What is meaning of decimal part of CGPoint?

Question

I saved an array of points that are being touched during finger moving on image view. When I look into points set, they look like below:

{144, 326.5}
{144, 324.5}
{144, 324}
{144, 324.5}
{144, 324}
{144, 323.5}
{144, 324}
{144, 323.5}
{143, 322},...

I want to know what is the meaning of decimal part in these CGPoints. I also should mention that my target device is iPhone within retina 4-inch screen size.

Answer 1

the deicmal part means: half a point. ... so 1 pixel in retina

in retina you have a scalefactor of 2 so two pixels = 1 point