A method of reducing the memory required for decompression of a compressed frame by storing frames in a compressed format using DCT compression and decoders for implementing such a method are disclosed. The housing has an inlet, an outlet and a trap aperture. Personal content for each user, such as digital file usage, is indexed in association with each physical context. The method entails encoding and decoding each picture in said stream of pictures in either frame mode or in field mode. , the original map is continuously displayed while only the particular area is replaced by the detailed map. A corresponding virtual storage system is also provided.