why one should not use XoR or arithmetic operation to swap number???
Because it's inferior to using a temporary variable, and the original reason for avoiding a temporary variable is totally irrelevant unless you're on a severely memory constrained platform. And by "severely", I mean so much that you actually map out your register usage and design algorithms to avoid stack or heap use. Oh, and this also assumes that you're writing your code directly in assembly because C is just too heavy.
Then how to swap numbers without using temparory variable.