The Programming Language Oberon-2

Oberon–2 is a general–purpose language in the tradition of Oberon and Modula–2. Its most important features are block structure, modularity, separate compilation, static typing with strong type checking (also across module boundaries), and type extension with type–bound procedures. Type extension makes Oberon–2 an object–oriented language. An object is a variable of an abstract data type consisting of private data (its state) and procedures that operate on this data. Abstract data types are declared as extensible records. Oberon–2 covers most terms of object–oriented languages by the established vocabulary of imperative languages in order to minimize the number of notions for similar concepts. This report is not intended as a programmer’s tutorial. It is intentionally kept concise. Its function is to serve as a reference for programmers, implementors, and manual writers. What remains unsaid is mostly left so intentionally, either because it can be derived from stated rules of the language, or because it would require to commit the definition when a general commitment appears as unwise. Appendix A defines some terms that are used to express the type checking rules of Oberon–2. Where they appear in the text, they are written in italics to indicate their special meaning (e.g. the same type).