This article explains how to prevent programs from appearing before other programs in Windows.
How do you prevent new windows from stealing focus?
If you have ever been annoyed by a program popping up without your permission for the task you were doing, even though you haven't selected anything, then you have become a victim of an attention stealing program.
Focus stealing is sometimes due to malicious programming by the software developer doing it. However, most of the time it is simply buggy software or operating system behavior that you need to pin down and try to fix or avoid.
Ideally, no program other than the one you are currently working with will accept mouse or keyboard input. Furthermore, the window will remain on top of all other windows that you are not currently using.