1. An input-output arrangement for a data processing system including a main store and at least one device controller, said arrangement comprising: (a) at least one input-output bus connected to said device controller; (b) a processor for controlling said input-output bus; (c) first connecting means separate from said input-output bus for connecting said processor to said main store; (d) second connecting means for connecting said processor to said input-output bus; (e) a direct memory access controller; (f) third connecting means for connecting said direct memory access controller to said main store; (g) fourth connecting means for connecting said direct memory access controller to said input-output bus; and (h) fifth connecting means separate from said input-output bus for connecting said direct memory access controller to said device controller; (i) said first, second and fourth connecting means enabling said processor to initiate transfer of information through said direct memory access controller while itself simultaneously participating in information transfer and maintaining control over said direct memory access controller, said first, second, third, fourth and fifth connecting means allowing parallel transfers of information between said processor and said main store, between said direct memory access controller and said main store, between said processor and said device controller and between said direct memory access controller and said device controller.