求教数据结构简单的二叉树问题
最近自学数据结构学到二叉树这里，自己敲了一段二叉树的建立和输出，可是不能成功。。想请问是什么问题呢？

#include <stdio.h>
#include <malloc.h>

typedef struct Binary_Node
{
    char data;
    struct Binary_Node *pLchild;
    struct Binary_Node *pRchild;
}BNode;

BNode *create_tree()
{
    char val;
    BNode *BT;
    scanf("%c",&val);
    if(val = ' ')
    {
        BT = NULL;
    }
    else
    {
        BT = (BNode*)malloc(sizeof(BNode));
        BT->data = val;
        BT->pLchild = create_tree();
        BT->pRchild = create_tree();
    }
    return BT;
}

void PreTraverse(BNode *BT)
{
    if(BT)
    {
        printf("%c ",BT->data);
        PreTraverse(BT->pLchild);
        PreTraverse(BT->pRchild);
    }
}

int main(void)
{
    BNode *BT;
    BT = create_tree();
    PreTraverse(BT);

    return 0;
}

数据结构
[解决办法]
BNode *create_tree()
{
char val;
BNode *BT;
scanf("%c",&val);
if(val == ' ') //这里应该是比较 符号 ==
{
BT = NULL;

}
else
{
BT = (BNode*)malloc(sizeof(BNode));
BT->data = val;
BT->pLchild = create_tree();
BT->pRchild = create_tree();
}
return BT;
}