How to call a change that does not change the output?

How would you call changes in the source code that, by their na开发者_Python百科ture, are never supposed to change the bin output? For instance, formatting or commenting.

This, to me, is a very simple example of Refactoring.

Code refactoring is the process of changing a computer program's source code without modifying its external functional behavior in order to improve some of the nonfunctional attributes of the software.