1. An environment manager providing for the controlled execution of respective application programs in primary and alternate application execution environments within a computer system operating under the control of an operating system including a primary input queue and a primary output routine, said environment manager comprising: a) an alternate input queue for storing input data for applications executing in the alternate application environment; b) an alternate output routine for managing the processing of output data provided by applications executing in said alternate application environment; and c) a control routine coupled to said operating system to selectively provide for the concurrent use of said primary input queue and said primary output routine or of said alternate input queue and said alternate output routine, said control routine further providing for the transfer of the output data processed by said alternate output routine to said primary output routine.