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skills/programming-swift/GuidedTour/AboutSwift.md

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+# About Swift
+
+Understand the high-level goals of the language.
+
+Swift is a fantastic way to write software
+for phones, tablets, desktops, servers,
+or anything else that runs code.
+It's a safe and fast programming language
+that combines the best in modern language thinking
+with wisdom from a diverse open source community.
+
+Swift is friendly to new programmers,
+without sacrificing the power and flexibility
+that experienced programmers need.
+It's an industrial-quality programming language
+that's as expressive and enjoyable as a scripting language.
+The compiler is optimized for performance
+and the language is optimized for development,
+without compromising on either.
+
+Swift defines away large classes of common programming errors
+by adopting modern programming patterns:
+
+- Variables are always initialized before use.
+- Array indices are checked for out-of-bounds errors.
+- Integers are checked for overflow.
+- Optionals ensure that `nil` values are handled explicitly.
+- Memory is managed automatically.
+- Error handling allows controlled recovery from unexpected failures.
+
+Swift code is compiled and optimized to get the most out of modern hardware.
+The syntax and standard library have been designed
+based on the guiding principle that
+the obvious way to write your code should also perform the best.
+Its combination of safety and speed make Swift an excellent choice for
+everything from "Hello, world!" to an entire operating system.
+
+Swift combines a modern, lightweight syntax
+that's familiar for developers coming from other popular languages
+with powerful features like type inference and pattern matching,
+allowing complex ideas to be expressed in a clear and concise manner.
+As a result, code is easier to read, write, and maintain.
+
+Swift continues to evolve with thoughtful new features and powerful capabilities.
+The goals for Swift are ambitious.
+We can’t wait to see what you create with it.
+
+<!--
+This source file is part of the Swift.org open source project
+
+Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+Licensed under Apache License v2.0 with Runtime Library Exception
+
+See https://swift.org/LICENSE.txt for license information
+See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+-->

skills/programming-swift/GuidedTour/Compatibility.md

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+# Version Compatibility
+
+Learn what functionality is available in older language modes.
+
+This book describes Swift 6.2.1,
+the default version of Swift that's included in Xcode 26.1.
+You can use the Swift 6.2.1 compiler to build code
+that's written in Swift 6.2.1, Swift 5, Swift 4.2, or Swift 4.
+
+When you use the Swift 6.2.1 compiler
+to build code that uses the Swift 5 language mode,
+you can use the new features from Swift 6.2.1 ---
+they're enabled either by default or by an upcoming feature flag.
+However, to enable strict concurrency checking,
+you need to upgrade to the Swift 6.2.1 language mode.
+
+In addition,
+when you use Xcode 15.3 to build Swift 4 and Swift 4.2 code,
+most Swift 5 functionality is still available.
+That said,
+the following changes are available only to code
+that uses the Swift 5 language mode:
+
+- Functions that return an opaque type require the Swift 5.1 runtime.
+- The `try?` expression doesn't introduce an extra level of optionality
+  to expressions that already return optionals.
+- Large integer literal initialization expressions are inferred
+  to be of the correct integer type.
+  For example, `UInt64(0xffff_ffff_ffff_ffff)` evaluates to the correct value
+  rather than overflowing.
+
+Concurrency requires the Swift 5 language mode
+and a version of the Swift standard library
+that provides the corresponding concurrency types.
+On Apple platforms, set a deployment target
+of at least iOS 13, macOS 10.15, tvOS 13, watchOS 6, or visionOS 1.
+
+A target written in Swift 6.2.1 can depend on
+a target that's written in Swift 5, Swift 4.2 or Swift 4,
+and vice versa.
+This means, if you have a large project
+that's divided into multiple frameworks,
+you can migrate your code to a newer language version
+one framework at a time.
+
+<!--
+This source file is part of the Swift.org open source project
+
+Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+Licensed under Apache License v2.0 with Runtime Library Exception
+
+See https://swift.org/LICENSE.txt for license information
+See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+-->