Swift is an open-source, general-purpose programming language developed by Apple Inc. It was first introduced in 2014 as a replacement for Objective-C for developing applications for Apple’s ecosystem, including iOS, macOS, watchOS, and tvOS. Swift was designed to be more modern, safe, and efficient while maintaining compatibility with existing Apple technologies.

Key features and concepts associated with Swift include:

1. Safety: Swift is known for its focus on safety. It includes features that help prevent common programming errors, such as null pointer dereferences and buffer overflows. This includes optional types, strong typing, and automatic memory management through reference counting.
2. Performance: Swift is designed to be a high-performance language. It achieves this by being compiled to native code, using a lightweight and efficient runtime, and optimizing for speed and memory usage.
3. Modern Syntax: Swift’s syntax is concise, clear, and expressive. It incorporates modern programming language features like closures, generics, pattern matching, and type inference, making code easier to read and write.
4. Interoperability: Swift is designed to work seamlessly with Objective-C, allowing developers to use Swift and Objective-C code together in the same project. This facilitates the gradual adoption of Swift in existing codebases.
5. Open Source: In 2015, Apple open-sourced Swift, making it available to a broader developer community. Swift’s open-source nature has led to contributions from individuals and organizations outside of Apple, resulting in a vibrant ecosystem.
6. Cross-Platform Development: While Swift was initially developed for Apple platforms, it has also been used for server-side development and cross-platform mobile app development through frameworks like SwiftUI and Flutter.
7. Standard Library: Swift comes with a rich standard library that provides common data types, algorithms, and utility functions for various tasks. It simplifies common programming tasks and encourages best practices.
8. Memory Management: Swift uses automatic reference counting (ARC) to manage memory, which helps developers avoid manual memory management while ensuring that memory is reclaimed when it’s no longer needed.
9. Community and Ecosystem: Swift has a growing and active community of developers who contribute to its ecosystem. This includes third-party libraries and packages available through the Swift Package Manager.
10. Playgrounds: Xcode, Apple’s integrated development environment (IDE), includes Swift Playgrounds, which allow developers to experiment with code interactively and see immediate results.
11. Debugging and Profiling: Xcode provides powerful debugging and profiling tools for Swift, making it easier to identify and fix issues in code.

Swift is the primary language for iOS, macOS, watchOS, and tvOS app development, and it has gained popularity not only within the Apple developer community but also in other domains. Its safety features, performance characteristics, and modern syntax have made it an attractive choice for a wide range of software development projects, from mobile apps and server-side applications to command-line tools and scripting.

To learn Swift for free go to docs.swift.org/swift-book/