Process Groups

[NickJohnson]

I'm going to be writing some sort of process group manager in the near future, but I'm having trouble deciding how complex to make it. Right now, all I want to be able to do is kill the foreground process with a key command (like Ctrl-C) via signals (which I already have working), and I think that would be possible to implement with only one foreground process, which could be managed by the terminal driver. However, since I haven't really used process groups in my experience with *nix systems, I don't know what other kind of functionality often depends on them. So, basically, two questions: what are all the things that process groups are used for? Do I ever need more than one process to be in the foreground per terminal?