One of the most consistent criticisms of Apple's iOS, the operating system used by the iPhone and iPad, is its limited ability to organize documents and data. Until now, documents created on a mobile device have been saved to an app's file space, and opening a document generally involved reopening the app — usually with no easy way to sort and organize the files.
The idea behind that process — sandboxing — was to isolate app data from other apps and the operating system, and so limit the potential for security breaches. But the sandboxed nature of iOS apps meant documents could only be saved to, and then accessed from, the apps that created them. Apple over time added ways of sharing data between apps and to contacts, making it easier to share documents first via email and text message and more recently by using online services such as DropBox and OneDrive.