Continuations occur in many areas of computer science: logic, proof theory, formal semantics, programming-language design and implementation, and programming. Like the wheel, continuations have been discovered and rediscovered many times, independently. In programming languages, they represent of “the rest of a computation” as a function, and proved particularly convenient to formalize control structures (sequence, gotos, exceptions, coroutines, backtracking, resumptions, etc.) and to reason about them. In the lambda-calculus, terms can be transformed into “continuation-passing style” (CPS), and the corresponding transformation over types can be interpreted as a double-negation translation via the Curry-Howard isomorphism. In the computational lambda-calculus, they can simulate monads. In programming, they provide functional accumulators.