Beginning with Grzegorczyk’s important concepts of hierarchies of recursive functions, computable functionals, and computable real-valued continuous functions [1], the author gives a well-written and comprehensive exposition of the basic notion of relative computability for continuous real-valued functions. Considerable attention is given to ideas of degrees of recursive unsolvability of formal operations leading from the computable toward the noncomputable. Indeed, this effort mainly addresses open question 2 given in the addendum of Pour-El and Richards [2]. Although Myhill [3] has given a recursive function defined on a compact interval and having a continuous derivative that is not recursive, the author shows that the derivative is semicomputable.