抓狂！2叉树创建哪错了！

void mian()
{
BiTree aTree;
creat(aTree);

}

typedef struct Bitnode
{
struct Bitnode* lchild;
struct Bitnode* rchild;
Data data;
}*BiTree;

void creat(BiTree &T)
{
char ch;
ch=getchar();
getchar();
if(ch==' ')
T=NULL;
else
{
T=(BiTree)malloc(sizeof(Bittree));
T->data=ch;
creat(T->lchild);
creat(T->rchild);
}
}

void main() // main错写成mian
{
BiTree aTree;
creat(aTree);

}