When You Turn The iPhone On

iOS loads into memory and starts the services needed to run the phone.

Security, networking, notifications, storage, accounts, camera services, and background tasks begin automatically.

Power On
   |
   +-- iOS
   +-- Security
   +-- Network
   +-- Notifications
   +-- Storage
   +-- Apps
   +-- Home Screen

iPhone Runs Apps

iOS gives time and memory to apps as they run.

Apps may appear simple, but iOS is constantly managing what is open, paused, protected, or closed.

iOS
   |
   +-- Phone
   +-- Messages
   +-- Camera
   +-- Safari
   +-- Mail
   +-- Maps

Memory And Battery Matter

iPhone uses memory to keep apps ready and battery controls to protect power.

When resources are limited, iOS may pause background activity or reload an app later.

The Home Screen Is A Launcher

The Home Screen is where you open apps, widgets, folders, and shortcuts.

It is not the whole iPhone. It is the starting place for using iOS.

Home Screen
   |
   +-- Apps
   +-- Folders
   +-- Widgets
   +-- Shortcuts

Settings Control The Device

• Wi-Fi
• Bluetooth
• Display
• Storage
• Privacy
• Apple ID
• Accessibility

Understanding Settings is often more important than memorizing individual apps.

Privacy And Permissions

iOS controls what apps are allowed to access.

Camera, microphone, photos, contacts, location, Bluetooth, and notifications are protected by permissions.

iOS Is An Operating System

iOS runs on iPhones and manages apps, memory, storage, networking, security, cameras, microphones, batteries, screens, and user accounts.

Apple controls both the iPhone hardware and the iOS software, so the system is tightly integrated.

iPhone Runs Apps

Most of what people use every day are apps running on top of iOS.

Phone, Messages, Camera, Maps, Banking, Shopping, Email, Safari, and Games are all apps.

iPhone
   |
   +-- iOS
          |
          +-- Phone
          +-- Messages
          +-- Camera
          +-- Maps
          +-- Safari
          +-- Thousands Of Other Apps

Safari Is An iPhone App

Safari is Apple's main browser app on iPhone.

Chrome, Firefox, Edge, Brave, and other browsers also exist on iPhone, but they still use Apple's required iOS browser engine.

iOS
   |
   +-- Safari
   +-- Chrome
   +-- Firefox
   +-- Edge
          |
          +-- HTML
          +-- CSS
          +-- JavaScript

iPhone Browsers Run HTML Apps

Browser apps on iPhone can load and run HTML, CSS, and JavaScript applications designed for small screens.

A mobile-friendly website can behave very much like a traditional app.

One Web App
      |
      +-- iPhone Safari
      +-- iPhone Chrome
      +-- iPad
      +-- Desktop Browser

Inspector Can Simulate iPhone Screens

On Windows 11, Chrome and Edge include Developer Tools.

Inside Inspector there is a Responsive Design Mode that can simulate many phone and tablet screen sizes, including iPhone-like screen sizes.

F12
 |
 +-- Inspector
        |
        +-- Responsive Design Mode
                |
                +-- iPhone Sizes
                +-- Android Phones
                +-- Tablets
                +-- Custom Sizes

This lets a developer working on Windows see how a website may appear on iPhone-sized screens.