The programming language created at Xerox PARC in the 1970s that pioneered object-oriented programming with a graphical user interface is Smalltalk.
Smalltalk was developed by Alan Kay, Dan Ingalls, Adele Goldberg, and others at Xerox PARC. The project grew from Kay's idea of a personal computer for children and from earlier work on the Dynabook concept. Smalltalk systems combined the programming language, development tools, and user interface into an interactive environment.
Its design treated nearly everything as an object, including numbers, classes, and graphical interface elements. The system used windows, icons, menus, and a mouse-driven interface before those features became common in consumer computers.
Smalltalk influenced later languages and software environments, including Objective-C, Ruby, Java, and modern integrated development environments. It is not the first object-oriented language—that distinction is generally associated with Simula—but it was one of the most influential pure object-oriented languages.