1. A method of operating an electronic data processing system so as to permit a single bit-field instruction to cause access of variable length bit fields in a storage of said system without requiring any special relation between the boundaries of addressable elements within said storage and the beginning and end of the bit fields, comprising the steps of: initializing a base register RB of said system to contain a base address of an addressable element; initializing a displacement register R7 to contain (1) the element displacement, from said base address, of the addressable element containing the first bit of a desired bit field, and (2) the bit displacement, from a boundary of the last recited addressable element, of said first bit; reading into an instruction register of said system a bitfield instruction which contains (1) an operation code identifying it as a load instruction or a store instruction for causing access of a bit field, (2) an identification of which register in said system shall be used as RB, (3) an identification of another register R in said system which is to be used as the destination of a bit field to be loaded into R from storage or the source of a bit field to be stored from R into storage and (4) a number L indicating the number of bits in said particular bit field; adding said element displacement to the contents of register RB; concatenating said bit displacement to the result of said addition, thereby providing an indication of the location in storage of said first bit; and beginning with said first bit, either loading said number of bits into R from storage or storing said number of bits from R into storage depending upon whether said bit-field instruction is a load instruction or a store instruction, respectively.