Block relationship files are tabular files, they do not depict the actual spatial relationships between census blocks. Areal relationships between blocks can be determined by using commercially available GIS software and publicly available versions of the Census Bureauís TIGER/Line files.
These block relationship files identify states and counties by FIPS (Federal Information Processing Standards) codes. These files do not include the geographic names referenced by the FIPS codes. Block relationship files are provided in a comma-delimited ASCII text file format. Each type of block relationship file has a separate record layout. The record layout for each type of relationship file can be found on the 2000 Census Block Relationship File Record Layout Page.