PCDP(ID:5580/pcd001)


Macro-assembler with symbolic capabilities


References:
  • Bork, Alfred "PCDP;" University of California, Irvine. view details
  • Farber, David J. "A survey of the systematic use of macros in systems building" view details Extract: Survey
    In the field of generating computer dialogues designed for instructional use, a number of specialized languages have been developed (Coursewriter, Planit, Foil). While the use of such languages has numerous advantages, they do impose limitations on the use of the machine proper. In addition, the language may not be available on more than one machine. An alternative to using these specialized languages is to use standard languages such as PL/I, SNOBOL, etc. A third and uncommon alternative is to use an extended machine language--namely, a macro system. PCDP is based on the use of Sigma 7 Metasymbol.

    I would like to quote from a paper by Professor Alfred M. Bork and Charles Mosmann:

    "These capabilities make a macro-assembler extremely attractive for use in developing a system for producing instructional dialogues. In using it as the basis for our system, we cannot say that we have developed a language for composing conversational programs ; nor have we written a compiler or interpreter of some language. The system described here is simply a flexible set of macro-instructions which, added to the existing capabilities of Metasymbol and the BTM time-sharing monitor on the Sigma-7, allows a teacher considerable flexibility and convenience in writing instructional dialogues. The system is now available and is being used to write instructional dialogues. It should be clear that such a system is never "complete"--one of its major advantages is the ease with which additional features can be added and new terms be defined. The system depends, obviously, on the facilities of Metasymbol and the Sigma-7; but the idea could easily be adapted to any computing system with a macro- assembler of the general type of Metasymbol."

    I would further llke to illustrate with a program from PCDP. This program is simple first grade material and needs no explanation. Abstract: Assemblers with macro capabilities have been available for over ten years. There has been a limited number of mainly unpublished systematic uses of such capabilities in the construction of a variety of systems. This paper will cover a number of these cases. We will examine the features of the macro systems which allowed their usage as well as the method used in the system implementation. We will comment on the effect on efficiency and flexibility that the use of this facility has produced.
          in [ACM] SIGPLAN Notices 6(10) October 1971 Proceedings of the SIGPLAN symposium on Languages for system implementation 1971, Lafayette, Indiana, United States; October, 1971 view details