MINICOMPUTE~ SOFTWARE DEVELOPMF~IT USING A MAXICOMPUTER M. W. Blake-Enox C. C. Morris Bell-Northern Research Ottawa, Canada INTERPRETIVE EXECUTION OF REAL-TIME CONTROL APPLICATIONS Mary S. Adix Henrik A. Schutz General Motors Research Laboratories Abstract This paper examines some of the problems of developing software for minicomputers (or microcomputers). Practical solutions to these problems, involving the use of maxicomputers, are described both generally and by a specific example. Areas examined include source program input and editing, compilation and assembly, loadi~igand finally debugging. In addition, performance measurement of application software is discussed. Abstract Interpretive execution has often been regarded as too slow for real-time control applications. Assembly language implementations, however, may exhaust available memory long before running out of machine cycles. For such applications, interpretation of a virtual machine language (VML) is attractive if it yields substantial memory savings at a tolerable cost in execution time. This paper discusses the design of a VML and interpreter which have been used to implement a real-time control application. Performance is evaluated relative to an assembly language version of the same problem. The assembly language version executed 4.8 times faster than the interpretive version, but required 51% more memory. Space compaction is achieved by making basic operations in the application area primatives of the VML. The interpreter simulates a computer whose machine language is the VML. In addition to conserving memory, this approach can facilitate the implementation of a high-level programming language on a variety of minicomputers. ?~0GRAM CONTROL VIA TRANSITION MATRICES-A NOVEL iPPLICATION OF MICRO-PROGRAMMINC S. finn Oliver, Nell D. Jones University of Kansas Abstract The problem of processing and interpreting character-strings in a systematic, efficiently implementable manner has given rise to a variety of decision- (or transition-) table and transition-diagram techniques. These have been used in the d e s i g n ~ d / o r coding of string~ oriented processors, such as lexical analysis portions of compilers. All these techniques share in common the idea of an input driven transition control. This report describes a micro-coded implementation of a particularly rich concept -the transition matrix (TM). The micro-coded interpreter (ITM) executes the flow-of-control implicit within the structure of the TM. The TM may be coded 121 a natural, easy to use language (LTM~SP), ~nd then be automatically translated into ITN-usable form by a user-level translator called TM~SP. The completed system (ITM and TM~SP) permits TM-oriented decisionmakimg techniques %o be utilized in virtually any task that can be described by means of a transition matrix. STRUCTURING BASIC PROGRAMS FOR MANAGING O VI~LAYS IN A SMALL COMPUTER SYSTEM Ted Cary Computer Science Program Wichita State University Wichita, Kansas Abstract In a small computer system, it is not unusual to write a BASIC program which is too large to fit into main memory. Such a program must be replaced by a collection of overlay modules together with inter-module sequencing logic. A sophisticated BASIC interpreter allows this sequencing to be done under program control. Unless carefully managed, a decomposition can produce an environment where programs exhibit undesirable characteristics. A structuring and -7-

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