Abstract: The invented data compression/decompression methods, device, and resulting data structures, operate by noting likenesses and differences between portions of data, and effecting data storage only with respect to the noted differences. The compression method arranges the data, compares portions of the data, and provides a flag to signal changes between adjacent data portions. The decompression method reads a portion of data, identifies whether the flag signals any changes in the data, and if so, reads a subsequent portion of data; but if no changes are signaled, then the first portion of data is duplicated. The invented device includes memory, a structure for storing data in the memory, data stored in the memory with flags to signal changes in the data, and structure for accessing and using the stored data. The invented data structure includes data divided into predetermined sections, and flags associated with the sections to signal changes within the sections.