说明：  通过调用ＢＴＯＦ子程序，将各变量转换成二进制浮点操作数，再进行各 种运算，最后调用ＦＴＯＢ子程序，还原成十进制形式，供输出使用。
(BTOF by calling the subroutine, the variable will be converted into a binary floating-point operand, and then conduct various kinds of computation, the final call FTOB subroutine, to restore the form of the metric system for output use.)