本程序演示for-for的二重循环结构。外层for语句的循环变量是i，控制总共显示多少行 内层for语句 的循环变量是j,控制每行显示多少字符。-demonstration of the procedure for-2 for the cyclic structure. For the outer part of the cycle variables i, control a total number of firms showed statement for the inner circ