function bytecode
$000C-$000D	uint16	Number of arguments
$000E-$0011	uint32	Unknown
$0012-$0013	uint16	Number of local variables
$0014-$0017	uint32	Unknown
$0018-$0019	uint16	Count (C)
$001A-$001D	uint32	Unknown
$001E-$0021	uint32	Unknown
$0022-$0023	uint16	Unknown
$0024-$0025	uint16	Count (D)
$0026-$0029	uint32	Unknown

Bytecode Trailer

After the bytecode section for a function (determined using the offset and length fields from the function record), and then after an additional padding byte if there are an odd number of bytes in the bytecode, are the following values:

• For each argument: uint16 namelist index for the argument's name
• For each local variable: uint16 namelist index for the variable's name
• Count (C) * uint16
• Count (D) * uint8
• A padding byte if Count (D) is an odd number