The Free On-line Dictionary of Computing (30 December 2018):

continuation passing style
continuation
continuations

    (CPS) A style of programming in which every user
   function f takes an extra argument c known as a "continuation".
   Whenever f would normally return a result r to its caller, it
   instead returns the result of applying the continuation to r.  The
   continuation thus represents the whole of the rest of the
   computation.  Some examples:

    normal (direct style)		continuation passing style

    square x = x * x			square x k = k (x * x)

    g (square 23)				square 23 g

    (square 3) + 1				square 3 ( \ s . s + 1 )

   (1995-04-04)