Get problem to understand "Topological Structural Analysis of Digitized Binary Images by Border Following" Suzuki Abe
In the paper 4-(8-) refers to the 4 and 8 neighbor connectivity between the two pixels and in the algorithm NBD is the newest border found during the raster scan of the binary image and LNBD refers to the last newest border, NBD and LNBD is stored to obtain the surroundness relation between the borders.