diff --git a/simplecalculator.py b/simplecalculator.py
index fd89db5..e46de55 100644
--- a/simplecalculator.py
+++ b/simplecalculator.py
@@ -1,29 +1,50 @@
-print("Simple Calculator")
-print("Select an Operation")
-print("1. Addition")
-print("2. Substraction")
-print("3. Multiplication")
-print("4. Division")
-print("0. End the Program")
+def add(a, b):
+    return a + b
 
-while True:
-    operation = int(input("Enter choice(1/2/3/4/0) >>  "))
-    num1 = float(input("Enter num1>>  "))
-    num2 = float(input("Enter num2>>  "))
-    
-    if operation==1:
-        print(num1+num2)
-    elif operation==2:
-        print(num1-num2)
-    elif operation==3:
-        print(num1*num2)
-    elif operation==4:
-        print(num1/num2)
-    elif operation==0:
-        break
+def subtract(a, b):
+    return a - b
+
+def multiply(a, b):
+    return a * b
+
+def divide(a, b):
+    if b != 0:
+        return a / b
     else:
-        print("Invalid Option! Please Try Again")
+        return "Error: Division by zero is undefined."
 
+def main():
+    print("Simple Calculator")
+    print("Select an Operation:")
+    print("1. Addition")
+    print("2. Subtraction")
+    print("3. Multiplication")
+    print("4. Division")
+    print("0. End the Program")
 
+    while True:
+        try:
+            operation = int(input("\nEnter choice (1/2/3/4/0): "))
+            if operation == 0:
+                print("Ending the program.")
+                break
+            
+            if operation in (1, 2, 3, 4):
+                num1 = float(input("Enter first number: "))
+                num2 = float(input("Enter second number: "))
 
+                if operation == 1:
+                    print("Result:", add(num1, num2))
+                elif operation == 2:
+                    print("Result:", subtract(num1, num2))
+                elif operation == 3:
+                    print("Result:", multiply(num1, num2))
+                elif operation == 4:
+                    print("Result:", divide(num1, num2))
+            else:
+                print("Invalid option! Please choose a valid operation.")
+        except ValueError:
+            print("Invalid input! Please enter a number.")
 
+if __name__ == "__main__":
+    main()