FORSCHUNGSZENTRUM JÜLICH GmbH
Zentralinstitut für Angewandte Mathematik
D-52425 Jülich, Tel. (02461) 61-6402
Informationszentrum, Tel. (02461) 61-6658
Technical Information
FZJ-ZAM-TKI-0305
Thomas Eickermann, Wolfgang Frings,
Anke Häming, Birgit Reuter
14.05.1997
Nassi-Shneiderman diagrams serve to synoptically represent algorithms and program sequences by creating a graph of the elements of structured programming (loops and multi-way decisions) which can give a better overview in the case of complicated algorithms. The representation of algorithms using Nassi-Shneiderman diagrams is rather needed for small-scale programming, where it is a good alternative to flow diagrams.
The nassi program developed at ZAM serves to generate such Nassi-Shneiderman diagrams under Unix. nassi can be used to convert programs and algorithms available in C pseudocode or in C or PASCAL language into a graph. In this first version, nassi only supports a subset of the C programming language. A restriction is that the C parser of nassi does not recognize any definitions of variables within functions and is thus unable to exclude these from the diagram. However, since in most cases the diagrams are used in documentations where C pseudocode should be used, the restriction to the analysis of C pseudocode is not particularly relevant. In generating the graph, each function in the input is converted into a separate diagram.
For representation and postprocessing nassi provides a convenient interface with which single diagrams can be selected, represented, issued in different output formats and printed. The interface permits all menu-variable global options to be stored in profiles or directly in the source.
A graphics editor allows layout changes of the whole diagram or of single statements or control structures. If diagrams are too crowded, statements and whole structures can be hidden or shifted as a block to a separate diagram. Such changes to the layout and structure of diagrams can be stored again in the source code via special comments and are then directly available for further treatment of the source code.
For output purposes, nassi also provides the option of generating source data of the Tgif and Xfig graphics editors in addition to screen output, Encapsulated PostScript graphics and printable PostScript files. This makes it possible to also change and extend diagrams far beyond the functionality of the built-in graphics editor. For the rapid generation of diagrams nassi provides a batch option which generates diagrams in the desired output format independent of the interface.
