The catalogue files are plain text files.  The catalogue file
unlabelled-<N>.cats contains representatives of the isomorphism
classes of unlabelled lattices with N elements, with each line
encoding one lattice.  Lines are terminated with '\n' = 0x0a.

Each line of a file encodes one lattice as follows:
 - The elements of the lattice are labelled 1,..,N ; where 1 is
   the upper bound and N is the lower bound of the lattice.
 - The chosen representatives are levellised, that is, if one
   has A covers B (where 1 \le A,B \le N), then A < B holds.
   Thus, the incidence matrix describing the covering relation
   is upper triangular.
 - The line encoding a lattice gives the incidence matrix for
   the covering relation of the lattice in column major order:
      For 1 \le A < B \le N, the ((B-1)*(B-2)/2+A)-th character
   of the line indicates whether A covers B:  the character is
   '1' if A covers B; the character is '.' otherwise.

Please cite the following paper when using data from this
catalogue:
  V. Gebhardt, S. Tawn:  Constructing unlabelled lattices,
  Journal of Algebra, to appear (2019).