Detailed information about the screen size, resolution, and length ratio of iOS devices

According to the screen size and resolution, IOS currently has six versions.
1, 3gs; 2, 4S: Representative; 3, iphone5; 4, ipad2: Representative; 5, ipad4: Representative; 6, iPad Mini.
Only when the resolution is different, such as the first, second, or fourth, the development can provide two kinds of resolution, automatically recognized by the application?
It's just the case that the sizes are different. For example, when compared to the 4th and 6th, there is no impact on development?

The resolution and size are different, such as the ratio of two to three phases?

IOS
The current resolution of the device is as follows:
IPhone/iPod Touch
IPhone 1, 3G, 3 GS, iPod Touch 1, 2, and 3
Retina screen 640 pixels x 960 pixels iPhone 4, 4 s, iPod Touch 4
Retina screen 640 pixels x 1136 pixels iPhone 5, iPod Touch 5

IPad
Ordinary screen 768 pixels x 1024 pixels iPad 1, ipad2, iPad Mini
Retina screen 1536 pixels x 2048 pixels new iPad, iPad 4

Question 1: The resolution is different. For example, if the resolution is one to two, or four to four, two types of resolution can be provided during development. Will the application automatically recognize the resolution?
A: In
Before the iPhone 5 and iPod Touch 5 are available, the first and second problems for developers are the difference in resolution, because they are all 3.5-inch screens. In addition, if you are careful, you will notice that their resolution is exponentially related.
This provides convenience for iOS design and development. You only need to design a set of interface design, and then perform proportional scaling.

To facilitate developers, point is used in IOS to describe the size of interface elements.
So for the first and second, you only need to regard the screen size as 320
X 480 points for development. The Conversion Relationship between points and pixels is as follows:
1 point = 1 pixel
Retina screen 1 point = 2 pixels
The same is true for iPad development.
X 1136.

On iPhone 5 and iPod Touch 5, for developers, the interface size is 320.
At X, you only need to adjust your interface according to the size (if necessary ).
For example, if I have a button to place it in the middle of the screen, you only need to set its center to (320, 480) on a device with a page size of 320/2x480/2) the system button on the Retina screen at can be correctly displayed in the middle;
On a device with a screen size of 320x568, you can set its center to (320/2, 568/2 ).
Directly use [uiscreen
Mainscreen] bounds] can obtain the basic resolution of the current screen, so no hard code is needed.

Question 2: Is there any difference in size, for example, when compared to the 4th and 6th, there is no impact on development?
A: You only need to pay attention to the resolution during development, iPad
2. The screen size of the iPad Mini is different from that of the iPad Mini, but the resolution is the same, so there is no impact at all. Apps running normally on the iPad 2 can also run normally on the iPad Mini.

Question 3: What is the difference in resolution and size, such as the ratio of two to three phases?
A: In
I have answered the question