AT89C52 to control the use of the core to achieve the realization of the seven

代码说明：

采用AT89C52为控制核心，实现了实现了7位数范围内的数学运算，整数、小数和负数皆可，并可以计算函数。还具有时钟日历和密码功能。-AT89C52 to control the use of the core to achieve the realization of the seven-digit within the scope of mathematics, integer, decimal and negative Jie Ke, and can calculate the function. Also has a clock calendar and password functionality.