diff --git a/4th Sem (Design and Analysis of algorithm)/1a.java b/4th Sem (Design and Analysis of algorithm)/1a.java
new file mode 100644
index 0000000..d74e69c
--- /dev/null
+++ b/4th Sem (Design and Analysis of algorithm)/1a.java	
@@ -0,0 +1,43 @@
+import java.util.Scanner;
+public class Student
+{
+private String usn, name, branch, phone;
+public Student(String usn, String name, String branch, String phone)
+{
+super();
+this.usn = usn;
+this.name = name;
+this.branch = branch;
+this.phone = phone;
+}
+@Override
+public String toString()
+{
+return "Student [USN = " + usn + ", NAME = " + name + ", BRANCH = " + branch
++ ", PHONE NUMBER = " + phone + "]";
+}
+public static void main(String args[])
+{
+int i;
+String usn, branch, name, phone;
+Scanner s = new Scanner(System.in);
+System.out.println("Enter number of Students: ");
+int n = s.nextInt();
+Student[] students = new Student[n + 1];
+for(i = 1; i<= n; i ++)
+{
+System.out.println("Enter student "+ i +" details\n");
+System.out.println("Give Student Details USN, Name, Branch, Phone Number");
+usn = s.next();
+name = s.next();
+branch = s.next();
+phone = s.next();
+students[i] = new Student(usn, name, branch, phone);
+}
+System.out.println("DATABASE:");
+for(i = 1; i <= n; i ++)
+{
+System.out.println(students[i]);
+}
+}
+}
diff --git a/4th Sem (Design and Analysis of algorithm)/3a.java b/4th Sem (Design and Analysis of algorithm)/3a.java
new file mode 100644
index 0000000..f7829bd
--- /dev/null
+++ b/4th Sem (Design and Analysis of algorithm)/3a.java	
@@ -0,0 +1,22 @@
+import java.util.*;
+public class Division
+{
+public static void main(String[] args)
+{
+int a,b,quotient;
+Scanner s = new Scanner(System.in);
+System.out.println("Enter Numerator:" );
+a = s.nextInt();
+System.out.println("Enter Denominator:" );
+b = s.nextInt();
+try
+{
+quotient=a/b;
+System.out.println("Quotient=" + quotient);
+}
+catch(ArithmeticException ae)
+{
+System.out.println(ae);
+}
+}
+}
diff --git a/7th sem (Machine Learning)/lab2.py b/7th sem (Machine Learning)/lab2.py
new file mode 100644
index 0000000..d111be0
--- /dev/null
+++ b/7th sem (Machine Learning)/lab2.py	
@@ -0,0 +1,117 @@
+class Graph:
+    def __init__(self, graph, heuristicNodeList, startNode): #instantiate graph object with graph topology, heuristic values, start node
+
+        self.graph = graph
+        self.H=heuristicNodeList
+        self.start=startNode
+        self.parent={}
+        self.status={}
+        self.solutionGraph={}
+
+    def applyAOStar(self): # starts a recursive AO* algorithm
+        self.aoStar(self.start, False)
+
+    def getNeighbors(self, v): # gets the Neighbors of a given node
+        return self.graph.get(v,'')
+
+    def getStatus(self,v): # return the status of a given node
+        return self.status.get(v,0)
+
+    def setStatus(self,v, val): # set the status of a given node
+        self.status[v]=val
+
+    def getHeuristicNodeValue(self, n):
+        return self.H.get(n,0) # always return the heuristic value of a given node
+
+    def setHeuristicNodeValue(self, n, value):
+        self.H[n]=value # set the revised heuristic value of a given node
+
+
+    def printSolution(self):
+        print("FOR GRAPH SOLUTION, TRAVERSE THE GRAPH FROM THE STARTNODE:",self.start)
+        print("------------------------------------------------------------")
+        print(self.solutionGraph)
+        print("------------------------------------------------------------")
+
+    def computeMinimumCostChildNodes(self, v): # Computes the Minimum Cost of child nodes of a given node v
+        minimumCost=0
+        costToChildNodeListDict={}
+        costToChildNodeListDict[minimumCost]=[]
+        flag=True
+        for nodeInfoTupleList in self.getNeighbors(v): # iterate over all the set of child node/s
+            cost=0
+            nodeList=[]
+            for c, weight in nodeInfoTupleList:
+                cost=cost+self.getHeuristicNodeValue(c)+weight
+                nodeList.append(c)
+        
+            if flag==True: # initialize Minimum Cost with the cost of first set of child node/s
+                minimumCost=cost
+                costToChildNodeListDict[minimumCost]=nodeList # set the Minimum Cost child node/s
+                flag=False
+            else: # checking the Minimum Cost nodes with the current Minimum Cost
+                if minimumCost>cost:
+                    minimumCost=cost
+                    costToChildNodeListDict[minimumCost]=nodeList # set the Minimum Cost child node/s
+
+
+        return minimumCost, costToChildNodeListDict[minimumCost] # return Minimum Cost and Minimum Cost child node/s
+
+
+    def aoStar(self, v, backTracking): # AO* algorithm for a start node and backTracking status flag
+
+        print("HEURISTIC VALUES :", self.H)
+        print("SOLUTION GRAPH :", self.solutionGraph)
+        print("PROCESSING NODE :", v)
+
+        print("-----------------------------------------------------------------------------------------")
+    
+        if self.getStatus(v) >= 0: # if status node v >= 0, compute Minimum Cost nodes of v
+            minimumCost, childNodeList = self.computeMinimumCostChildNodes(v)
+            self.setHeuristicNodeValue(v, minimumCost)
+            self.setStatus(v,len(childNodeList))
+
+            solved=True # check the Minimum Cost nodes of v are solved
+        
+            for childNode in childNodeList:
+                self.parent[childNode]=v
+                if self.getStatus(childNode)!=-1:
+                    solved=solved & False
+
+            if solved==True: # if the Minimum Cost nodes of v are solved, set the current node status as solved(-1)
+                self.setStatus(v,-1)
+                self.solutionGraph[v]=childNodeList # update the solution graph with the solved nodes which may be a part of solution
+
+
+            if v!=self.start: # check the current node is the start node for backtracking the current node value
+                self.aoStar(self.parent[v], True) # backtracking the current node value with backtracking status set to true
+
+            if backTracking==False: # check the current call is not for backtracking
+                for childNode in childNodeList: # for each Minimum Cost child node
+                    self.setStatus(childNode,0) # set the status of child node to 0(needs exploration)
+                    self.aoStar(childNode, False) # Minimum Cost child node is further explored with backtracking status as false
+
+
+
+h1 = {'A': 1, 'B': 6, 'C': 2, 'D': 12, 'E': 2, 'F': 1, 'G': 5, 'H': 7, 'I': 7, 'J':1, 'T': 3}
+graph1 = {
+    'A': [[('B', 1), ('C', 1)], [('D', 1)]],
+    'B': [[('G', 1)], [('H', 1)]],
+    'C': [[('J', 1)]],
+    'D': [[('E', 1), ('F', 1)]],
+    'G': [[('I', 1)]]
+}
+G1= Graph(graph1, h1, 'A')
+G1.applyAOStar()
+G1.printSolution()
+
+h2 = {'A': 1, 'B': 6, 'C': 12, 'D': 10, 'E': 4, 'F': 4, 'G': 5, 'H': 7} # Heuristic values of Nodes
+graph2 = { # Graph of Nodes and Edges
+    'A': [[('B', 1), ('C', 1)], [('D', 1)]], # Neighbors of Node 'A', B, C & D with repective weights
+    'B': [[('G', 1)], [('H', 1)]], # Neighbors are included in a list of lists
+    'D': [[('E', 1), ('F', 1)]] # Each sublist indicate a "OR" node or "AND" nodes
+}
+
+G2 = Graph(graph2, h2, 'A') # Instantiate Graph object with graph, heuristic values and start Node
+G2.applyAOStar() # Run the AO* algorithm
+G2.printSolution() # print the solution graph as AO* Algorithm search