顺序栈的基本操作中Push压入后的- S.top = S.base + S.stacksize; 作用

#include <stdio.h>
#include <malloc.h>
#define TRUE 1
#define OK 1
#define ERROR 0
#define FALSE 0
#define STACK_INIT_SIZE 100
#define STACKINCREMENT 10

typedef int Status;
typedef int SElemType;

struct SqStack
{
    SElemType *base;
    SElemType *top;