Can you explain what a global queue is and how it is used in data processing systems?

The Global Dispatch Queue in iOS is a system thread pool provided by Grand Central Dispatch (GCD), used for executing tasks asynchronously.

It allows tasks to run in the background without blocking the main interface thread.

In iOS, there are several global queues with different priority levels (e.g., .userInitiated, .background).

Example of using a global queue to perform a task in the background:

DispatchQueue.global(qos: .background).async {
    // Long operation
    let result = performHeavyTask()
    DispatchQueue.main.async {
        // Update UI on the main thread
        updateUI(with: result)
    }
}

Thus, the global queue helps efficiently distribute the load and maintain app responsiveness.