Initialize the first elememt of the structure or the whole structure?

Question

all:
In C language:

struct A  
{
    int a;
    int b;
};

A aa = {0};  

This statement initialize aa.a only or initialize the whole struture? Or the behavior depends on Compiler?
Thanks in advance!

Answer 1

One more ex:
struct A  
{
    int a;
    int b;
};

struct A aa = {5}; 

This will initialize the whole structure but aa.b will be initialized to 0. If you initialize only few members of a structure then all other members of that will be automatically initialized to 0.