Quetzal file format


Quetzal is a standardised file format for the saved state of Z-machine games, invented by Martin Frost. Prior to the introduction of Quetzal, each Z-machine interpreter saved games in its own format; Quetzal enabled players to save a game using one interpreter and restore it with another. Use of the format is strongly recommended in Graham Nelson's Z-machine standards document, but not obligatory. Most modern Z-machine interpreters have the ability to save Quetzal files.
The files are IFF files with a FORM of "IFZS", although the saved files are commonly given an extension of ".sav": less commonly sighted are "quz" and "qtz". Despite the reference to the Z-machine in the FORM code, the format has proved flexible enough to be adapted for at least one alternative architecture, Glulx.
The magic-number reading of the files are often shown as:
'IFF data, Z-machine or Glulx saved game file '

A backronym for the format is "Quetzal Unifies Efficiently The Z-Machine Archive Language".
Version 1.3b, which was widely available, contained a bug later corrected in version 1.4: after a save instruction, the Z-machine requires that a success code is saved in a particular place. Versions of the Quetzal standard before 1.4 have reference only to the instruction after the save, which complicates finding the correct place to put the success code.