The Binary Assignment Map (BAM) is a highly compressed file format for storing genomic sequence data, the need for which was prompted by exponential decreases in sequencing time and cost following the 2003 completion of the Human Genome Project.   BAM files store nucleotide values tagged with metadata including nucleic acid fragment of origin and genomic reference site assignment as well as scores for raw data quality and assignment confidence.  A binary archive of the human-readable ASCII is then constructed and indexed enabling portions of the alignment map to be selectively expanded in computer memory as needed.