说明：  计算器程序，对于加法和减法可以输入任意多位，对于乘法和除法只能处理4为十进制，除法保留了8位小数。按‘c’可以重新输入，按‘q’退出
(calculators procedures for addition and subtraction can be imported arbitrary number, For multiplication and division can handle only four to decimal, the division retains the eight decimal. By the 'c' can be re-imported by 'q' withdrawal)