diff --git a/week3/stack.h b/week3/stack.h
index 2f8bf9f..244cc5e 100644
--- a/week3/stack.h
+++ b/week3/stack.h
@@ -1,23 +1,42 @@
+/*
+ * Author: Walter
+ * Student ID: 1930006025
+ * Week_3
+ * Stack
+ */
+
 #include <stdbool.h>
 
+/* struct for stack */
 typedef struct Stack_str {
+	/* the size of stack */
 	int size;
+	/* top index, empty is -1 */
 	int top;
+	/* data */
 	double *data;
 } Stack;
 
+/* create an stack with size */
 bool CreateStack(Stack *stack, int size);
 
+/* check a stack whether it contains data */
 bool IsEmpty(Stack *stack);
 
+/* check full of stack */
 bool IsFull(Stack *stack);
 
+/* get the top value of a stack */
 bool Top(Stack *stack, double *x);
 
+/* add a value to stack */
 bool Push(Stack *stack, double x);
 
+/* delete a value from stack */
 bool Pop(Stack *stack, double *x);
 
+/* print the stack */
 void DisplayStack(Stack *stack);
 
+/* delete a stack */
 void DestroyStack(Stack *stack);