实现计算器的基本功能。使之能实现基本的加、减、乘、除、开方、倒数等基本运算，同时具有存储数据的功能，能存储相关数据便于下步运算。-To achieve the basic functions of the calculator. So that it can achieve the basic addition, subtraction, multiplication, division, square root, reciprocal and other basic operations, but also has the function of storing data, can store relevant data to facilitate the next step operation.