Smalltalk was designed by Alan Kay and his Learning Research Group at Xerox PARC, with major contributions from Dan Ingalls, Adele Goldberg, and others. In his firsthand history, “The Early History of Smalltalk,” Kay describes how the language emerged in the early 1970s from a vision of personal computing for everyone, including children.
Where Simula had added objects to a conventional language, Smalltalk made objects the whole story. Everything in the system is an object, and the only way objects interact is by sending messages to one another. Kay later said he regretted coining the term “object-oriented” because the central idea was really messaging, not just objects and classes.
Smalltalk was not only a language but a complete interactive environment. It ran on the Xerox Alto with a bitmapped display, overlapping windows, pop-up menus, and a mouse. This work directly shaped the modern graphical user interface that later reached the public through the Apple Macintosh and beyond.
The language was also a research vehicle that went through several versions, culminating in the widely studied Smalltalk-80. Its ideas about live, malleable systems and pure object messaging continue to influence language and tool design.