I've searched a lot but find nothing about frame and dimension. I thought this should be a big topic.

Anyway, when create a view using frame, the whole screen size is 320\*460 (320\*480), but the dimensions of screen is 720\*960. Can someone explain this? How to convert them.

This is only for 3.5 inch non-retina device.

EDIT:
I figured it out. The problem is because the size of iPad and iPhone is different. For iPhone, the dimension is 4:3, but for iPad, the dimension is 1.33.