Ncalc - Graphing Calculator 84 is a free education and reference app for iPhone developed by Tran Duy. The app provides an interface similar to the real graphing calculator 84 and offers a range of features. The app has a graphing calculator that supports function, polar, and parametric graphs. Users can press MODE and select the graph mode, and then press Y= to open the graph editor. Pressing GRAPH will draw the functions. The app has interactive and manual tracing modes, and it shows intersections, roots, and extrema (local maximum, local minimum) of function graphs. It also shows the derivative of function graphs and the tangent of function and polar graphs. The app has a best fit line of a set of points, generates a table of value of selected graphs, and calculates min, max, d/dx, integral of selected graphs. In addition, the app has a scientific calculator, equation solver, statistics, and inferential statistics and distributions. The app offers a premium version with advanced math functions, statistics, inferential statistics and distributions, and other features. Subscription payments will be charged to the user's iTunes account at confirmation of purchase and upon commencement of each renewal term. Users can cancel the subscription anytime by canceling it through their iTunes account settings.