Why its returning an error?
#include <stdio.h>
int call()
{
    extern int b;
    b=10;
    printf("%d",b);
}

int main ()
{
    int b=8;
    call();
    return 0;
}

/tmp/ccAsFhWX.o:meka.c:(.text+0x7): undefined reference to `_b' collect2: ld returned 1 exit status

#include <stdio.h>

static int b;

int call()
{
    b=10;
    printf("%d",b);
}

int main ()
{
    b=8;
    call();
    return 0;
}

#include <stdio.h>

extern int b;

void call()
{
    b = 10;
    printf("%dn",b);
}

int b = 8;

int main () {
    call();
    return 0;
}

#include <stdio.h>

void call (int *b)
{
    printf ("%dn", *b = 10);
}

int main () {
    int b = 8;
    call (&b);
    return 0;
}

void call (int *b) {
    *b = 10;
    printf("%d",*b);
}