# Grand Central Dispatch

# What is Grand central dispatch.

What is Concurrency?

  • Doing multiple things at the same time.

  • Taking advantage of number of cores available in multicore CPUs.

  • Running multiple programs in parallel.

Objectives of Concurrency

  • Running program in background without hogging CPU.
  • Define Tasks, Define Rules and let the system take the responsibility of performing them.
  • Improve responsiveness by ensuring that the main thread is free to respond to user events.

    Grand central dispatch – dispatch queues allows us to execute arbitrary blocks of code either asynchronously or synchronously All Dispatch Queues are first in – first out All the tasks added to dispatch queue are started in the order they were added to the dispatch queue.