Protection Against Reloading an Active Resident Program
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
This article describes a method of preventing multiple copies of a program from being loaded even when the primary entry point of the program may have been redirected. IBM Personal Computer Disk Operating System (DOS) has provided a convenient way of making programs become a resident part of the DOS. The is useful for programs such as printer drivers so that programs will not be disturbed by programs loaded later and can continue to print. However, the ability to stay resident also opens up the possibility that multiple copies of the program may become resident which not only uses up memory needlessly but may cause conflicts between the copies trying to communicate with the same printer. The program, therefore, needs to be able to recognize that a copy of itself already exists in memory.