Fred Brooks is a legend for his time at IBM and his book, The Mythical Man-Month, which became a Bible for software developers. The book identified the key concept that "you can't always speed up an overdue software project by adding more programmers; beyond a certain point, doing so increases delays," as Wired's Kevin Kelly explains in a new interview with Brooks.

Brooks, a University of North Carolina computer scientist, has a new book out, The Design of Design, in which he takes on a host of new fields. Across of all of them, he singles out one crosscutting idea: know your limiting factor.

The critical thing about the design process is to identify your scarcest resource. Despite what you may think, that very often is not money. For example, in a NASA moon shot, money is abundant but lightness is scarce; every ounce of weight requires tons of material below. On the design of a beach vacation home, the limitation may be your ocean-front footage. You have to make sure your whole team understands what scarce resource you're optimizing.

There is one other great moment in Kelly's interview with Brooks in which the latter reveals that someone (a real person! who is still alive!) had to make the decision to enable the use of lower-case letters in computing.

Kelly: What do you consider your greatest technological achievement?
Brooks: The most important single decision I ever made was to change the IBM 360 series from a 6-bit byte to an 8-bit byte, thereby enabling the use of lowercase letters. That change propagated everywhere.