The ABC structure editor -- Structure-based editing for the ABC programming environment.
Lambert Meertens, Steven Pemberton, Guido van Rossum · Centrum Wiskunde & Informatica (CWI), the national research institute for mathematics and computer science in the Netherlands · 1992
ABC is an interactive programming language where both ease of learning and ease of use stood high amongst its principle design aims.The language is embedded in a dedicated environment that includes a structure-based editor.To fit in with the design aims, the editor had to be easy to learn, demanding a small command set, and easy to use, demanding a powerful command set and strong support for the user in composing programs, without enforcing a computerscience understanding of issues of syntax and the like.Some novel design rules have led to an interesting editor, where the user may enter and edit text either structurally or non-structurally, without having to use different "modes".