Swift is a general-purpose, multi-paradigm, compiled programming language developed by Apple Inc. for iOS, iPadOS, macOS, watchOS, tvOS, and Linux. It is designed to work with Apple's Cocoa and Cocoa Touch frameworks and the large body of existing Objective-C code written for Apple products. Swift is built to be safe, fast, and expressive, with a modern syntax that encourages interactive development. Swift sample files are used to test the Swift compiler and Xcode development environment. iOS and macOS developers use them to verify UI rendering with SwiftUI or UIKit and to test logic capabilities in playgrounds. These files are also used to test Swift's interoperability with Objective-C and C++, ensuring seamless integration in legacy projects and modern applications.