diff --git a/labs/07_list_implementation/README.md b/labs/07_list_implementation/README.md
index 2835680..8a229aa 100644
--- a/labs/07_list_implementation/README.md
+++ b/labs/07_list_implementation/README.md
@@ -20,6 +20,20 @@ of the push_front, pop_front, and pop_back functions.
 **To complete this checkpoint**, show a TA the implementation and memory debugger output before and
 after writing destroy_list.
 
+## Checkpoint 2: 
+*estimate: 20-30 minutes*
+
+The PushBack() and the PrintList() function are used in [checkpoint2.cpp](checkpoint2.cpp), but their definitions are missing, please complete these two functions and make sure the program runs and produces the following output.
+
+```console
+$ g++ checkpoint2.cpp
+$ ./a.out
+Linked List of NodeA nodes: 1 -> 2 -> 3 -> 4 -> 5 -> nullptr
+Linked List of NodeB nodes: 1 -> 1.41421 -> 1.73205 -> 2 -> 2.23607 -> nullptr
+```
+
+**Note**: Hardcoding the PrintList() function to do nothing but just print the above two messages is strictly prohibited. Students doing that will be evicted from the lab room.
+
 ## Checkpoint 3: 
 *estimate: TBD*
 
diff --git a/labs/07_list_implementation/checkpoint2.cpp b/labs/07_list_implementation/checkpoint2.cpp
new file mode 100644
index 0000000..e3631d8
--- /dev/null
+++ b/labs/07_list_implementation/checkpoint2.cpp
@@ -0,0 +1,82 @@
+/* This program attempts to create two linked list, one linked list consists of nodes of class NodeA type, 
+ * the other linked list consists of nodes of class NodeB type, but we would like to use the same 
+ * PushBack() function to append nodes to the end of these two linked lists, and use the same PrintList() function
+ * to print the elements in both lists, and thus we need to make the PushBack() and the PrintList() templated functions.
+ */
+
+#include <iostream>
+#include <cmath>
+
+class NodeA {
+public:
+	int data;
+	NodeA* next;
+	NodeA* prev;
+};
+
+class NodeB{
+public:
+	double data;
+	NodeB* next;
+	NodeB* prev;
+};
+
+int main() {
+	// Part 1: test NodeA class.
+	// Initialize an empty linked list, consisting of NodeA nodes.
+	NodeA* headA = nullptr;
+
+	// Create nodes and add them to the end of the list using PushBack
+	for (int i = 1; i <= 5; ++i) {
+		NodeA* newNode = new NodeA;
+		// data of NodeA is an int type.
+		newNode->data = i;
+		newNode->next = nullptr;
+		newNode->prev = nullptr;
+
+		// Add the node to the end of the list
+		PushBack(headA, newNode);
+	}
+
+	// Print the linked list to verify the nodes
+	std::cout << "Linked List of NodeA nodes: ";
+	PrintList(headA);
+
+	// Clean up memory (free nodes)
+	NodeA* currentA = headA;
+	while (currentA != nullptr) {
+		NodeA* next = currentA->next;
+		delete currentA;
+		currentA = next;
+	}
+
+	// Part 2: test NodeB class.
+	// Initialize an empty linked list, consisting of NodeB nodes.
+	NodeB* headB = nullptr;
+
+	// Create nodes and add them to the end of the list using PushBack
+	for (int i = 1; i <= 5; ++i) {
+		NodeB* newNode = new NodeB;
+		// data of NodeA is a double type.
+		newNode->data = (double)sqrt(i);
+		newNode->next = nullptr;
+		newNode->prev = nullptr;
+
+		// Add the node to the end of the list
+		PushBack(headB, newNode);
+	}
+
+	// Print the linked list to verify the nodes
+	std::cout << "Linked List of NodeB nodes: ";
+	PrintList(headB);
+
+	// Clean up memory (free nodes)
+	NodeB* currentB = headB;
+	while (currentB != nullptr) {
+		NodeB* next = currentB->next;
+		delete currentB;
+		currentB = next;
+	}
+
+	return 0;
+}