Question about Flags (general)

[Cyhawk]

Hey all, my question involves flags. As i understand it, diku dirvs use 
letter flags to represent numbers (like PLR_ flags) and i know theyre 
powers of two ths allowing for easy addition of more 'flags' to the 
equasion.. I also noticed the max you can use is dd (30 letters) 
(1073741824) without causing issues. My question is, what determines the 
max number you can use? Is it complier controled, CPU architechture 
controled? Just curious on how the thing works more indepth =)

-Thri