1. A non-volatile memory device, said memory device including: a matrix of memory cells, each memory cell being individually programmable to at least one first logic level and individually erasable to a second logic level, partition means for logically subdividing the matrix into a plurality of subspaces, each subspace comprising at least one respective memory cell, selection means for selecting a subspace, operative means for performing an operation on all the memory cells of the selected subspace, and means for dynamically modifying the number of subspaces and/or the number of memory cells included in each subspace.