Rosetta Smalltalk: a conversational, extensible microcomputer language

Rosetta Smalltalk is a personal information handling environment for low-cost microcomputers based on the work of the Learning Research Group at Xerox PARC. Our prototype runs on two different Z-80 based personal computers. The major goals of the system are to support a lively interactive style of working and to provide an open-ended medium in which personalized tools may easily be constructed. Rather than write monolithic programs, the user extends the language with new objects and syntax. He then solves his problems by interacting with his extensions at the keyboard. Multiple independent CRT windows permit several partially completed interactions to be displayed at once.All facilities in Rosetta Smalltalk are represented by objects, which are instances of Simulalike classes. Objects are not operated on directly, but are sent messages requesting them to perform actions and return replies. The language is extended by creating new classes and by adding new messages to existing classes.