“A Schizophrenic System Plot Package” by Wright

  • ©Thomas (Tom) J. Wright




    A Schizophrenic System Plot Package

Session/Category Title: Device Independent Graphics Session




    A system plot package is a set of routines that forms plotter machine instructions. Here, system plot routines are assumed to form instructions for relatively low-level plotting tasks such as drawing a line or, at most, drawing an annotated axis, while graphics utility routines are used to perform higher level tasks, such as drawing a contour map, through the use of the lower level routines. System plot packages have certain desirable attributes which are often conflicting or even mutually exclusive. For example, at NCAR almost all plotting is done on a CDC DD80, suggesting that the plot package should be designed to produce instructions for that particular plotter, but the occasional use of other plotters makes device independence essential.

    The “schizophrenic” system plot package described here attempts to be all things to all users (multiple personalities). Because it is implemented through the use of a preprocessor, each user can create a system plot package tailored to the needs of a particular problem. The programmer of the master plot package can make changes to fix errors or add new features, and the users can easily recreate their plot packages to take advantage of the new master package. Implementation of the system is described. Also, since device independence is an area of much interest at this time, this aspect of the system is described in detail.


    1. Wright, T., “Utility Plotting Programs at NCAR,” Atmospheric Technology, Vol. 1, No. 3 (Sep. 1973), pp. 51–57.
    2. Hirschsohn, I., “AMESPLOT – A Higher Level Data Plotting Software System.” Comm ACM, Vol. 15, No. 9 (Sep 1972), pp. 546–555.
    3. “NCAR Scientific Subroutine Library”, Chapter 12.

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