How can full control over the execution flows in a program be ensured?

In iOS, several approaches can be used for full control over execution threads:

• GCD (Grand Central Dispatch) — allows creating and managing task queues (serial and concurrent), controlling priorities and synchronization.
• NSOperation and NSOperationQueue — a higher-level API that enables creating operations with dependencies, cancellation, and priorities.
• Threads (NSThread) — direct creation and management of threads, but this is a lower-level and more complex method.

For complete control, these tools can be combined, for example, by creating custom queues, managing priorities, and synchronization through semaphores or locks.

Example of creating and running a task in GCD:

let queue = DispatchQueue(label: "com.example.myqueue", qos: .userInitiated)
queue.async {
    // Code executed on a separate thread
    print("Task execution")
}

If more precise control is needed, DispatchWorkItem can be used for cancellation or tracking the task's status.