diff --git a/_04.树/_b.二叉树链式结构.c b/_04.树/_b.二叉树链式结构.c
index 8888c9e..12991c0 100644
--- a/_04.树/_b.二叉树链式结构.c
+++ b/_04.树/_b.二叉树链式结构.c
@@ -2,12 +2,12 @@
  * @Author: Xu Bai
  * @Date: 2019-07-13 22:24:04
  * @LastEditors: Xu Bai
- * @LastEditTime: 2019-07-19 22:49:14
+ * @LastEditTime: 2019-07-23 22:51:03
  */
 #include "string.h"
 #include "stdio.h"
 #include "stdlib.h"
-#include "io.h"
+//#include "io.h"
 
 #define OK 1
 #define ERROR 0
@@ -44,7 +44,7 @@ Status StrAssign(String T, char *chars)
 
 typedef char ElemType;
 /*�ַ����Կո�Ϊ�� */
-ElemType Nil = ' ';
+ElemType Nil = '#';
 
 Status visit(ElemType e)
 {
diff --git a/_04.树/_c.线索二叉树.c b/_04.树/_c.线索二叉树.c
new file mode 100644
index 0000000..93f0b6d
--- /dev/null
+++ b/_04.树/_c.线索二叉树.c
@@ -0,0 +1,41 @@
+/*
+ * @Author: Xu Bai
+ * @Date: 2019-07-23 22:43:14
+ * @LastEditors: Xu Bai
+ * @LastEditTime: 2019-07-23 22:52:27
+ */
+#include "string.h"
+#include "stdio.h"
+#include "stdlib.h"
+#include "io.h"
+
+#define OK 1
+#define ERROR 0
+#define TRUE 1
+#define FALSE 0
+#define MAXSIZE 100
+
+typedef int Status;
+typedef char ElemType;
+/*Link==0��ʾָ�����Һ���ָ�룬Thread==��ʾ���� */
+typedef enum
+{
+    Link,
+    Thread
+} PointerTag;
+
+typedef struct BiThrNode
+{
+    ElemType data;
+    struct BiThrNode *lchild, *rchild;
+    PointerTag LTag;
+    PointerTag RTag;
+} BiThrNode, *BiThrTree;
+
+ElemType Nil = '#';
+
+Status visit(ElemType e)
+{
+    printf("%c ", e);
+    return OK;
+}
\ No newline at end of file