I wonder how people who have not seen the obfuscated C contest entry »Pi« (http://www.cise.ufl.edu/~manuel/obfuscate/pi.c) solve this. Googling? Guessing? Actually trying to make sense of the code?
I recognized it immediately because I know of the IOCCC. But I think even if you don't, you could always grab a C compiler and just run the program (and remove the warnings ). The result of 3.156 together with looking at the source code reveals the answer pretty quickly.
Yes, I have decided to run it on online c interpretter and 3.156 was not accepted so I read the challenge forum and answered pi. I have not looked at expanded code till now ... OK each "disk pixel" decrements F, but OO is decremented only on the line start otherwise -F>0 is evaluated to true so OO is not decremented. Therefore F/OO/OO is disk to square ratio ...