diff --git a/data_structures/stack_using_linked_list.cpp b/data_structures/stack_using_linked_list.cpp
index 202c5c9b6..a87e6efb0 100644
--- a/data_structures/stack_using_linked_list.cpp
+++ b/data_structures/stack_using_linked_list.cpp
@@ -15,7 +15,7 @@ void push(int x) {
 }
 
 void pop() {
-    if (top_var == NULL) {
+    if (top_var == nullptr) {
         std::cout << "\nUnderflow";
     } else {
         node *t = top_var;
@@ -27,14 +27,14 @@ void pop() {
 
 void show() {
     node *t = top_var;
-    while (t != NULL) {
+    while (t != nullptr) {
         std::cout << t->val << "\n";
         t = t->next;
     }
 }
 
 int main() {
-    int ch, x;
+    int ch = 0, x = 0;
     do {
         std::cout << "\n0. Exit or Ctrl+C";
         std::cout << "\n1. Push";
@@ -42,17 +42,23 @@ int main() {
         std::cout << "\n3. Print";
         std::cout << "\nEnter Your Choice: ";
         std::cin >> ch;
-        switch(ch){
-        case 0: break;
-        case 1: std::cout << "\nInsert : ";
+        switch (ch) {
+            case 0:
+                break;
+            case 1:
+                std::cout << "\nInsert : ";
                 std::cin >> x;
                 push(x);
                 break;
-        case 2: pop();
+            case 2:
+                pop();
                 break;
-        case 3: show();
+            case 3:
+                show();
+                break;
+            default:
+                std::cout << "Invalid option!\n";
                 break;
-        default: std::cout << "Invalid option!\n"; break;
         }
     } while (ch != 0);