1. A cyclically operable microprogram control system for use in an information handling system for generating subcommand signals for controlling systems operations required for processing program instructions, each program instruction including an operation code, said microprogram control system comprising: a first store for storing address words, each including a plurality of addresses; a second store for storing standard sequences of microinstruction words and execution sequences of microinstruction words; each of said first and second stores including addressing means and output register means for providing access to said store contents and storage for said address and microinstruction words read from said first and second stores respectively; and, selection means coupled to said output register means of said first and said addressing means of said second stores, said selection means receiving said plurality addresses of an address word read out from said first store in response to said operation code during the processing of said program instruction, said selection means applying selectively each of said plurality of addresses to said addressing means of said second control store for accessing microinstructions of said standard and execution sequences respectively for generating said signals during first and second phases of operation required for processing said program instruction.