Technically speaking almost any tool with moving parts is a machine, but within IF there is a strong trope of Machines with a capital M; Devices more akin to Babbage's difference engine, Enlightenment automata or Colossus than to a bicycle, a can-opener or a robot.
The fondness for machines can partly be attributed to their functional nature - both in the sense that they are useful to players and authors alike, and in the sense that they tend to work very much like a mathematical function, which (unlike more generalised tools) has a single function which it performs predictably - which is not to say that that function cannot be applied in novel ways. But just as significant is the fact that they can be thought of as symbolic microcosms of IF programs: the player fiddles with a bunch of controls on a static artefact, in order to determine an output in complex, unexpected non-static ways.
- Almost invariably will be a large, fixed object.
- Features a wide variety of controls: handles, cranks, buttons, dials, and switches.
- Usually involve mysterious, complicated and unseen inner workings, which may be magical in nature.
- Often has definite inputs (control settings, portable objects fed into it) and outputs (any world change, but often including modified versions of inputted items, new items, opened doors, information).
- Max Blaster and Doris de Lightning Against the Parrot Creatures of Venus (Dan Shiovitz and Emily Short; 2003; TADS 3).
- Metamorphoses (Emily Short; 2000; Z-code).
- Zork (Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling; publisher: Infocom; 1980).
Many IF games play on the theme of the machine without necessarily containing instances of the classic medium-sized functional Device. Interesting examples of this include:
- Bad Machine (Dan Shiovitz; 1998; TADS) is set within a gigantic factory with a hive-mind or central intelligence.
- Slouching Towards Bedlam (Daniel Ravipinto and Star Foster; 2003; Z-code) features a Device-like robot, Triage. Normally robots behave more like NPCs than machines. The game features numerous other examples of machines.