Interactive Computer Program System for Integration of Multistep Reaction Rate Equations We have elsewhere described' the HAVCHM program system for integration of the rate equations resulting from a set of elementaw reactions. rate constants. and initial concentrations. to eive the concentration versus time for each s ~ e c i e s in the (.emti& scheme. a he Gear inteelation method is emoloved: wiihout use of the auasi-steadv-state annroxim~ation. in an atmospheric photochemistry simulation which has been previously described hem2 However, this system was designed far card input batch computation. We are writing to report that we have recently modified the system for use with a n interactive minicomputer system, using an appropriately simplified and annotated input data structure, and a subroutine has been added to permit the use of a plotting display of the concentration versus time output selected species. This greatly simplifies and facilitates the educational use of the HAVCHM system if a minicomputer system is available for operation with Fortran IV. Specifically, the Fortran IVprograms were modified for use with a DEC 11-03minicomputer system having 56K bytes (28K 16 hit words) of available core, RXOl floppy disc drives, and a VT55 video terminal with plotting capability. With dimensioning for 100 reactions and up to 20 different chemical species, the complete program system and operating routines require 42.1K bytes (21K words) of core memory if an overlay structure is used, or 54.3K bytes (27.2K wards) if no overlay structure is used. Although the plotting subroutine selects and s c a k the output data for plotting of up to two species at a time using the PLOT55 commands for the DEC VT55 terminal, the data arrays could readily be used by other plotting systems, or the graphical output routine removed if only numerical output is possible. The program system is available as a set of FORTRAN IV program files copied by the DEC RT-11 operating system on a single sided floppy disc. To ohtain this program disc send $12 to cover costs for a non-returnable disc and documentation to John P. Chesick. 'Stabler, R. N., and Chesick, J. P., Intl. J. Chem. Kinet., 10,461 (1978). %Stabler,R. N., and Chesick, J. P., J. CHEM. EDUC., 55,504 (1978).
Haverford College Haverford, PA 19041
J o h n P. Chesick
Volume 56, Number 9, September 1979 / 585
