Three programmers come to a one-way street. The computer scientist looks left, sees there's no cars coming, and crosses. The professional programmer looks lef

Three programmers come to a one-way street. The computer scientist looks left, sees there's no cars coming, and crosses. The professional programmer looks left, then looks right -- just in case! -- before crossing the street. The distributed systems programmer looks left, then looks right, then looks up to make sure there aren't any planes falling out of the sky...