Very interesting and a bit unusual for a non-standard calculator. There is no digital and functional keys, all values you have to enter manually from the keyboard on the computer in a special field for entering formulas. After you enter all the necessary data, you need to press Enter. After that, you will immediately see a detailed description of all actions, what each action in a new line. With it you can continue to do calculations in any of the lines. The app needs to get used to and prilovchitsya, but its worth it.