What's the difference between the “global queue” and the “main queue” in GCD?

Question

Among some other ways, there are these two ways to get queues in GCD:

dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_g         


        

Answer 1

Global dispatch queue :

1. Tasks in concurrent queue executes concurrently [background threads]
2. Tasks are still started in the order that they were added to the queue

Main dispatch queue :

1. Available serial queue that executes tasks on the application's main thread.
2. It is usually called from a background queue when some background processing has finished and the user interface needs to be updated.