The quickest and easiest way to do scientific or engineering calculations is by using MS Excel, the spreadsheet software. It does have limitations, so Excel occupies a large niche between calculators and Matlab or compiler generated code. Worksheet functions can do some of what NR offers (including matrix inversion), but to get the flexibility needed for most applications, it is necessary to use the VBA (visual basic for applications) macro language. (The book "VBA and Macros...," by Jelen & Syrstad is good; see amazon.com for it and others.) Hint: Use the VBA editor for code, notably loops and block-ifs, and the macro recorder for formatting, graphics, and dynamically inserting worksheet functions. Attached is only a description for the Lorenz "butterfly" Excel file, since the zipped Excel + MSWord > 100KB. For the Excel, send a request to turtle_hollow@sigmaxi.net(NB:turtle_hollow...). The VBA uses Gill's method, which differs very slightly from the Runge-Kutta in NR, and a fixed step size. But it's enough to get you started. ;)