Plankalkül

This chapter describes the first implementation of Plankalkül, the programming symbolism invented by Konrad Zuse in 1945. Plankalkül is both a high-level imperative programming language and a logic specification notation. In Plankalkül, programs can define functions that can be called non-recursively in other programs. There are no preliminary variable declarations: the type of a variable is specified when it is used. The main imperative constructs are: variable assignment, arithmetic and logic operations, guarded commands, and While loops. Plankalkül is also declarative: some special list, set-theoretic, and logic functions are part of the language definition. Plankalkül uses a two-dimensional layout that defies traditional parsers. This and some inconsistencies in the original definition were the main obstacles to its implementation.