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. [Jargon File]