C static variables and intialization

Question

Hi, If I have a global static variable x like in this code

 #include <stdio.h>
 #include <stdio.h>

 static int x;

 int main(void)
 {

 DO SOMETHING WITH x HERE

 x++;

 }

What will be difference if I opted to initialize x to a value first say as in

static int x = 0;  

before entering "main"?

In my first case where I didn't assign a value to x, does the compiler implicitly know that x is to be set to zero as it's a static variable? I heard that we can do this with static variables.

Thanks a lot...

Answer 1

Static variables are always implicitly initialized to zero, so there would be no difference in explicitly initializing x to zero.

Answer 2

static variables are automatically initialised to zero (i.e. as though you had assigned zero to them, causing floats and pointers to become 0.0 and NULL, respectively, even if the internal representation of those values is not all bits zero).

Answer 3

There is a nice answer here:

Just a short excerpt:

First of all in ISO C (ANSI C), all static and global variables must be initialized before the program starts. If the programmer didn't do this explicitly, then the compiler must set them to zero. If the compiler doesn't do this, it doesn't follow ISO C. Exactly how the variables are initialized is however unspecified by the standard.