A method of protecting application program software includes steps of (a) actuating a tracer function to copy 2.sup.1 to n instructions from the API code; (b) storing and executing the instructions; and (c) returning to the next instruction (2.sup.(1 to n)+1) of the API code, where 2.sup.1 to n represents the number of instructions and n is the maximum number of instructions describing the API code.