Io is a pure object-oriented programming language inspired by Smalltalk, Self, Lua, Lisp, Act1, and NewtonScript.

[2] Io has a prototype-based object model similar to those in Self and NewtonScript, eliminating the distinction between instance and class.

[4] Io's goal is to explore conceptual unification and dynamic languages, so the tradeoffs tend to favor simplicity and flexibility over performance.

In its simplest form, Io syntax is composed of one identifier:[5] Assuming the above doStuff is a method, it is being called with zero arguments and as a result, explicit parentheses are not required.

The Io parser intercepts a set of operators defined by the interpreter, and translates them to method calls.