Can I put code inside switch(), above or under case x {}

Assume:

switch ( test ) {

  // Set some variables, call some functions ?
  int var x = 1 ;
  int var y = function(x) ;
  //

  case 1 : 
    // Process for test = 1
    ...
    break;

  case 5 : 
    // Process for test = 5
    ...
    break;

  default : 
    // Process for all other cases.
    ...

}

Is it 'legal' to execute that extra bit of code I added before the first case: ? I've never seen this in examples.