Sierra Creative Interpreter

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The SCript Interpreter or later, Sierra Creative Interpreter, (SCI), or as it later became known as, Sierra Creative Interpreter, is the scripting language created by Jeff Stephenson of Sierra On-Line for its adventure games. It was the successor of Sierra's earlier interpreter, AGI, and the runtime environment for such adventure games. Although ports for the Amiga, Atari ST, Macintosh and PC-9801 platforms exist, the primary development was for the IBM PC platform.



While AGI was a procedural language, SCI is completely object-oriented. For more detailed information, see the SCI Specifications.



Although continuously developed between 1988 and 1996, five major versions can be isolated:



First used for King's Quest IV: The Perils of Rosella in 1988, SCI0 ( allowed for 320×200 graphics with 16 colors as well as a music-card compatible soundtrack. It also supported parser-based keyboard input which a game could be scripted to use if it wishes to do so (non-adventure games usually didn't).

SCI0 Resources

The resource types of SCI0 can be roughly grouped into four sets:

Games using SCI0

(in order of release):


Later versions of SCI0 added bilingual support for international versions; their version string reads "". Games include:



The last SCI0 game, Jones in the Fast Lane, already used the graphics engine from SCI1 and thus was available in a 256 color version.



Quest for Glory II has been falsely identified by some as SCI1, but is actually SCI01. Perhaps this is because its debug reports SCI version 1.000.*** even when the interpreter itself is 0.001.0**.

"Quest for Glory II definitely did *not* use the SCI1 interpreter that Sierra used for King's Quest V and the other 256-color EGA games. That interpreter did not have a parser, so could not handle typed input at all. If they internally called QfG2's interpreter 'SCI1', it was just a PR thing - It was not the same interpreter.

"As to *why* QfG2 used the parser and EGA graphics, it's because all of Sierra's other games were running late. Sierra needed a major release for Christmas 1990, and we were the sacrificial lamb. (I think it was partially because I did not fight as hard as Mark Crowe - The choice was between QfG2 and SQ3 as to which game would ship early, but with 16-color graphics.)"

-- Corey Cole

SCI0.1 extensions

SCI01 differs only in very few respects: It uses different compression algorithms and a different type of sound resources, which may contain digitized sound effects (PCM data). The basic music data, however, still resembles MIDI data.

Also, scripts are split into two parts when loaded: A dynamic part, which resides in the heap as before, and a static part, which is stored externally to conserve heap space.[1]

Games using SCI0.1

(in order of release):


Released in 1990, the most notable improvement in SCI1 ( was the support of 256 color graphics, still at a resolution of 320×200; EGA 16 color graphics were still available (games were usually sold in separate 16 and 256 color versions). Some people prefer to call the 16-color SCI1 interpreters "SCI01". With the shift to SCI1, Sierra began using a digitized painting process for background artwork, rather than the pixel-by-pixel process of previous engines: the difference is readily apparent if one compares, for example, King's Quest 4 against King's Quest 5.

Most SCI1 games are completely mouse-driven, using an icon-based interface; contrary to popular thought, it is up to the game's script code, not to the interpreter, to implement the user interface. For example, even though Quest for Glory 2 is parser-driven and King's Quest 5 is mouse-driven, they use compatible interpreters, as it is possible to use the interpreter from QFG2 with the EGA version of KQ5.

The version numbering scheme is somewhat confusing for the reason that the third number in the version string (the build number) has only three digits, even though four are needed. For example, the game Space Quest 4 Version 1.052 ships with an interpreter labeled "1.000.753", whereas the game Conquests of the Longbow Version 1.0 ships with an interpreter labeled "1.000.168"; nevertheless, the latter interpreter is newer because the build number is actually 1168, not 168. Also, in some cases the "1.000" is replaced with "T.A00", which however does not indicate a separate development fork.

SCI1 extensions

SCI1 introduced new concepts like Palettes, scaled bitmap images and several new compression algorithms. In SCI1.0, the resource limit was first increased to 16383[2], and then to 65535 in SCI1. Because of the inherent limitations of the FAT file system the primary target OS of Sierra's SCI interpreter was limited to, patch file names were altered accordingly, with the resource number (not padded) before the dot and a three-letter resource ID behind it; examples are "0.scr" or "100.v56".

The complete list of suffixes is as follows:

  • 80: V56: 256 color views
  • 81: P56: 256 color background pictures
  • 82: SCR: Scripts (static data)
  • 83: TEX: Texts (deprecated in favor of messages)
  • 84: SND: Sound data (MIDI music)
  • 85: No extension: Type 0x85 resources are 'memory' resources, which are only used internally.
  • 86: VOC: Vocabulary (not used)
  • 87: FON: Fonts
  • 88: CUR: Mouse cursors (deprecated in favor of v56-based cursors)
  • 89: PAT: Audio patch files
  • 8a: BIT: Bitmap files (purpose unknown)
  • 8b: PAL: 256 color palette files
  • 8c: CDA: CD Audio resources
  • 8d: AUD: Audio resources (voice and digital sound effects)
  • 8e: SYN: Sync (purpose unknown)
  • 8f: MSG: Message resources: Text plus metadata
  • 90: MAP: Map (purpose unknown)
  • 91: HEP: Heap resources: Dynamic script data
  • ??: SEQ: Sequence resources for cut scenes

Apparently, the script resource split introduced in SCI01 was incorporated into the actual resource layout in SCI1.

Games using SCI1

(in order of release):

Interpreters with build numbers >1000 have slightly modified file formats and improved foreign language support (resulting from a code merge with SCI0's S.OLD fork), but are otherwise like earlier SCI1 versions. Games include:


Apart from considerable internal changes, SCI1.1 ( added support for animated movie sequences (first used in KQ6) as well as scaling sprites: characters would become smaller as they walk into the distance, giving a pseudo-3D effect. (The interpreters from some early SCI1.1 games bear a "2.000.000" version stamp; this is most likely an inconsistency which should be ignored.)

Separate 16-color packages were no longer available; EGA owners instead would be presented a 640×200 graphics display that simulated 256 colors via dithering.

SCI1.1 extensions


Games using SCI1.1

(in order of release):


Often called SCI32 (along with SCI3), SCI2 ( runs in 32-bit mode by using the DOS/4GW extender or by running it in Windows 3.1's Win32s. Most notable is the support of high-resolution 640×480 graphics, as well as better movie support. There are two known revisions, 2.000.000, and 2.100.002. Games include:

SCI2 extensions


Games using SCI2

(in order of release):



SCI2.1 extensions

Early versions used a modified SCI2 kernel table. Most of these games maintain the "old school" Sierra graphics. Robot videos were introduced, in the DOS version of KQ7.

Middle versions include the finalized kernel function table, the addition of VMD video resource and a more heavy usage of RBT (robot) videos. Graphics in these games were generally either cartoonish or 3D pre-rendered from filmed actors.

Games using SCI2.1

(in order of release):


A.K.A. "SCI32" The last version, SCI32 (3.000.000) could not only run under DOS or Windows 3.1, but also natively under Windows 95.

SCI3 extensions

Middle versions include the finalized kernel function table (which was also used in the SCI3 games)

Games using SCI3

(in order of release):



Some Sierra games used SCI resources, such as graphics and sounds, but did not use the SCI script interpreter itself. Games include:


Related software

SCI editors can be used to uncover unfinished game elements that had been concealed in the game's resource files by the developer during the game's development. These hidden resources include unfinished artworks, puzzles, scenery, voiceover or music recordings as well as gags inserted by the development team. [3] Examples of game titles from which such hidden resources have been uncovered include King's Quest V: Absence Makes the Heart Go Yonder (SCI1.1), Space Quest IV: Roger Wilco and the Time Rippers (SCI1.1), Leisure Suit Larry 6: Shape Up or Slip Out! (SCI1.1), King's Quest VII: The Princeless Bride (SCI2), and Space Quest 6: The Spinal Frontier (SCI2).


See Also



  1. The background for this is that heap space started running out in Quest for Glory 2. In order to compensate for this, changes were made to both the script library and the interpreter.
  2. This appears to be the limit- none of the SCI1.0 games tested used resource numbers beyond 16383
  3. Beebe, Jess (2008-08-18) "Resource Quest: hidden treasures in Sierra’s adventure games" Adventure Classing Gaming Retrieved 2008-09-14


External Links