shift instruction

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shift instruction An instruction specifying that the contents of a shiftable register (occasionally concatenated registers) are to be shifted either to the left or to the right a specified number of register positions. Shifts can be circular or they can be open at both ends. In the latter case there is usually a specification of what happens to bits being shifted out of the register (often they are discarded) and what bits are to be shifted into the register (most often 0s).