1. output is Novell

2. output is Hello World World

because after 1st printf fork is executed .This creates the child process so child will execute 2nd printf & oncemore  by parent process.Hence world is printed twice.

for 2nd question,

o/p - helloworldhelloworld. ( this is the case on linux)

because, execution of  first printf statment stores in buffer. 

fork , forks helloworld. thats why, its print 2 times helloworld.

In case if u placed "\n" line buffer in first printf .

like : printf("hello\n"); directly prints on standard buffer.

thats the reson it only forks the second printf.

o/p - hello

  world world