Current user in header section of the project

Current user in header section of the project

Dear Sirs,
I want to show the current logged user in header screen of my project.
As far as I can understand this is only possible if the screen is from Login type.
Is that true? Is the any other approach?
If the screen is from type Login, what is the difference between Control elements "Current user" (ID:10001) and "Display - current user" (ID:10002) because just the second one work for me (meaning shows the current user)?
Regards,
Yolov

This is a migrated post! Originally posted on 25.06.2013 by user yolovs. Please be aware that information can be outdated.