1．用堆分配存储表示实现Hstring 串类型的最小操作子集。

2．实现串抽象类型的其余基本操作（如联接、删除等），且不能使用c语言本身提供的串函数，必须自己构造新的函数实现串的基本操作。

3．本演示系统是一个命令解释程序，循环往复的处理用户输入的每一条命令，直至终止程序的命令为止。

4．参数的合法性必须严格检查，要严格按照命令的输入格式进行输入，否则程序可能无法正确执行指令。

-1. Heap allocated storage, said with a string type to achieve the minimum operating Hstring subset. 2. The rest of the abstract string type to achieve the basic operations (such as join, delete, etc.), and the language itself can not use the c string function, you must construct a new function to achieve their own string of basic operations. 3. This demo system is a command interpreter, the cycle of processing user input each command, the command up until the termination of the program. 4. Parameters of legitimacy must be strictly inspected in strict accordance with command input format for input, otherwise the program may not correctly execute instructions.