bits manipulation (C)

I'm an autodidact and I have programmed in C for one year now, but never studied this topic. Apart from operating systems or embedded systems, when do we need to manipulate bits in 21st century ? If you could give some examples...

>>13
"Keep in mind that I was being rather sarcastic"
Yes, this is what I discovered when I took a look at the source code. At the same time, I was still searching and discovered this : http://www.eskimo.com/~scs/cclass/krnotes/sx5i.html
but it remains a little obscure to me. I know that no one will take the time to explain it and give some examples, and I understand that, so if anyone has a good link or book that explains this concept clearly, I would be really glad.