QoS.swift

import Foundation

// Perform loop 1 to 10 on global concurrent queue with 'userInteractive' QoS
DispatchQueue.global(qos: .userInteractive).async {
    for i in 1...10 {
        print("Queue 1: \(i)")
    }
}

// Perform loop 11 to 20 on global concurrent queue with 'userInitiated' QoS
DispatchQueue.global(qos: .userInitiated).async {
    for i in 11...20 {
        print("Queue 2: \(i)")
    }
}

// Perform loop 21 to 30 on global concurrent queue with 'utility' QoS
DispatchQueue.global(qos: .utility).async {
    for i in 21...30 {
        print("Queue 3: \(i)")
    }
}

// Perform loop 31 to 40 on global concurrent queue with 'background' QoS
DispatchQueue.global(qos: .background).async {
    for i in 31...40 {
        print("Queue 4: \(i)")
    }
}