Pratical Applications of Bit Manipulation?

I have seen many interview questions with interesting bit manipulation solutions. Can someone tell me the pratical applications of such problems?

Pratical Applications of Bit Manipulation?

one application is suppose you need to implement some mathematical manipulation in an application in the operating system of ur cell phone. there u can't not to use bit manipulation as u hav very less memory with u. and also in DSP while designing a operating system which is not equal to general 32 bit system u need bit manipulation. there are numereous applications.