Smalltalk
From Just Solve the File Format Problem
Smalltalk, a programming language introduced in the early 1970s for educational use at Xerox PARC, introduced some concepts which are common in modern programming languages, particularly object-oriented structure. It also uses dynamic typing for variables, something done by some modern languages (while others prefer the opposite approach of strong typing imposed on variables at compile time).
There are a number of different versions of Smalltalk, some named based on the year they were introduced (Smalltalk-72, Smalltalk-76, Smalltalk-80). Most versions in use now are derived from Smalltalk-80.
