计算器功能比较简单，界面比较清爽，能进行十进制的加、减、乘、除、求倒数和负数功能，后来加上能实现“sin” “cos” “tan” “pow” 功能，clear表示初始化。-Simple calculator functions, interface cleaner, can be decimal add, subtract, multiply, divide, find the inverse and negative features, was added to achieve " sin"　" cos"　" tan"　" pow"　function, clear that the early initialize.