Is it correct to compare a real number with zero?

Question

C++ / C#

In fact, I know how to correctly compare real numbers, but I don’t understand how the following code will behave:

float x = 0.0;
...
if ( x == 0.0 ) { ... }

To be clear, assigning a null value to a variable occurs inside another function, and keeping track of this (for example, using flags) is not the best option: there is too much overhead. And it is necessary to check exactly for exactly zero value, because the logic of the program depends on it.
I would be grateful if you tell me about books that explain such subtleties =)

Answer 1

If it is the constant zero that is assigned, and not the result of any calculation, then comparison with zero is safe.

Answer 2

So it's safe to compare. The only question is - can a zero appear during calculations and will it not break the logic of the program?
It is better, of course, not to use 0.0, but 0.0f for this.