从键盘输入一个字符串，将其中的小写字母全部转换成大写字母，

然后输出到一个磁盘文件"test.dat"中保存，再从该文件中读出

字符串并显示出来。输入的字符串以"！"结束-Keyboard input from a string, lowercase letters, which are all converted to upper case, and then output to a disk file　test.dat　saved, and then from the document read out the string and displayed. Enter the string of　!　End