Write a program that prompts the user to enter a positive integer and calculates its factorial. The factorial of a positive integer 'n' is denoted as 'n!' and is calculated by multiplying all the integers from 1 to 'n' together. For example, the factorial of 5 (denoted as 5!) is calculated as 1 x 2 x 3 x 4 x 5.
The program should display the factorial value if the input is a positive number, or display a message stating that the factorial does not exist for negative numbers. Additionally, for an input of zero, the program should output that the factorial of 0 is 1.
Source Code
num = int(input("Enter a number: "))
factorial = 1
for i in range(1, num + 1):
factorial *= i
if num == 0:
print("Factorial of 0 is 1.")
elif num < 0:
print("Factorial does not exist for negative numbers.")
else:
print("Factorial of", num, "is", factorial)
Output
Enter a number: 5
Factorial of 5 is 120
Enter a number: 0
Factorial of 0 is 1.
Enter a number: -7
Factorial does not exist for negative numbers.