The text file chr_NC_gi is used by the C format conversion programs (such as sga2bed, bed2sga, etc) to generate a hash table to link chromosome numbers to NCBI RefSeq identifiers and vice versa. When required, its location (<path>) must be set by using the -i|--db <path> option.

The text file chr_size is used by a few C program to fetch the chromosome size based on the corresponding chromosome NCBI identifier. In this way, it is possible to check whether the genome coordinates of the data files go beyond the chromosome boundaries.
