iOS

iOS is Apple's mobile operating system, powering the iPhone, iPad (as iPadOS, a close derivative), and iPod touch. iOS is a closed source platform with first-party SDKs, a curated App Store as the distribution channel, and tight hardware-software integration that defines the experience.

Core platform pieces

• SDK and language. Native development uses Swift (modern) or Objective-C (legacy), with Xcode as the IDE.
• UI frameworks. SwiftUI (declarative, modern) and UIKit (imperative, mature) are the two paths for building screens.
• Frameworks. Foundation, Core Data, Core Animation, AVFoundation, MapKit, HealthKit, ARKit, and many more.
• App lifecycle. Apps run in sandboxes; background execution is limited; the system manages memory, CPU, and energy aggressively.
• Distribution. The App Store is the only sanctioned distribution channel (with TestFlight for betas and enterprise programs for internal apps).

Cross-platform alternatives

Many teams build iOS apps with cross-platform toolchains:

• React Native, Flutter, Kotlin Multiplatform Mobile, .NET MAUI, Capacitor, Ionic.