Abstract: A computer system, including a processor, an input device and an output device and that executes an operating system to support the execution, is used to execute first and second sets of application programs. The operating system includes a graphical user interface coupleable through an output driver to the output device and an input interface including an input queue coupleable through an input driver to the input device. 1An environment manager program is also executed by the processor. This program includes a third list of a second set of application programs and a fourth list of application program windows corresponding to the second list of application programs. Execution of the environment manager program provides for the inclusion of the environment manager program in the first and second sets and for selectively swapping with the operating system the first and third lists and the second and fourth lists to switch between the execution of the first and second sets of application programs.