IOS adapts to various iphone screen sizes

With the increase in Apple products and the increasing number of screen sizes, how do we make our app adapt to different types of apple screen sizes when writing programs?

When Apple gave a solution, a point concept was proposed. A point in 3gs corresponds to one pixel, and a point in 4 (s) corresponds to two pixels. In iOS development, it is more convenient to point as a unit, as @1x in the following table is a point corresponding to a pixel, @2x is a point corresponding to two pixels, and so on. The number of pixels per inch that becomes the PPI. Because the text and color are vector data, the pixels will not be distorted after zooming in, but when the picture will be distorted, so we need to design the app in different sizes of images (one times, twice times the graph, etc.), to ensure that the app's picture without losing its true.

Equipment	Diagonal size	Logical resolution	Scale factor	Device resolution
3GS	3.5	320*480	@1x	320*480
4 (S)	3.5	320*480	@2x	640*960
5 (S)	4	320*568	@2x	640*1136
6	4.7	375*667	@2x	750*1334
6Plus	5.5	414*736	@3x	1080*1920

IOS adapts to various iphone screen sizes