  We develop a behavioral theory for the untyped call-by-value lambda calculus
extended with the delimited-control operators shift and reset. For this
calculus, we discuss the possible observable behaviors and we define an
applicative bisimilarity that characterizes contextual equivalence. We then
compare the applicative bisimilarity and the CPS equivalence, a relation on
terms often used in studies of control operators. In the process, we illustrate
how bisimilarity can be used to prove equivalence of terms with
delimited-control effects.
