1. In a computer system having first and second electronic memory means which together are used to store a program comprising executable instructions, a method of protecting against unauthorized duplication of selected proprietary portions of said program, the method comprising the steps of: pre-storing in said first memory means prior to distribution to a system user said selected proprietary portions of said executable program, whereby said selected proprietary portions of said program are not readily susceptible to access and duplication by a system user; pre-storing prior to distribution to a system user the remaining portion of said executable program on an external storage medium, said external storage medium being available for access and use by system users; and when running said executable program in its entirety on said computer system, said computer system automatically performing the steps of: (a) loading said remaining portion of the executable program from said external storage medium to said second memory means; (b) commencing with execution, in turn, of each instruction contained in said second storage means until instructed to transfer to said first storage means; (c) thereafter executing, in turn, the selected proprietary portions of said program stored in said first memory means; (d) thereafter returning to said second memory means and continuing with execution of said remaining portions of the program; and (e) repeating steps (a)-(d) until said program is completely executed.