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Suggested Citation:"Porting TRIM2 to an MS-DOS Environment." National Research Council. 1991. Improving Information for Social Policy Decisions -- The Uses of Microsimulation Modeling: Volume II, Technical Papers. Washington, DC: The National Academies Press. doi: 10.17226/1853.
Page 221

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FUTURE COMPUTING ENVIRONMENTS FOR MICROSIMULATION MODELING 221 computer technology, the relative costs are favorable, the potential for friendly and effective user interfaces is far greater, and the degree of user control and interaction is compelling. In the longer run, we believe that only desktop environments should be considered for implementation and operation of the types of microanalytic models that are in use today. However, we have some concern about the value of moving TRIM2 as is to a desktop computing environment. Our concern in not due to any doubt about the technical feasibility of making the move. TRIM2 can be ported to either an MS-DOS-based microcomputer environment or a UNIX-based workstation environment, and it could be executed successfully in either. These possibilities are discussed below. Porting TRIM2 to an MS-DOS Environme nt Early MS-DOS environments were limited by processing power, address space, and peripheral storage capacity. These limitations can now all be overcome in reasonably effective ways, providing an environment in which TRIM2 could operate. The Intel 80286 and 80386 processors provide for address spaces of at least 16 MB; the 80386 chip is more powerful and has a muc h larger address space with muc h larger address segments. Third-party extensions to MS- DOS in the form of DOS extenders88 allow programs to operate in large physical memories and even larger virtual memories. An MS-DOS microcomputer environment based on an 80386 processor (such as a Compaq Deskpro 386 system) and a DOS extender (such as PharLap) provides an operating environment comparable in interactive flexibility to many IBM 360/370/4300 systems. Disk capacities of 100–300 MB can now easily be included in such configurations; in addition, options such as 8-mm video tape, WORM (Write Once Read Many) optical drives, CD-ROM drives, and erasable optical media are available with capacities of 100 MB to 2.3 GB (gigabytes) for attachment to MS-DOS-based systems. TRIM2's average object module size of 1.5 MB, its master file size of about 100 MB, and its active file sizes of 20 MB or greater all fit into such an environment with little difficulty. There are several FORTRAN-language translators with 32-bit addressing capability that could compile TRIM2 code into an extended DOS environment; one is distributed by Watcom (Waterloo, Ontario). For maintaining the CTD, comprehensive COBOL-language processors (such as the compiler supplied by Realia, Inc., Chicago, Ill.) support the index sequential data organization used to maintain the CTD. 88 DOS extenders are increasingly being used to execute DOS programs in the increasing amounts of both real and virtual memory that such architectures as those based on Intel 80286 and 80386 chips provide. Two popular DOS extenders are PharLap and DOS/16M (Rational Systems, Inc., Natick, Mass.); they are currently used by Mathematica, P-STAT, Audodesk, Informix, and Viewlogic.

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Improving Information for Social Policy Decisions -- The Uses of Microsimulation Modeling: Volume II, Technical Papers Get This Book
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This volume, second in the series, provides essential background material for policy analysts, researchers, statisticians, and others interested in the application of microsimulation techniques to develop estimates of the costs and population impacts of proposed changes in government policies ranging from welfare to retirement income to health care to taxes.

The material spans data inputs to models, design and computer implementation of models, validation of model outputs, and model documentation.

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