The storage of large amounts of information will, for the foreseeable future, consist of storage on a surface. At present, magnetic surfaces are most widely used, although silver halide surfaces are also finding some limited application where the non-erasability is not a serious limitation. Other media now in the laboratory will undoubtedly find practical use. The problem facing the large memory designer is one of choosing a suitable medium and determining a way of breaking up this surface to make it accessible.