1. A digital computer for executing sequential instructions I.sub.1, I.sub.2,. .. I.sub.N of a single program in a time-multiplexed fashion, said digital computer being comprised of: a memory means in which each of said sequential instructions is represented by respective first, second, and third sets of microcommands and where said first set of microcommands for any particular one of said sequential instructions must be executed before said second set of microcommands for that same instruction which in turn must be executed before said third set of microcommands for that same instruction; means for reading from said memory means the third set of microcommands for instruction I.sub.i-3, the second set of microcommands for instruction I.sub.i-2, and the first set of microcommands for instruction I.sub.i-1, where i is an integer; and a control means for executing said third set of microcommands for instruction I.sub.i-3, subsequently executing said second set of microcommands for instruction I.sub.i-2, and subsequently executing said first set of microcommands for instruction I.sub.i-1 ; said means for reading and said means for executing including means for performing their respective operations in a repetitive fashion with the subscript i being incremented each time by 1.