Active Text for Structuring and Understanding Source Code

Programs are not read sequentially like a book but rather selectively like an encyclopedia. Instead of linear text we therefore suggest non-linear active text as a medium for structuring and browsing source code. While common program editors are mainly character based we believe that non-textual information such as pictures, links, folds, and annotations can improve the readability of programs. In this paper we show how a text editor can be extended to include active text elements and give examples for how to apply these facilities to source code. The implementation was done in the Oberon system which offers powerful mechanisms for extending software in an object-oriented way.