diff --git a/OOP/Java/Lab/Week13/Calculator.java b/OOP/Java/Lab/Week13/Calculator.java
new file mode 100644
index 0000000..36fe399
--- /dev/null
+++ b/OOP/Java/Lab/Week13/Calculator.java
@@ -0,0 +1,122 @@
+import java.awt.*;
+import java.awt.event.*;
+import javax.swing.*;
+
+public class Calculator extends JFrame implements ActionListener {
+
+    private JTextField display;
+    private double result = 0;
+    private String operator = "=";
+    private boolean calculating = true;
+
+    public Calculator() {
+        display = new JTextField("0", 20);
+        display.setHorizontalAlignment(JTextField.RIGHT);
+        display.setEditable(false);
+
+        // Create panel with grid layout for buttons
+        JPanel buttonPanel = new JPanel();
+        buttonPanel.setLayout(new GridLayout(4, 4, 5, 5));
+
+        String[] buttonLabels = {
+            "7",
+            "8",
+            "9",
+            "/",
+            "4",
+            "5",
+            "6",
+            "*",
+            "1",
+            "2",
+            "3",
+            "-",
+            "0",
+            ".",
+            "=",
+            "+",
+        };
+
+        for (String label : buttonLabels) {
+            JButton button = new JButton(label);
+            buttonPanel.add(button);
+            button.addActionListener(this);
+        }
+
+        JButton clearButton = new JButton("C");
+        clearButton.addActionListener(e -> {
+            result = 0;
+            operator = "=";
+            calculating = true;
+            display.setText("0");
+        });
+
+        // Layout
+        setLayout(new BorderLayout(5, 5));
+        add(display, BorderLayout.NORTH);
+        add(buttonPanel, BorderLayout.CENTER);
+        add(clearButton, BorderLayout.SOUTH);
+
+        setTitle("Simple Calculator");
+        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        pack();
+        setLocationRelativeTo(null);
+    }
+
+    public void actionPerformed(ActionEvent event) {
+        String command = event.getActionCommand();
+
+        if (
+            (command.charAt(0) >= '0' && command.charAt(0) <= '9') ||
+            command.equals(".")
+        ) {
+            if (calculating) {
+                display.setText(command);
+            } else {
+                display.setText(display.getText() + command);
+            }
+            calculating = false;
+        } else {
+            if (calculating) {
+                if (command.equals("-")) {
+                    display.setText(command);
+                    calculating = false;
+                } else {
+                    operator = command;
+                }
+            } else {
+                double x = Double.parseDouble(display.getText());
+                calculate(x);
+                operator = command;
+                calculating = true;
+            }
+        }
+    }
+
+    private void calculate(double n) {
+        switch (operator) {
+            case "+":
+                result += n;
+                break;
+            case "-":
+                result -= n;
+                break;
+            case "*":
+                result *= n;
+                break;
+            case "/":
+                result /= n;
+                break;
+            case "=":
+                result = n;
+                break;
+        }
+        display.setText("" + result);
+    }
+
+    public static void main(String[] args) {
+        SwingUtilities.invokeLater(() -> {
+            new Calculator().setVisible(true);
+        });
+    }
+}
diff --git a/OOP/Java/Lab/Week13/Credentials.java b/OOP/Java/Lab/Week13/Credentials.java
new file mode 100644
index 0000000..2d40881
--- /dev/null
+++ b/OOP/Java/Lab/Week13/Credentials.java
@@ -0,0 +1,54 @@
+import javafx.application.Application;
+import javafx.geometry.Insets;
+import javafx.scene.Scene;
+import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.control.PasswordField;
+import javafx.scene.control.TextField;
+import javafx.scene.layout.GridPane;
+import javafx.scene.text.Text;
+import javafx.stage.Stage;
+
+public class Credentials extends Application {
+
+    @Override
+    public void start(Stage primaryStage) {
+        primaryStage.setTitle("Login Form");
+
+        GridPane grid = new GridPane();
+        grid.setPadding(new Insets(10, 10, 10, 10));
+        grid.setVgap(5);
+        grid.setHgap(5);
+
+        Label username = new Label("Username:");
+        grid.add(username, 0, 0);
+
+        TextField userTextField = new TextField();
+        grid.add(userTextField, 1, 0);
+
+        Label password = new Label("Password:");
+        grid.add(password, 0, 1);
+
+        PasswordField passwordField = new PasswordField();
+        grid.add(passwordField, 1, 1);
+
+        Button signInButton = new Button("Sign in");
+        grid.add(signInButton, 1, 2);
+
+        Text welcomeText = new Text();
+        grid.add(welcomeText, 1, 3);
+
+        signInButton.setOnAction(e -> {
+            String name = userTextField.getText();
+            welcomeText.setText("Welcome " + name);
+        });
+
+        Scene scene = new Scene(grid, 300, 200);
+        primaryStage.setScene(scene);
+        primaryStage.show();
+    }
+
+    public static void main(String[] args) {
+        launch(args);
+    }
+}
diff --git a/OOP/Java/Lab/Week13/EmployeeMoney.java b/OOP/Java/Lab/Week13/EmployeeMoney.java
new file mode 100644
index 0000000..2bd06d2
--- /dev/null
+++ b/OOP/Java/Lab/Week13/EmployeeMoney.java
@@ -0,0 +1,95 @@
+import javafx.application.Application;
+import javafx.geometry.Insets;
+import javafx.scene.Scene;
+import javafx.scene.control.Label;
+import javafx.scene.layout.VBox;
+import javafx.stage.Stage;
+
+class Employee {
+
+    private String name;
+    private String empID;
+    private String designation;
+    private double basicPay;
+    private double DA;
+    private double HRA;
+    private double PF;
+    private double LIC;
+    private double netSalary;
+
+    public Employee(
+        String name,
+        String empID,
+        String designation,
+        double basicPay,
+        double LIC
+    ) {
+        this.name = name;
+        this.empID = empID;
+        this.designation = designation;
+        this.basicPay = basicPay;
+        this.LIC = LIC;
+
+        this.DA = 0.4 * basicPay;
+        this.HRA = 0.15 * basicPay;
+        this.PF = 0.12 * basicPay;
+
+        this.netSalary = basicPay + DA + HRA - PF - LIC;
+    }
+
+    public String getEmployeeInfo() {
+        return String.format(
+            """
+            Employee Details:
+            Name: %s
+            Employee ID: %s
+            Designation: %s
+            Basic Pay: $%.2f
+            DA: $%.2f
+            HRA: $%.2f
+            PF: $%.2f
+            LIC: $%.2f
+            Net Salary: $%.2f
+            """,
+            name,
+            empID,
+            designation,
+            basicPay,
+            DA,
+            HRA,
+            PF,
+            LIC,
+            netSalary
+        );
+    }
+}
+
+public class EmployeeInfoApp extends Application {
+
+    @Override
+    public void start(Stage primaryStage) {
+        Employee emp = new Employee(
+            "John Doe",
+            "E123",
+            "Software Engineer",
+            50000,
+            2000
+        );
+
+        Label infoLabel = new Label(emp.getEmployeeInfo());
+        infoLabel.setStyle("-fx-font-family: monospace;");
+
+        VBox root = new VBox(10);
+        root.setPadding(new Insets(10));
+        root.getChildren().add(infoLabel);
+
+        Scene scene = new Scene(root, 300, 400);
+        primaryStage.setTitle("Employee Information");
+        primaryStage.setScene(scene);
+        primaryStage.show();
+    }
+
+    public static void main(String[] args) {
+        launch(args);
+    }
+}
diff --git a/OOP/Java/Lab/Week13/GCD.java b/OOP/Java/Lab/Week13/GCD.java
new file mode 100644
index 0000000..d71041d
--- /dev/null
+++ b/OOP/Java/Lab/Week13/GCD.java
@@ -0,0 +1,65 @@
+import javafx.application.Application;
+import javafx.geometry.Pos;
+import javafx.scene.Scene;
+import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.control.TextField;
+import javafx.scene.layout.VBox;
+import javafx.stage.Stage;
+
+public class GCDCalculator extends Application {
+
+    @Override
+    public void start(Stage primaryStage) {
+        TextField num1Field = new TextField();
+        num1Field.setPromptText("Enter first number");
+        TextField num2Field = new TextField();
+        num2Field.setPromptText("Enter second number");
+
+        Label resultLabel = new Label();
+        Button calculateButton = new Button("Calculate GCD");
+
+        calculateButton.setOnAction(e -> {
+            try {
+                int num1 = Integer.parseInt(num1Field.getText());
+                int num2 = Integer.parseInt(num2Field.getText());
+
+                if (num1 <= 0 || num2 <= 0) {
+                    resultLabel.setText("Please enter positive integers only");
+                    return;
+                }
+
+                int gcd = calculateGCD(num1, num2);
+                resultLabel.setText(
+                    String.format("GCD of %d and %d is: %d", num1, num2, gcd)
+                );
+            } catch (NumberFormatException ex) {
+                resultLabel.setText("Please enter valid integers");
+            }
+        });
+
+        VBox root = new VBox(10);
+        root.setAlignment(Pos.CENTER);
+        root
+            .getChildren()
+            .addAll(num1Field, num2Field, calculateButton, resultLabel);
+
+        Scene scene = new Scene(root, 300, 200);
+        primaryStage.setTitle("GCD Calculator");
+        primaryStage.setScene(scene);
+        primaryStage.show();
+    }
+
+    private int calculateGCD(int a, int b) {
+        while (b != 0) {
+            int temp = b;
+            b = a % b;
+            a = temp;
+        }
+        return a;
+    }
+
+    public static void main(String[] args) {
+        launch(args);
+    }
+}
diff --git a/OOP/Java/Lab/Week13/Multiplier.java b/OOP/Java/Lab/Week13/Multiplier.java
new file mode 100644
index 0000000..707c172
--- /dev/null
+++ b/OOP/Java/Lab/Week13/Multiplier.java
@@ -0,0 +1,66 @@
+import javafx.application.Application;
+import javafx.geometry.Insets;
+import javafx.scene.Scene;
+import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.control.TextArea;
+import javafx.scene.control.TextField;
+import javafx.scene.layout.FlowPane;
+import javafx.stage.Stage;
+
+public class Multiplier extends Application {
+
+    @Override
+    public void start(Stage primaryStage) {
+        FlowPane root = new FlowPane();
+        root.setPadding(new Insets(10));
+        root.setHgap(10);
+        root.setVgap(10);
+
+        Label inputLabel = new Label("Enter a number:");
+        TextField numberInput = new TextField();
+        Button generateButton = new Button("Generate Table");
+        TextArea resultArea = new TextArea();
+        resultArea.setPrefRowCount(12);
+        resultArea.setPrefColumnCount(20);
+        resultArea.setEditable(false);
+
+        generateButton.setOnAction(e -> {
+            try {
+                int number = Integer.parseInt(numberInput.getText());
+                StringBuilder table = new StringBuilder();
+                table
+                    .append("Multiplication Table for ")
+                    .append(number)
+                    .append("\n\n");
+
+                for (int i = 1; i <= 10; i++) {
+                    table
+                        .append(number)
+                        .append(" x ")
+                        .append(i)
+                        .append(" = ")
+                        .append(number * i)
+                        .append("\n");
+                }
+
+                resultArea.setText(table.toString());
+            } catch (NumberFormatException ex) {
+                resultArea.setText("Please enter a valid integer");
+            }
+        });
+
+        root
+            .getChildren()
+            .addAll(inputLabel, numberInput, generateButton, resultArea);
+
+        Scene scene = new Scene(root, 300, 400);
+        primaryStage.setTitle("Multiplication Table Generator");
+        primaryStage.setScene(scene);
+        primaryStage.show();
+    }
+
+    public static void main(String[] args) {
+        launch(args);
+    }
+}