Char pointer declaration inside and outside main()

Question

The program that I wrote is :

char* str_1;
void main()
{
    char* str_2;
    printf("STR_1 Address of pointer : %p\n", &str_1);
    printf("STR_2 Address of pointer : %p\n", &str_2);
    printf("STR_1 pointer : %p\n", str_1);
    printf("STR_2 pointer : %p\n", str_2);
}

And the output is the following :

STR_1 Address of pointer : 00404048
STR_2 Address of pointer : 0028FF1C
STR_1 pointer : 00000000
STR_2 pointer : 7EFDE000

How can we explain this ?

Answer 1

Variables defined at namespace scope are value-initialized by default, that's why str_1 points to NULL.

str_2 is not initialized, so the line

printf("STR_2 pointer : %p\n", str_2);

is actually undefined behavior. A garbage value is printed.