why 0! = 1 ?

Question

Computer Mathematical question

Answer 1

The Position of the Spaces makes a big difference:

(1! = 1) == true
(1 != 1) == false

Answer 2

https://www.youtube.com/watch?v=X32dce7_D48

Answer 3

Thanks to you all guys Amogh Jan Markus Sebastian Keßler