Numeric Types A shapefile stores integer and double precision numbers. The remainder of this document wilt refer to the following types: Integer Signed 32-bit integer (4 bytes) D Double: Signed 64-bit IEEE double-prec inion Noating point number (8 bytes) Floating point numbers must be numeric values. Positive infinity, negative infinity, and Not-a-Number (NaN) values are not allowed in shapefiles Nevertheless, shapefiles support the concept of "no data" values, but they are currently used only for measures. Any floating point number smaller than 10 is considered by a shapefile reader to represent a "no data" value. The first section below describes the general sineture and arganization ofthe shapefils The second section describes the record contents for each type of shape supponed in the shapefile. ation of the The main file (shp) contains a fixed-length fibe header followed by variable-length Main File 'records. Each variable-length record is made up of a fixed-length record header followed by variable-length record contents. Figure illustrates the main file organization.