说明：  no intro
(1, the realization of the interface design: a software frame; 0-9 digital button and the decimal point; addition subtraction multiplication and division, sign, sign, sqrt, is equal to the reciprocal, square root operation symbols; a clear button, and a reset button; 2, the computing range of the real: the most basic addition, subtraction, multiplication and four operations and the positive and negative conversion, reciprocal, square root, percentage of conversion; 3, achieve a function of clearance and reset: click the Back button to achieve data clearance; click the C button to achieve data reset (reset) function.)