(41C/CV/CX) Epidemiologic Programs for Computers & Calculators

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An extract from Epidemiologic Programs for Computers and Calculators, SIMPLE ALGORITHMS FOR THE REPRESENTATION OF DETERMINISTIC AND STOCHASTIC VERSIONS OF THE REEDFROST EPIDEMIC MODEL USING A PROGRAMMABLE CALCULATOR, AMERICAN JOURNAL OF EPIDEMIOLOGY, Vol. 123 No. 5, 1986, pages 905-915

   Two programs are described for the emulation of the dynamics of Reed-Frost progressive epidemics in a handheld programmable calculator (HP-41C series). The programs provide a complete record of cases, susceptibles, and immunes at each epidemic period using either the deterministic formulation or the trough analogue of the mechanical model for the stochastic version. Both programs can compute epidemics that include a constant rate of influx or outflux of susceptibles and single or double infectivity time periods. …
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         MATERIALS AND METHODS
                     Equipment
   Programs were written for an HP-41CV programmable calculator (Hewlett-Packard Co., Corvallis, OR). The minimal system configurations enabling execution of the two programs are 1) the basic HP-41C calculator equipped with two HP-82106A memory modules or one HP-82170A Quad memory module, or 2) an HP-41CV or an HP-41CX calculator. Use of the HP-82182A time module enables generation of automatic time-dependent random number seeds. Although this would have represented a desirable feature for the stochastic version, we resorted to a keyboard-entered, user-chosen seed to reset the generator. The programs contain several instructions to allow printing of the output. We used an HP-82143A printer (Hewlett-Packard Co.) to obtain a permanent record of the results, i.e., frequencies of cases, susceptibles, and immunes at each epidemic period and a pictorial representation of the aligned balls in the trough. However, use of a printer is not mandatory since all results, except the trough picture, will be displayed in the calculator also. Unattended program execution is possible only with the printer present in the system. Use of the HP-82104A card reader is optional. …
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         Description of the algorithms
   The two programs, REED and FROST, although totally independent with respect to register usage, flag control, and execution, share the same basic structure. Both programs are divided into two major routines: input and data processing. …
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                                       TABLE 1
Operating instructions for programs REED and FROST in user mode …
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APPENDIX: PROGRAM LISTINGS …
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