APPARATUS FOR CONTEXT SWITCHING OF INPUT/OUTPUT DEVICES IN RESPONSES TO COMMANDS FROM UNPRIVILEGED APPLICATION PROGRAMS

Hardware input/output control apparatus for use in a computer system which control apparatus is joined to a plurality of input/output devices, and includes circuitry which responds to commands from unprivileged application programs addressed to input/output devices joined to the hardware input/output apparatus for selecting a context to be placed on an addressed input/output device to function with an application program sending the command. Context switching is effected in response to commands from unprivileged application programs without involving the operating system or trusted code.