"values of β may give rise to dom!" By Mark Allen In what may be the strangest error message of all time, we are warned that values of beta may give rise to dom! This bizarre error message made it into early UNIX releases. Why? What caused it? What is β? How can we stop the insidious rise of dom?! UNIX publicly debuted in 1974 in an article in the Communications of the ACM, and it has thrived and prospered ever since. In this talk, we will take a whirlwind tour through the error handling subsystems of an early UNIX kernel and its utilities, with an eye toward what those techniques tell us about system design.