What if I don't write default in switch case?

Question

int a = 10;
switch(a){
case 0:
    printf(\"case 0\");
    break;
case 1:
    printf(\"case 1\");
    break;
}

Is the above code valid?

If

Answer 1

It is perfectly legal code. If a is neither 0 or 1, then the switch block will be entirely skipped.