Do people in prison know what each other is in for?

I’ve heard that in prison culture, child molesters and rapists are the lowest of the low and even looked down upon by the serial killers, mob bosses and cannibals. (“Yeah I eat people, but at least I don’t touch children!”) It makes me wonder how readily available this information is. I would think that’s probably something you’d wanna keep to yourself, or is there some kind of unwritten law that demands you disclose your reason for being in prison, otherwise we’ll beat you everyday…Anyone know?