CalQPlus is an excellent programmable calculator. It supports all the basic scientific functions, matrix functions, user-defined functions and graphs. Many functions can be downloaded from the author's website. These extend the power of the calculator considerably. User-defined functions and variables can be conviniently saved to Dropbox and transferred to other devices, if required. Unlike many other calculator apps on the market, the author has thought of, and incorporated, all the features in a programmable calculator that a user would want. There is also an extensive "help" file that many users will appreciated. The special keyboard provided takes a while to get used to, but once this is done, is easy to use and has all the keys required without shifting to a numeric layout. Highly recommended.