...the speed of light, which is not possible. Incase we do that will it convert into light? No, because the mechanisms are different. Anyway, your question is a bit like asking: "if the Moon is made of green cheese, what keeps it fresh"? You can ask all kinds of questions about impossible or nonexistent situations, but they still have no meaning. R.G. Vickson Bye Sanny

....com/. And yes if the stepsize goes to 0, and rounding errors are not a problem, But, rounding errors are always a problem, at least in floating-point arithmetic. That's why the step-size choice problem is nontrivial. R.G. Vickson the error should get better if you don't have other mistakes. Halving the stepsize may not have been nearly a large enough reduction. Fred

...: if it is too large, truncation errors are excessive, but if it is too small, roundoff errors ruin everything. If you want really small step-sizes, you may need to go with extended-precision arithmetic. Most numerical analysis books or books about the numerical solution of DEs will contain discussions of stepsize choice. Good luck. R.G. Vickson Kind Regards, Matt