Although overall the software looks useful, there are bugs in it. For instance in the numeric column, you can only use the numeric keypad to enter a decimal point (not the normal full stop, as many users would do). Rustemsoft's support email, was sent immediately to reply to my bug report saying the following: "We are sorry. This is not the software issue. The problem is related to your keyboard configuration. Probably it affected by your regional settings but it is not for sure." Based on the fact that every other application works perfectly without problem, including the standard calculator, you can make your own judgement as to the validity of their statement.