A memory management method is provided to manage a memory in which areas of a garbage collected Java heap memory and a non-garbage collected external heap memory can be secured, by using a program executed by a processor in a computer. The system also includes an annotation lifter that extracts the handwritten annotation from the electronic image and converts the handwritten annotation into a computer-usable form. In the multifunctional digitizer module, a digitizer sensor board senses position of a position pointer or finger contact on a surface and a shield film is integrated on one surface of the digitizer sensor board by semiconductor process to screen out external noise. Furthermore, interactive systems and physical objects may be used to reinforce associations between imagery and the functional aspect of a concept. A synchronization program running on the central application server downloads updated copies of files from the local file servers, and uploads the updated copies of files to the central file server as latest editions of the files.