1. In a data processing system having a memory for storing and reading data words having parity bits associated therewith, an arithmetic unit for processing the data words in programmably selected formats, and a control section for causing execution of program instructions, some of which specify reformatting of the data words, and for providing control signals indicative of programmably selected data formats, a programmable data reformat system comprising: control signal receiving means for receiving program control signals for specifying one of a plurality of data reformatting operations programmably specified by operative instructions, wherein said control signal receiving means includes instruction receiving means for receiving instruction field signals for designating the field of data signals to be extracted for reformatting, control mode receiving means for receiving control mode signals for selecting between predetermined reformatting of predetermined fields of said data signals and one of two possible floating point formats, data mode receiving means for receiving data mode signals for selecting between normal data output, unconditional complement output, and complement output dependent upon predetermined signal conditions, shift enable receiving means for receiving shift enable signals for selecting predetermined unique positioning of predetermined fields of said data signals, and clock signal means for enabling selection of the sign of said reformatted ones of data signals, and for controlling manipulation of said data signals in double precision floating-point operations; data signal receiving means for receiving data signals to be programmably reformatted in a manner specified by said control signals; parity signal receiving means for receiving parity signals associated with said data signals; reformat means coupled to said control signal receiving means and to said data signal receiving means for reformatting selected ones of said data signals in said one of a plurality of data reformatting operations programmably predetermined in response to received ones of said control signals; and parity means coupled to said parity signal receiving means and said control signal receiving means for adjusting parity during reformatting and providing output parity signals indicative of the parity of the reformatted ones of said data signals.