What does my unix shell mean by "[1]+ Stopped"?

Question

In my C program run on unix shell, I am using threads to do a task and then end, but sometimes I get these messages written on the shell saying [1]+ Stopped or [1]+ Done.

Does anyone know what these mean?

Answer 1

These messages are displayed by the shell when a task in this shell has been stopped or has finished its run.

Answer 2

It means a process launched in the background exited (Done) or received a stop signal (Stopped).

Answer 3

As said in other answers, these messages mean that your program launches subprocesses, and the console notifies you of their state. Aren't you confusing threads and processes, maybe? How do you create a "thread"? By using compiler options and the pthreads library, or by using the fork() primitive? If the latter, you're actually creating sub processes, not threads.