human
Design and implement a program that utilizes the various types of loops available in programming languages like C, Java, and Python. Your program should:

1. Accept an integer input `n` from the user.
2. Use a `for` loop to calculate the sum of the first `n` natural numbers.
3. Use a `while` loop to calculate the factorial of `n`.
4. Use a `do-while` loop (or equivalent) to reverse the digits of the integer `n`. If the programming language does not support a `do-while` loop, use a different loop structure with the same functionality.
5. Implement a recursive function to find the `n`th Fibonacci number.
6. Use a nested loop to generate an `n` x `n` multiplication table.
7. Implement error handling to ensure the user inputs a positive integer, and include constraints to prevent integer overflow errors.
8. Optimize your code for readability, efficiency, and modularity.
9. Provide test cases to demonstrate the correctness and performance of your program.
gpt
Here is a Python implementation of the program:

```python
def get_input():
    while True:
        try:
            n = int(input("Enter a positive integer: "))
            if n > 0:
                return n
            else:
                print("Please enter a positive integer.")
        except ValueError:
            print("Invalid input. Please enter a positive integer.")

def sum_natural_numbers(n):
    return sum(range(1, n+1))

def factorial(n):
    fact = 1
    while n > 0:
        fact *= n
        n -= 1
    return fact

def reverse_integer(n):
    rev = 0
    while n > 0:
        rev = rev * 10 + n % 10
        n //= 10
    return rev

def fibonacci(n):
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)

def multiplication_table(n):
    for i in range(1, n+1):
        for j in range(1, n+1):
            print(i * j, end="\t")
        print()

def main():
    n = get_input()
    print("Sum of first", n, "natural numbers:", sum_natural_numbers(n))
    print("Factorial of", n, ":", factorial(n))
    print("Reverse of", n, ":", reverse_integer(n))
    print("Fibonacci number at position", n, ":", fibonacci(n))
    print("Multiplication table:")
    multiplication_table(n)

if __name__ == "__main__":
    main()
```

Test cases:

```
Enter a positive integer: 5
Sum of first 5 natural numbers: 15
Factorial of 5 : 120
Reverse of 5 : 5
Fibonacci number at position 5 : 5
Multiplication table:
1	2	3	4	5	
2	4	6	8	10	
3	6	9	12	15	
4	8	12	16	20	
5	10	15	20	25	

Enter a positive integer: 10
Sum of first 10 natural numbers: 55
Factorial of 10 : 3628800
Reverse of 10 : 1
Fibonacci number at position 10 : 55
Multiplication table:
1	2	3	4	5	6	7	8	9	10	
2	4	6	8	10	12	14	16	18	20	
3	6	9	12	15	18	21	24	27	30	
4	8	12	16	20	24	28	32	36	40	
5	10	15	20	25	30	35	40	45	50	
6	12	18	24	30	36	42	48	54	60	
7	14	21	28	35	42	49	56	63	70	
8	16	24	32	40	48	56	64	72	80	
9	18	27	36	45	54	63	72	81	90	
10	20	30	40	50	60	70	80	90	100	
```