§1. Inter is Stages 6 and 7 of the core Inform compiler, but can also be run as a stand-alone tool. See structure for the bigger picture: Inter handles only these parts of the compilation flow —

    kit sources
  (in Inform 6 code)
        | INTER
    Inter trees
        . . . . . . . precompiled      Inter tree
                      Inter trees      from inform7
                            \              /
                             \            /  INFORM7 Stage 6 or INTER
                             \|/        \|/
                        single linked Inter tree
                            /       |       \
                           /        |        \   INFORM7 Stage 7 or INTER
                         \|/       \|/       \|/
                 Inform 6 code   C code     index mini-website

Used as a stand-alone tool at the command line, however, Inter is more flexible and interesting. See the Manual (in inter) and Reference Card (in inter).

§2. The bytecode module provides a low-level API for creating Inter code in memory, including definitions of every Inter construct, together with reading and writing Inter to either binary or text files. This is also where references between one tree and another ("plugs" and "sockets") are managed, and where "transmigration", moving code from one Inter tree to another, is done.

§3. The building module sits on top of bytecode and provides much more powerful facilities for constructing Inter in memory: in particular allowing for out-of-sequence construction which follows hierarchical location maps made in advance. The central stages of the Inform 7 compiler generate Inter using the building API, and not by calling bytecode directly.

building also contains what amounts to a pocket-sized Inform 6 compiler of its own. It can read code in the Inform 6 programming language's syntax and turn that into an inter_schema — in effect, an AST for Inform 6, which is a language so different from Inform 7 that they cannot sensibly have the same AST format. But they can indeed share Inter as an intermediate representation or IR, and they do. building contains the code which converts inter_schema trees to Inter, a process called "assimilation", and this is the main step in building a kit like BasicInformKit from its source.

§4. The pipeline module provides a flexible processing pipeline for performing transformations on trees of Inter code. Steps in such pipelines may include linking trees together, or transmigrating material between them, or performing peephole optimisation, and so on. The design here is intended to make it easy for people to tinker, and to add new, experimental processing steps as Inform develops.

§5. The final module provides for what is usually the final step of a pipeline: the last step of code-generation, when the final output of Inform is written to some text file. For example, it might output a C or Inform 6 program. final is designed to allow for new output formats to be added as Inform develops; in particular it contains a "vanilla" algorithm for code-generating Inter trees to vaguely C-like, procedural languages, and this is used both for C and for Inform 6.

§6. The index module generates the mini-website called the Index for an Inform 7 project, familiar to all users of the Inform app. Note that this is done from the Inter tree alone; all information about the program which is needed to draw up the Index is present in the Inter tree in the form of metadata constants.

§7. Inter also contains the basic foundation library and some services modules: specifically, words, html and arch.