§1. The Inform system of today sometimes uses the Inform system of yesteryear, inform6, as a final stage of compilation, a stage largely invisible to end users of the Inform apps. See structure for a diagram of how the tools are combined in use.

Inform 6 is a C-like language designed to be compiled to the specialist Z-machine or Glulx virtual machines, which in turn were designed for interactive fiction. The Inform 7 repository at Github contains a copy of the most recent stable release of the Inform 6 compiler, but this is only a copy.

The Inform 6 compiler repository is here:

Note that this is a straight-up C program, and not a literate program needing inweb to compile.

§2. The I7 repository does not contain the Inform 6 "Designer's Manual 4th Edition", the "DM4", or the Inform 6 Technical Manual, for which see:

The I7 repository also does not contain the Inform 6 library, which is not used by Inform 7: but see —

§3. However, the I7 repository does contain a version of Andrew Plotkin's test suite for the I6 compiler:

ported to use intest rather than the Python script originally supplied. So if you've already built the Inform 7 tool chain, and are already using intest to test inform7 and the others, then you can run this suite against the included copy of the I6 compiler as well.