1. A method of making an electronic matrix array comprising the steps of: forming at least one layer of phase changeable material on a substrate, said phase changeable material having a substantially nonconductive state and a comparatively high conductive state, said layer being formed in one of said states; parallel programming said layer by irradiating selected areas of said layer to simultaneously convert said selected areas of said layer to the other one of said states to form selected substantially nonconductive portions of said layer and selected comparatively high conductive portions of said layer; forming first and second sets of electrically conductive address lines on respective opposite sides of said layer, said address lines of said first and second sets being formed for crossing at an angle to form a plurality of crossover points; and said selected substantially nonconductive layer portions and said selected comparatively high conductive layer portions being formed between said first and second sets of address lines.