Air jet texturing converts a bundle of filaments into a yarn with projected arcs and loops that entangle with the core fibers. An object oriented software program calculates the effects of overfeed, air pressure, and texturing speed on the bulk and instability properties of air jet textured yarns. The program generates data regarding physical yarn bulk, instability at various bulk levels, bulk range, air pressure, and texturing speed. Forward selection procedures establish coefficients of overfeed, air pressure, texturing speed, and the interactions of air pressure and texturing speed, as well as minimum and maximum overfeed, air pressure, and texturing speed. Nested loops calculate the instability and physical bulk for each combination of overfeed, air pressure, and texturing speed. 3 refs.