Introduction to IOS

1. Preface

I am about to learn about Ios. First, I want to know about it. Of course, the essential knowledge before learning IOS is still needed: Objective-C programming language, IOS system itself, and iPhone, iPad and itouch features to understand the appearance of IOS interfaces and iPhone and iPad applications. Know yourself and know what you want ~

2. iOS introduction 2.1 only one application is running

Only one application can be activated and displayed on the screen during each period of time.

2.2 only one window exists

Only one window can be operated by the application

2.3 restricted access

Users can only read and write files in the file system that iOS creates for the application. This area becomes a sandbox.

2.4 limited response time

If you press the Home button, IOS will return to the home screen. You need to save everything and release it quickly. If the application is not saved within 5 seconds and the control is abandoned, the application is terminated, regardless of whether the user has saved the application.

2.5 limited screen size

The screen size is limited, so only limited controls can be placed. For example, the iPhone 4 Retina display is only 640*960 pixels, while the iPad 2 is only 1024*768 pixels larger.

2.6 limited system resources

The memory size of applications is limited by the amount of physical memory not used in mobile phones.

2.7 garbage collection is not supported

Cocoa touch does not support garbage collection, but the objective-C version supported by iOS 5 introduces a feature-automatic reference counting (ARC ), with this feature, you do not need to manually manage the memory for objective-C objects.

2.8 New Features

Core location determines the current geographic coordinates of the mobile phone. It provides built-in cameras and photo libraries, and the SDK allows applications to access both. The built-in accelerator is used to detect grip and movement modes.

3. Conclusion

This article briefly introduces the features of iOS, hoping to provide some help for the beginner's shoes!