利用函数getchar(), ungetc(), fprintf()来实现基于流的字符输入输出， 即读入键盘输入的数据，从中挑选出字符和数字组成的字符串或整数。-Using the function getchar (), ungetc (), fprintf () to achieve flow-based character input and output, that is read into the keyboard input of data, pick out a string of