使用open函数、构造函数、文件流对象的成员函数打开文件，定义一个二维数组，用键盘输入二维数组的元素值，输出二维数组元素值及其最大值。 -Using open function, constructors, file stream object' s member function to open the file, define a two-dimensional array, use the keypad to enter the two-dimensional array element value, the output value of the maximum two-dimensional array element.