Where as in this case, the last line "Hello " executes first

launch

is async, so while in the first case the

delay(500L)

inside

coroutineScope

prevented the last line from executing until after

launch

had finished, it doesn't do that in this case

In the first case also, delay(500L) is inside launch which is async. So why it prevents the last line to be executed?

coroutineScope

suspends until all inside coroutines are complete, including `launch`es

Does that mean suspending and blocking is same?

no, they are different -- suspending won't take up a thread, blocking will

Looks like, I am understanding a bit now. Thanks a lot for the help. I will explore a bit more. Hope you wouldn't mind if I have further basic doubts like this

launch is coroutine build of type Job so its return immedatly (like future of comptetebalefuture) so the main is pass the second instruction (println("hello")) and not wait for launch to complete, also launch is delay fo 1 sec and this is an other reason the print ("hello") on first, delay is function that execute is separate thread (with executor named "scheduler") so the main-thread will be free to continue execution (not println("world")) because launch in this case is suspended (blocking) until delay finish) so main-thread pass to rest of your code (println("hello")), when delay finish its resume in main-thread (context of resume by default is the context of caller and in this case is main-thread you can change it if you implement continuation interface) and println("world")