Geographic Information System (GIS) - File Formats / Shapefiles (Continued)
Mandatory Files -
.shp — shape format; the feature geometry itself
.shx — shape index format; a positional index of the feature geometry to allow seeking forwards and backwards quickly
.dbf — attribute format; columnar attributes for each shape, in dBase IV format
Other Files -
prj — projection format; the coordinate system and projection information, a plain text file describing the projection using well-known text format
.sbn and .sbx — a spatial index of the features
.fbn and .fbx — a spatial index of the features that are read-only
.ain and .aih — an attribute index of the active fields in a table
.ixs — a geocoding index for read-write datasets
.mxs — a geocoding index for read-write datasets (ODB format)
.atx — an attribute index for the .dbf file in the form of shapefile.columnname.atx (ArcGIS 8 and later)
.shp.xml — geospatial metadata in XML format, such as ISO 19115 or other XML schema
.cpg — used to specify the code page (only for .dbf) for identifying the character encoding to be used
.qix — an alternative quadtree spatial index used by MapServer and GDAL/OGR software
In each of the .shp, .shx, and .dbf files, the shapes in each file correspond to each other in sequence (i.e., the first record in the .shp file corresponds to the first record in the .shx and .dbf files, etc.). The .shp and .shx files have various fields with different endianness, so an implementer of the file formats must be very careful to respect the endianness of each field and treat it properly.