You may use this program for c personal, educational or research purposes.
Commercial purposes require c special arrangements.
If you publish a paper that depends upon this code, c please cite it appropriately. This general-purpose c choice can be modified if need be. If stepsize overshoots, decrease it. Input are the dependent c variable y and its derivative dydx at the starting value of the c independent variable x. Also input are the stepsize to be attempted c htry, the required accuracy eps, and the value yscale, against which the c error is scaled.