Smalltalk

Smalltalk is an object-oriented, dynamically typed, reflective programming language created in the 1970s by Alan Kay, Dan Ingalls, and Adele Goldberg at Xerox PARC to investigate constructionist learning of programming in young people.

At one time in the 1990s, Smalltalk reached its peak to become the most popular object-oriented language in the world after C++. See Introduction to the Smalltalk Programming Language.

Smalltalk is a general-purpose programming language, so it is actually used in many, many different problem domains, ranging from embedded applications in small devices to the web, the desktop, mobile, machine learning, natural language processing, financial industry, manufacturing industry, military application, etc.