Realize the main stack are some of the basic operations, such as: out of stack,...

代码说明：

主要是实现堆栈的一些基本操作，比如：出栈，清空堆栈，访问堆栈顶元素，以及测试堆栈状态等。-Realize the main stack are some of the basic operations, such as: out of stack, empty the stack, the stack top element of the visit, as well as the test stack status.