Principles of protocol-oriented and functional programming in Swift 5.1 for operating systems macOS, iOS and iPadOS are considered. The Xcode 11.2 development environment and Apple's latest technology, SwiftUI, are described in detail. Techniques for designing and developing programs for macOS using the Cocoa framework, mobile applications using the Cocoa Touch framework, principles for creating projects with the Storyboard interface are described. The chapters contain solution exercises and code samples for novice programmers.