Adapter for coupling a legacy operating system to a driver of an I/O channel which has an incompatible native operating system interface

An adapter program in a program storage memory that is readable by a computer, for coupling a legacy operating system to a driver program of an I/O channel, where said driver program has an interface to a native operating system which is incompatible with said legacy operating system and where said native operating system includes a full set of native support routines which perform tasks for said driver program when called by said driver program;

• said adapter program including a translator which receives a legacy control structure from said legacy operating system, that represents a legacy I/O instruction, and generates a different control structure in response;
• said adapter program also including an emulator having a) an interface to said driver program which is bi-directional, and b) simulated support routines which simulate only a small subset of said native support routines in said full set;
• and,
• said emulator further including steps for performing said I/O instruction by a) calling an external routine in said driver program thru said bi-directional interface in response to said different control structure, b) receiving a call back from said driver program thru said bi-directional interface as a response to said calling of said external routine which identifies one native support routine in said small subset, and c) immediately executing a simulated support routine which simulates said one native support routine, without sending any result to said native operating system, in response to said call back from said driver program.