We present an abstract machine and a reduction semantics for
the

-calculus extended with control operators that give access to
delimited continuations in the CPS hierarchy. The abstract machine is derived
from an evaluator in continuation-passing style (CPS); the reduction
semantics (i.e., a small-step operational semantics with an explicit
representation of evaluation contexts) is constructed from the abstract
machine; and the control operators are the shift and reset family. At level

of the CPS hierarchy, programs can use the control operators shift

and reset

for

, the evaluator has

layers of
continuations, the abstract machine has

layers of control stacks, and
the reduction semantics has

layers of evaluation contexts.
We
also present new applications of delimited continuations in the CPS
hierarchy: finding list prefixes and normalization by evaluation for a
hierarchical language of units and products