The Io programming language

Io is a pure object-oriented programming language inspired by Smalltalk, Self, Lua, Lisp, Act1, and NewtonScript. Io has a prototype-based object model similar to the ones in Self and NewtonScript, eliminating the distinction between instance and class. Like Smalltalk, everything is an object and it uses dynamic typing. Like Lisp, programs are just data trees. Io uses actors for concurrency, a technique rarely used in modern programming languages. Remarkable features of Io are its minimal size and openness to using external code resources. Io is executed by a small, portable virtual machine.