We present two examples of microworlds built into the Smalltalk environment for the purpose of teaching the main concepts of object oriented programming (OOP) and of the Smalltalk programming language. Thee distinguishing features of our microworlds are that each of them presents the student with a sequence of environments. These environments introduce one OOP concept after another, and disclose the Smalltalk environment and language in a step-by-step fashion. The starting environment does not require any programming and does not encourage the user to use Smalltalk tools, the last environment must be programmed in Smalltalk and discloses the major Smalltalk tools. The intended use of our microworlds is for the introductory part of a course on OOP, to be followed by a detailed presentation of the language. An extension of the presented approach would make the method suitable for teaching basics of computer programming in a computer literacy course.

Microworld, object oriented programming, progressive disclosure, Smalltalk, teaching object oriented programming, computer literacy.