资料来源 : Free On-Line Dictionary of Computing

switch statement
     
         (Or case statement, multi-way branch) A
        construct found in most {high-level languages} for selecting
        one of several possible blocks of code or branch destinations
        depending on the value of an expression.  An example in {C} is
     
        	switch (foo(x, y))
        	{
        	case 1:  printf("Hello\n");	/* fall through */
        	case 2:  printf("Goodbye\n"); break;
        	case 3:  printf("Fish\n"); break;
        	default: fprintf(stderr, "Odd foo value\n"); exit(1);
        	}
     
        The break statements cause execution to continue after the
        whole switch statemetnt.  The lack of a break statement after
        the first case means that execution will {fall through} into
        the second case.  Since this is a common programming error you
        should add a comment if it is intentional.
     
        If none of the explicit cases matches the expression value
        then the (optional) default case is taken.
     
        A similar construct in some {functional languages} returns the
        value of one of several expressions selected according to the
        value of the first expression.  A distant relation to the
        modern switch statement is {Fortran}'s {computed goto}.
     
        (1997-01-30)