switch statement - Can someone explain switching in Objective C -

i started learning objective c , don't understand switches. can please explain them me?

thanks

a switch statement meant used in place of if else statements

for example

int =4;  if(a == 1)     dosomething(); else if(a == 2)     dosomethingelse(); else if(a == 3)     blah(); else      caseunaccountedfor(); 

is equivalent to

int =4;  switch(a) { case 1:     dosomething();     break; case 2:     dosomethingelse();     break; case 3:     blah();     break; default:    caseunaccountedfor();     break; } 

if 1 of cases match, switch statement not automatically exited why there's break statement @ end of each case. case 'default' matches every other case besides ones explicitly list.