It is the aim of this paper to present a uniform generalization of both the Myhill/Shepherdson and the Kreisel/Lacombe/Shoenfield theorems on effective operators. To this end we consider countable topological T o-spaces that satisfy certain effectivity requirements which can be verified for both the set of all partial recursive functions and for the set of all total recursive functions, and we show that under appropriate further conditions all effective operators between such spaces are effectively continuous. From this general result we derive the above mentioned theorems and also the generalizations of these theorems which are due to Weihrauch, Moschovakis and Ceitin. There is a long history of interest in continuity theorems in recursive function theory, and such continuity results are basic in computer science when studying continuous partial orders introduced by Scott and by Eršov for studies of the semantics of the λ-calculus.