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| Plankalkül | |
|---|---|
| Name | Plankalkül |
| Designer | Konrad Zuse |
| Developed | 1943–1945 |
| Paradigm | imperative, algorithmic, data structure oriented |
| Typing | strong (schemata) |
| Influenced by | Zuse's own mechanical computers |
| Influenced | ALGOL, FORTRAN, Pascal, C, Ada, ALGOL 68, ML, Haskell |
Plankalkül is an early high-level programming language designed by Konrad Zuse in the 1940s for expressing algorithms for electromechanical computing devices. Conceived during World War II, it anticipated many structures later seen in ALGOL, Fortran, Pascal, C and Ada by introducing typed schemata, structured data, and formal notation for conditionals and loops. Zuse's work remained largely unpublished during its inception, delaying recognition until researchers associated with Deutsche Forschungsgemeinschaft, Technische Universität Berlin, and Zuse KG re-examined his manuscripts.
Konrad Zuse developed Plankalkül while working on the Z3 and the Z4 computer at Bautzen, Berlin, and later at Hünfeld under wartime constraints. Zuse corresponded with figures and institutions such as Heinrich Hertz, Deutsche Versuchsanstalt, and engineers from Siemens and Telefunken. His manuscripts circulated among technicians, Max Planck Institute scholars, and later historians like Friedrich L. Bauer and Hermann Goldstine, prompting investigation at Technische Universität München and Institut für Informatik. Interest by Hans-Joachim Sperling and Niklaus Wirth contributed to archival work at ETH Zurich and Technische Universität Berlin. Postwar reconstruction and contacts with IBM and British Tabulating Machine Company engineers influenced the reception and eventual publication through Springer-Verlag and MIT Press channels.
Plankalkül introduced typed schemata supporting arrays, records, and nested structures comparable to ALGOL 60 arrays, Pascal records, LISP lists, and Ada packages. Zuse defined operations on Boolean, integer, fixed-point, and floating representations akin to later standards like IEEE 754 and designs in FORTRAN 77. The language provided conditional constructs with semantics reminiscent of ALGOL 68 and looping mechanisms comparable to COBOL and BASIC. Data abstraction ideas foreshadowed concepts in Simula, Smalltalk, Modula-2, and ML. Error handling and assertions paralleled later practices in Dijkstra's work and in Hoare logic formulations.
Plankalkül's notation used explicit variable indexing, hierarchical naming conventions, and formal assignment semantics similar to Backus–Naur form influences seen in ALGOL W and BNF-based grammars. Zuse specified flow control with guarded commands anticipating Dijkstra and Tony Hoare's theories, and provided algebraic notation akin to Turing machines' formal descriptions and Von Neumann architecture discussions. Semantics addressed evaluation order, side effects, and referential transparency issues later studied by John McCarthy and researchers at Bell Labs, IBM Research, and PARC. The language distinguished between value and reference parameters in a manner later formalized in Milner's type systems and Reynolds's work on parameter passing.
No production compiler existed in Zuse's era; later implementations were undertaken by researchers at Technische Universität Berlin, Zuse Institute Berlin, Humboldt University of Berlin, and independent projects at ETH Zurich and University of Oslo. Implementations were studied alongside compilers for ALGOL, Fortran, Cobol, and Algol 68 at institutions such as IBM, Bell Labs, Oxford University Computing Laboratory, and Massachusetts Institute of Technology. Compiler techniques borrowed from Aho, Sethi, Ullman traditions and optimizations akin to those in GCC and LLVM frameworks. Emulation efforts intersected with hardware reconstructions of the Z3, Z4, and modern FPGA recreations by teams at Fraunhofer Society and German Museum of Technology.
Although not widely known immediately, Plankalkül influenced postwar computing thought and was cited by historians such as Friedrich L. Bauer and Gerhard Kowalewski. Its ideas resonate with constructs in ALGOL, Fortran, Pascal, C, Ada, Simula, ML, Haskell, Erlang, Lisp, Prolog, Smalltalk, Modula-2, ALGOL 68, PL/I, BCPL, B and later languages explored at ACM conferences and in journals published by IEEE Computer Society. Zuse's role has been commemorated by institutions such as Deutsches Museum, Zuse Forum, IEEE Computer Society, and German Informatics Society. Awards like Konrad Zuse Medal and exhibitions at Bundesarchiv and National Museum of Computing reflect renewed scholarly interest from Stanford University, Harvard University, University of Cambridge, Oxford University, and University of California, Berkeley researchers.
Surviving manuscripts show algorithms for matrix inversion, chessboard evaluation, and flow-control routines comparable to later examples found in Knuth's works and Sedgewick texts. Sample programs resemble pseudocode used in ALGOL 60 papers and in Fortran IV tutorials from IBM. Demonstrations reconstructed by scholars at Technische Universität Dresden, MPI-SWS, California Institute of Technology, University of Manchester, and Princeton University illustrate arithmetic, boolean logic, and record manipulation akin to exercises in The Art of Computer Programming and Structure and Interpretation of Computer Programs.
Critics note that Plankalkül's notation was dense and idiosyncratic compared with later standardized syntaxes like BNF and ALGOL 60's block structure, drawing critique in analyses by Dijkstra, Hoare, Friedrich L. Bauer, and Niklaus Wirth. Wartime isolation limited peer review by contemporaries at Cambridge University, University of Pennsylvania, Massachusetts Institute of Technology, and Bell Labs, which constrained early adoption relative to Fortran and COBOL. Hardware limitations of Z3 and Z4 machines made practical deployment difficult compared with postwar systems from IBM and UNIVAC. Subsequent scholarship at University of Hamburg, Leipzig University, and University of Bonn has clarified scope, but debates continue among historians at Max Planck Society and curators at Deutsches Technikmuseum.