Abstract: A method for interfacing an application program with an operating system of a computer when the application program relies on a predetermined address line to be set in a low state during the initial stages of the application program's operation. The computer has a lower memory region, which is addressable when the predetermined address line is in a low state, and an upper memory region, which is addressable when the predetermined address line is in a high state. The method provides an operating system stub in the lower memory region of the computer and provides an operating system in the higher memory region of the computer. The stub receives each operating system call made by the application program. After receiving an operating system call, the operating system stub sets the predetermined address line to the high state if the predetermined address line is in the low state then invokes the operating system call.

Abstract: A method for interfacing an operating system extension with a personal computer includes the step of providing a function command to the operating system of the personal computer when the operating system extension performs a function typically performed by the operating system of the personal computer. The operating system of the personal computer responds to the function command to perform functions unique to the operating system of the personal computer so that the application program will execute properly. As an example, when an application program is being loaded by an operating system extension, the operating system of the personal computer responds to the function command by revising the application program so that the application program will be compatible with the personal computer.

Abstract: A program is stored in the memory of a computer to create an image of the program. The image of the program is examined for information indicating whether the program is compatible with the configuration of the computer. If necessary, the image of the program is revised so that the program will operate properly with the configuration of the computer. In a first embodiment of the invention, information identifying a configuration of a computer system with which the program is compatible is associated with the image of the program. In a second embodiment of the invention, a predetermined set of instructions and data are replaced with alternate instructions and data.