diff --git a/basics/03_control_flow/16_simple_calculator.py b/basics/03_control_flow/16_simple_calculator.py
new file mode 100644
index 0000000..96b5bb8
--- /dev/null
+++ b/basics/03_control_flow/16_simple_calculator.py
@@ -0,0 +1,42 @@
+def add(x, y):
+    return x + y
+
+def subtract(x, y):
+    return x - y
+
+def multiply(x, y):
+    return x * y
+
+def divide(x, y):
+    if y == 0:
+        print("Error: Cannot divide by zero!")
+        return None
+    return x / y
+
+def simple_calculator():
+    print("Select operation:")
+    print("1. Add")
+    print("2. Subtract")
+    print("3. Multiply")
+    print("4. Divide")
+
+    choice = input("Enter choice(1/2/3/4): ")
+
+    num1 = float(input("Enter first number: "))
+    num2 = float(input("Enter second number: "))
+
+    if choice == '1':
+        print(num1, "+", num2, "=", add(num1, num2))
+    elif choice == '2':
+        print(num1, "-", num2, "=", subtract(num1, num2))
+    elif choice == '3':
+        print(num1, "*", num2, "=", multiply(num1, num2))
+    elif choice == '4':
+        result = divide(num1, num2)
+        if result is not None:
+            print(num1, "/", num2, "=", result)
+    else:
+        print("Invalid Input")
+
+if __name__ == "__main__":
+    simple_calculator()
diff --git a/basics/04_functions/functions.py b/basics/04_functions/functions.py
new file mode 100644
index 0000000..e920203
--- /dev/null
+++ b/basics/04_functions/functions.py
@@ -0,0 +1,17 @@
+def add():
+    a = int(input("Enter the Number: "))
+    b = int(input("Enter the Number: "))
+    sum = a + b
+    print(sum)
+
+def subtract():
+    a = int(input("Enter first number: "))
+    b = int(input("Enter second number: "))
+    result = a - b
+    print(result)
+
+def multiply():
+    a = int(input("Enter first number: "))
+    b = int(input("Enter second number: "))
+    result = a * b
+    print(result)