学数据结构不久，为何我先序建立二叉树后，不能输出的呢？
#include<iostream>
#include<iomanip>
using namespace std;
#define OVERFLOW 0
#define NULL 0
#define OK 1
typedef int Status;
typedef char ElemType;
typedef struct BiTree
{
ElemType data;
struct BiTree *Lchild;
struct BiTree *Rchild;
}BiTree,*Binary_Tree;
//创建一个二叉树
Status CreateBiTree(Binary_Tree &T)
{
char ch;
   T=(Binary_Tree)malloc(sizeof(BiTree));
   if(!T) exit(OVERFLOW);
   cin>>ch;
   if(ch=='@') T=NULL;
   else
   {
    T->data=ch;
    CreateBiTree(T->Lchild);  
    CreateBiTree(T->Rchild);
   }
return OK;
}
//先遍历二叉树
Status PreShowBiTree(Binary_Tree T)
{
if(T!=NULL)
{
   cout<<T->data<<setw(3);
   PreShowBiTree(T->Lchild);
   PreShowBiTree(T->Rchild);
}
return OK;
}
//中遍历二叉树
Status MidShowBiTree(Binary_Tree T)
{
if(T!=NULL)
{
   MidShowBiTree(T->Lchild);
   cout<<T->data<<setw(3);
   MidShowBiTree(T->Rchild);
}
return OK;
}
//后遍历二叉树
Status BehShowBiTree(Binary_Tree T)
{
if(T!=NULL)
{  
   BehShowBiTree(T->Lchild);
   BehShowBiTree(T->Rchild);
   cout<<T->data<<setw(3);
}
return OK;
}
int main()
{
BiTree *T;
cout<<"请创建一个二叉树: "<<endl;
CreateBiTree(T);
cout<<"先序遍历: ";
PreShowBiTree(T);
cout<<endl;
cout<<"中序遍历: ";
MidShowBiTree(T);
cout<<endl;
cout<<"后序遍历: ";
BehShowBiTree(T);
cout<<endl;
return 0;
}
比如先后输入ABC@@DE@G@@F@@@ 之后按回车，怎么没有反映的呢？        麻烦帮忙解决下，不胜感激！