Inform

Inform refers a family of programming languages intended for interactive fiction games and the related software for writing and compiling them.

Inform 6 is a fairly traditional programming language which is compiled into bytecode for the "Z-machine". Inform 7 is a higher level programming language which is largely similar to written English, making the code usually easy to read. The Inform 7 compiler converts such code into Inform 6 code. As of 2021, the planned release of Inform as Free Software has not yet happened. There are however games written in Inform, which are fully Free. Games can be played with a fully free zcode interpreter such as Frotz.