diff --git a/ExpressionTree.c b/ExpressionTree.c
index 328b160..1c29b3c 100644
--- a/ExpressionTree.c
+++ b/ExpressionTree.c
@@ -1,6 +1,7 @@
 #include<stdio.h>
 #include<stdlib.h>
 
+// EXPRESSION TREE
 struct node
 {
     char data;
@@ -49,7 +50,6 @@ void preorder(struct node *root)
         preorder(root->left);
         preorder(root->right);
     }
-
 }
 
 void inorder(struct node *root)
@@ -60,7 +60,6 @@ void inorder(struct node *root)
         printf("%c ",root->data);
         inorder(root->right);
     }
-
 }
 
 void postorder(struct node *root)
@@ -82,7 +81,7 @@ struct node *create_expression_tree(char *exp) // pass the postfix expression
 
     struct node *temp;
 
-    while(exp[i] != '\0')
+    while(exp[i] != '\0') // use example ABC*+ and trace
     {
         ch = exp[i];
         temp = (struct node *)malloc(sizeof(struct node));
@@ -112,13 +111,13 @@ int eval(struct node *root) // recursive function
         case '-': return(eval(root->left) - eval(root->right));
         case '*': return(eval(root->left) * eval(root->right));
         case '/': return(eval(root->left) / eval(root->right));
-        default: printf("%c = ",root->data);
+        default: printf("%c = \n",root->data);
         scanf("%d",&x);
         return x;
     }
 }
 
-void push(struct node **s, int *t, struct node *temp)
+void push(struct node **s, int *t, struct node *temp) // s-stack, t-top, ** as it is stack of nodes
 {
     ++(*t);
     s[*t] = temp;
diff --git a/QuickSort.py b/QuickSort.py
new file mode 100644
index 0000000..d54ecdb
--- /dev/null
+++ b/QuickSort.py
@@ -0,0 +1,31 @@
+def QuickSort(arr):
+
+    elements = len(arr)
+
+    #Base case
+    if elements < 2:
+        return arr
+
+    current_position = 0 #Position of the partitioning element
+
+    for i in range(1, elements): #Partitioning loop
+         if arr[i] <= arr[0]:
+              current_position += 1
+              temp = arr[i]
+              arr[i] = arr[current_position]
+              arr[current_position] = temp
+
+    temp = arr[0]
+    arr[0] = arr[current_position]
+    arr[current_position] = temp #Brings pivot to it's appropriate position
+
+    left = QuickSort(arr[0:current_position]) #Sorts the elements to the left of pivot
+    right = QuickSort(arr[current_position+1:elements]) #sorts the elements to the right of pivot
+
+    arr = left + [arr[current_position]] + right #Merging everything together
+
+    return arr
+
+array_to_be_sorted = [4,2,7,3,1,6]
+print("Original Array: ",array_to_be_sorted)
+print("Sorted Array: ",QuickSort(array_to_be_sorted))
diff --git a/Sets.py b/Sets.py
new file mode 100644
index 0000000..ef053ea
--- /dev/null
+++ b/Sets.py
@@ -0,0 +1,33 @@
+# add
+fruits = {'apple','banana','cherry'}
+fruits.add('orange')
+print(fruits)
+
+# pop - Remove a random item from the set
+fruits = {"apple", "banana", "cherry"}
+fruits.pop()
+print(fruits)
+
+# Union - Return a set that contains all items from both sets, duplicates are excluded
+x = {"apple", "banana", "cherry"}
+y = {"google", "microsoft", "apple"}
+z = x.union(y)
+print(z)
+
+# Intersection - Return a set that contains the items that exist in both set x, and set y
+x = {"apple", "banana", "cherry"}
+y = {"google", "microsoft", "apple"}
+z = x.intersection(y)
+print(z)
+
+# Difference - Return a set that contains the items that only exist in set x, and not in set y
+x = {"apple", "banana", "cherry"}
+y = {"google", "microsoft", "apple"}
+z = x.difference(y)
+print(z)
+
+# Symmertic Difference - Return a set that contains all items from both sets, except items that are present in both sets
+x = {"apple", "banana", "cherry"}
+y = {"google", "microsoft", "apple"}
+z = x.symmetric_difference(y)
+print(z)