I think the problem was to illustrate the out of order sequence of the case statements and how it will effect the outcome. I think he was suppose to test the code and learn. Personly instead of changing x to equal 1 I would simply change the case 1: to case 0: and case 0: to case 1: keeping the outputs in the same order. If the point was to get all three to print. :P
Like :Code:main() { int x=0; switch(x) { case 0: printf( "One" ); case 1: printf( "Zero" ); case 2: printf( "Hello World" ); } }