链栈的代码解析

    /***链栈的实现***/
    #include <fstream>
    #include <iostream>
    using namespace std;
    
    #define OK 1
    #define ERROR 0
    #define OVERFLOW -2
    typedef int Status;
    typedef char SElemType;
    
    typedef struct StackNode
    {
    SElemType data;
    struct StackNode *next;
    } StackNode, *LinkStack;
    
    //算法1　链栈的初始化(无头节点)
    Status InitStack(LinkStack &S)
    { // 构造一个空栈 S，栈顶指针置空
    S = NULL;
    return OK;
    }
    
    //算法2　链栈的入栈
    Status Push(LinkStack &S, SElemType e)
    { //在栈顶插入元素e
    LinkStack p;
    p = new StackNode; //生成新结点
    p->data = e;