What are you talking about?
IP? IP has 32 bit (ex:192.168.123.123) but I think the first 3 digits (ex: 10.0.0.0) are called "Class A" (I'm not sure about that, if the class A is the first 3 ones or the next 3...).
You probably know that IP 4 number are between 0 and 255. So you need 8 bit to count this number (2^8 = 256) because computer only use 1 or 0 of course
