So here we are. Apple appears to be finally opening up the threading APIs to developers on the iPhone.
I've had numerous conversations with colleagues since the iPhone came out and they've been all sorts of reactions as to why there's no multithreading. Actually, now that I've just typed multithreading let's get this straight. Multitasking relates to the human experience of doing multiple things at the same time; it is a use-case; it is something that I've been told (by my wife) that men can't do and women can (!).
Multithreading is the ability for an OS to cooperatively or pre-emptively (generally the latter) slice processor time between different paths of execution within and outside of a number of processes (generally applications).
The iPhone has supported multitasking and multithreading forever. The difference now is that Apple appears to have opened up the multithreading API to non-Apple developers. I've not seen the details on this, perhaps they've constrained the thread APIs in some interesting way with the goal of limiting battery usage, but it is a very good (and necessary) thing that there will now be multithreading.
One application that I'm really looking forward to using is Skype. Finally, we'll be able to receive Skype calls with the same experience of receiving regular mobile calls; so long as you're on a WiFi network of course. I think that this will be amazing as I'm never near my computer when someone wants to contact me via Skype. However, I always have my iPhone at hand of course.
I can't wait for SIP supporting applications to come along for the iPhone either. The prospect of receiving my home phone calls when away from home via VOIP is fantastic.
Oh and one thing I'd like to joyfully throw back at the multithreading doubters: get over it. Yes, multithreaded programming is harder but its just the way the world is. Multiple things happen at the same time. Embrace it.
Well done Apple. I look forward to iPhone 4.0.