**1-based coordinate system A coordinate system where the first base of a sequence is one. In this coordinate system, a region is specified by a closed interval. For example, the region between the 3rd and the 7th bases inclusive is [3, 7]. The SAM, VCF, GFF and Wiggle formats are using the 1-based coordinate system.
**0-based coordinate system A coordinate system where the first base of a sequence is zero. In this coordinate system, a region is specified by a half-closed-half-open interval. For example, the region between the 3rd and the 7th bases inclusive is [2, 7). The BAM, BCFv2, BED, and PSL formats are using the 0-based coordinate system.