1. In a digital data processing system having an instruction repertoire including a plurality of macro instructions which can be programmed and executed in desired sequences, and each macro instruction execution is under the control of one or more pre-stored micro instructions, each of said pre-stored micro instructions for controlling a predetermined portion of the execution of the macro instruction, macro instruction overlap control apparatus comprising: first and second control store means, each adapted for storing the sequences of micro instructions for controlling the execution of the repertoire of macro instructions; macro instruction execution overlap control means coupled to said first and second control store means for controlling the overlap of execution of sequentially received macro instructions; and micro instruction execute means coupled to said first and second control store means and said macro instruction execution overlap control means for combining micro code instructions for simultaneous execution to effect overlap of execution of associated macro instructions.