Z-machine version 6
Version 6 of the Z-machine is significantly different to all other versions. It adds graphics capabilities, but unfortunately, these are largely incompatible with Glk. As a result, version 6 of the Z-machine is not properly supported.
With that in mind, since the pool of existing Infocom V6 games is so small (Zork Zero, Shogun, Journey, and Arthur), it’s possible to special-case a lot of the graphics support for them. This deviates some from the normal operation, which is to treat games as a black box, simply executing their code without knowing or caring what game it is; but the result is playable V6 games which are a decent approximation of how they’re supposed to look and act.
This approach works, generally, because the games do predictable things with graphics in ways that can mostly be implemented in Glk. Instead of following the game’s instructions for graphics drawing, Bocfel will detect when and which graphics are being used, and draw things where it “knows” they’re supposed to be. On the other hand, the game’s input is used in some cases as well, so in the end, it’s a combination of listening to the game where that works, and overriding the game where necessary.
All version 6 Infocom games are generally complete in the sense that they can be played through without major problems.
Due to the nature of Glk, some aspects of the version 6 screen model are not possible to completely represent. Very notably this includes menus (such as hint menus) as well as mixing graphics and text (such as the status menu for Zork Zero). However, Gargoyle (currently in Git master) provides extensions to work around this, so if the Glk implementation is Gargoyle, graphics support is quite good.
To get graphics in these games, you will need Blorb files. The original Infocom games did not use Blorb, but the graphics have been converted to the Blorb format by Kevin Bracey. Moreover, the special-casing for version 6 games only applies to one version of each game; specifically, the versions of the games which the Blorb files reference. These are:
- Zork Zero: 393-890714
- Shogun: 322-890706
- Journey: 83-890706
- Arthur: 74-890714
Zork Zero and Arthur have some images which adapt their palette to the colors on the screen. Blorb handles this with its adapative palette chunk. This chunk requires that interpreters modify a PNG file’s palette on the fly, which Glk does not support, as it does not provide direct access to the images. Instead, Bocfel has support for the adaptive palette chunk via a Blorb extension. The official Blorbs on the IF Archive now include this extension.
Shogun notably does palette shifting but does not include an adaptive palette chunk in the official Blorbs. Included here is a modified Shogun Blorb that includes Bocfel’s extension for adaptive palettes.
Last Blorb update: September 6, 2026.
Finally, most testing has been done with interpreter number 1. Other interpreter numbers might work just as well, or might not. If there are defects with specific interpreter numbers, feel free to leave a bug report.
In addition to Infocom games, Brian Howarth’s Mysterious Adventures games were converted to version 6 Z-code by Colin Davies, and include graphics support. Bocfel also has special-cased support for these games. Aldo Cumani also converted these games to Z-code, with graphics drawn directly by the game instead of through Blorb files. These are unsupported.