Abstract: A data processor uses storage units that are subdivisible into predetermined fields for executing instructions that cause the data processor to handle numbers from respective ones of the fields separately. The processor has an instruction that addresses a first and a second one of the storage units. In response the data processor takes a first and second group of successive bits from a first and second one of the fields of the first one of the storage units, places the first and second groups of successive bits at respective shifted positions both in the same field in a result storage unit, a bit position distance between the shifted positions being controlled by a content of the second one of the storage units.