命令解释程序的编写

编写类似于DOS，UNIX的命令行解释程序

（1）自行定义系统提示符

（2）自定义命令集（8-10个）

（3）用户输入HELP以查找命令的帮助

（4）列出命令的功能，区分内部还是外部命令

（5）用户输入QUIT退出

（6）内部命令有dir, cd, md, rd, cls, date, time, ren, copy等。-Command interpreter program similar to the DOS, UNIX command line interpreter (1) of preparing the custom command set their own definition of the system prompt (2) (8-10) (3) user input HELP to find the command help (4 ) lists the function of the command, the distinction between internal or external command (5) user input QUIT exit (6) internal commands dir, cd, md, rd, cls, date, time, ren, copy, etc..