Fig. 1

Structure of Genotype Block (GTB) and byte-encoded table of genotype (BEG) implemented in GBC. a Magic code: the first two bytes are used to store the compressed parameters. Block numbers: the total number of blocks contained in the compressed file, which also indicates that the “block abstract information” at the end of the file has (25*numbers) bytes of memory. Meta information: the meta information in the header of the VCF file. Subjects information: list of subjects. Block entity data: the compressed data is combined according to the order of the abstract block information. Abstract block information: abstract information of the GTB nodes for building the first-level fast index table. b The byte-encoding table of genotype (BEG)