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

As others have pointed out it is perfectly valid code. However, from a coding style perspective I prefer adding an empty default statement with a comment to make clear that I didn't unintentionally forget about it.

int a=10;
switch(a)
{
case 0: printf("case 0");
         break;
case 1: printf("case 1");
         break;
default: // do nothing;
         break;
}

The code generated with / without the default should be identical.

Answer 2

The syntax for a switch statement in C programming language is as follows:

switch(expression) {

   case constant-expression  :
      statement(s);
      break; /* optional */

   case constant-expression  :
      statement(s);
      break; /* optional */

   /* you can have any number of case statements */
   default : /* Optional */
   statement(s);
}