= R =
register dancing n.
Many older processor architectures
suffer from a serious shortage of general-purpose registers. This
is especially a problem for compiler-writers, because their
generated code needs places to store temporaries for things like
intermediate values in expression evaluation. Some designs with
this problem, like the Intel 80x86, do have a handful of
special-purpose registers that can be pressed into service,
providing suitable care is taken to avoid unpleasant side effects
on the state of the processor: while the special-purpose register
is being used to hold an intermediate value, a delicate minuet is
required in which the previous value of the register is saved and
then restored just before the official function (and value) of the
special-purpose register is again needed.
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.