How to implement sequential task execution using GCD?

To execute tasks sequentially using GCD (Grand Central Dispatch), you can use a serial queue. In such a queue, tasks are executed one after another in the order they are added.

Example in Swift:

let serialQueue = DispatchQueue(label: "com.example.serialQueue")

serialQueue.async {
    print("Task 1")
}

serialQueue.async {
    print("Task 2")
}

serialQueue.async {
    print("Task 3")
}

In this example, tasks will be executed strictly sequentially: first "Task 1", then "Task 2", and then "Task 3". If a global queue with concurrent mode is used, tasks may run in parallel, which does not guarantee order.