A self-aligned, nonvolatile memory structure based upon phase change materials, including chalcogenides, can be made with a very small area on an integrated circuit. Accordingly, it is possible to record an information signal having a large amount of information in the recording medium without lowering a recording speed and it is also possible to easily reduce the size, weight and cost of the apparatus. The neural networks are determined iteratively to adjust to the values of a learning base with predetermined tables connecting various values obtained for the output data to the corresponding values of the input data.