从键盘输入一串字符串（显示提示）到内存中，在该字符串的某一个指定位置，插入某 一字符或删除某一字符，并显示操作后的字符串。-Enter a bunch of string from the keyboard (prompts) into memory, in one of the string specified location, insert a character or delete a character, and the string after the operation dis