Smalltalk is an object-oriented, dynamically typed reflective programming language. Smalltalk was created as the language in underpinning the "new world" of computing exemplified by "human–computer symbiosis".
Smalltalk is an object-oriented programming language with a rich history and a storied legacy. It was born at Xerox PARC in the 1970s, created by the brilliant and visionary team of Alan Kay, Dan Ingalls, and Adele Goldberg. Smalltalk was created to investigate teaching programming to children. Understandably, it's a very small and simple language, the simplest of the major programming languages.... More Info »
Smalltalk is a recursion on the notion of computer itself. Instead of dividing “computer stuff” into things each less strong than the whole?—?like data structures, procedures, and functions which are the usual paraphernalia of programming languages?—?each Smalltalk object is a recursion on the entire possibilities of the computer. Thus its semantics are a bit like having thousands and thousands of computers all hooked together by a very fast network.
And Smalltalk’s contribution is a new design paradigm? for attacking large problems of the professional programmer, and making small ones possible for the novice user. Object-oriented design is a successful attempt to qualitatively improve the efficiency of modeling the ever more complex dynamic systems and user relationships made possible by the silicon explosion.
There are several good Smalltalk dialects, such as Squeak, Pharo, and Dolphin Smalltalk (for Windows).