I'm reading a book about assembly x86 on the FASM assembler and the following sentence is introduced:

> 
> neg subtracts a signed integer operand from zero. The effect of this
>  instructon is to reverse the sign of the operand from positive to
>  negative or from negative to positive.
> 
> 
> 

It subtracts the operand from `0`, so if I have 6 ,`(0-6=-6)` and if I have -6 `(0-(-6)=6)`

Now, where does it save the reversed number? In the given operand? It doesn't say anymore about it in the book, so here I am wondering what's its purpose if we can't store it.