Abstract: A method of executing a program module in an expanded memory of a computer system using PC or MS DOS. The program module is divided into a resident section and a transient section. After loading the module into main memory, the program module relocates the transient section to expanded memory. The module is called, either directly or via an interrupt, through an entry point in the resident section, while the majority of the program module function is performed by the code in the transient section. The module is also divided into a third, data, section which can be shared by the resident and transient sections, and which can be loaded either into expanded or main memory.