iPhone 4s

Location Services is the master list of every app that can use your position, and the level of access each one has.

The setting exists, but we have not recorded its exact location on iOS 9 yet.

Background App Refresh lets apps fetch new content while they are closed, which keeps them current at the cost of battery and data.

Settings > General > Background App Refresh

One slider changes text size across the system and every app that uses Dynamic Type, and Accessibility offers larger sizes still.

The setting exists, but we have not recorded its exact location on iOS 9 yet.

Each app has its own notification switch, plus separate control over the Lock Screen, banners, notification centre, sounds and badges.

The setting exists, but we have not recorded its exact location on iOS 9 yet.

Find My lets you locate your iPhone on a map, play a sound on it, mark it as lost, or erase it remotely, and it also enables Activation Lock.

The setting exists, but we have not recorded its exact location on iOS 9 yet.

Low Power Mode cuts background activity and visual effects to stretch the charge you have left, and turns the battery icon yellow while it is on.

Settings > Battery > Low Power Mode

Your passcode is the root of iPhone security: it encrypts your data, and Face ID or Touch ID are conveniences layered on top of it.

The setting exists, but we have not recorded its exact location on iOS 9 yet.

The Software Update screen shows which iOS version you have, offers any update that is available, and holds the automatic update settings.

Settings > General > Software Update