mjhjmtu

Computer Systems: A Programmer's Perspective says about two sections in a ELF relocatable object file:

• .data Initialized global and static C variables. Local C variables are maintained
  at run time on the stack and do not appear in either the .data or .bss
  sections.




• .bss Uninitialized global and static C variables, along with any global or static
  variables that are initialized to zero. This section occupies no actual space
  in the object file; it is merely a placeholder. Object file formats distinguish
  between initialized and uninitialized variables for space efficiency: unini-
  tialized variables do not have to occupy any actual disk space in the object
  file. At run time, these variables are allocated in memory with an initial
  value of zero.

Do "initialized" and "unitiailized" in the quote mean explicitly or implicitly or either?

if a global or static C variable is not explicitly initialized, but implicitly initialized, is it in .data or .bss section?

Does it matter whether the global or static C variable is implicitly initialized to zero or nonzero?

Thanks.