Atomic Data Types
| CDL | netCDF-C | netCDF-Java | Description | Availability |
|---|---|---|---|---|
| char | NC_CHAR | CHAR | 8-bit character | Classic, Enhanced, CDF‑5 |
| byte | NC_BYTE | BYTE | 8-bit signed integer | Classic, Enhanced, CDF‑5 |
| short | NC_SHORT | SHORT | 16-bit signed integer | Classic, Enhanced, CDF‑5 |
| int | NC_INT | INT | 32-bit signed integer | Classic, Enhanced, CDF‑5 |
| long | NC_LONG | — | Deprecated: synonymous with int | — |
| float | NC_FLOAT | FLOAT | IEEE single-precision floating point (32 bits) | Classic, Enhanced, CDF‑5 |
| real | — | — | Deprecated: Synonymous with float | — |
| double | NC_DOUBLE | DOUBLE | IEEE double-precision floating point (64 bits) | Classic, Enhanced, CDF‑5 |
| ubyte | NC_UBYTE | UBYTE | Unsigned 8-bit integer | Enhanced, CDF‑5 |
| ushort | NC_USHORT | USHORT | Unsigned 16-bit integer | Enhanced, CDF‑5 |
| uint | NC_UINT | UINT | Unsigned 32-bit integer | Enhanced, CDF‑5 |
| int64 | NC_INT64 | LONG | 64-bit signed integer | Enhanced, CDF‑5 |
| uint64 | NC_UINT64 | ULONG | Unsigned 64-bit signed integer | Enhanced, CDF‑5 |
| string | NC_STRING | STRING | Variable-length string of characters | Enhanced |
The netCDF atomic data types were chosen to provide a reasonably wide range of trade-offs between data precision and number of bits required for each value. They are independent from whatever internal data types are supported by a particular machine and language combination.
The netCDF atomic data types provide a variety of integer, floating point, and character data types. The data types in different programming languages and on different computing platforms will not necessarily align with the netCDF atomic data types. In those cases conversions will be necessary and are generally handled by the different language libraries. (More details on conversions in ???section???.)
Converting from one numeric type to another may result in an error if the target type is not capable of representing the converted value.
Note that mere loss of precision in type conversion does not return an error. Thus, if you read double precision values into a single-precision floating-point variable, for example, no error results unless the magnitude of the double precision value exceeds the representable range of single-precision floating point numbers on your platform. Similarly, if you read a large integer into a float incapable of representing all the bits of the integer in its mantissa, this loss of precision will not result in an error. If you want to avoid such precision loss, check the external types of the variables you access to make sure you use an internal type that has adequate precision.
It is possible to interpret byte data as either signed (-128 to 127) or unsigned (0 to 255). However, when reading byte data to be converted into other numeric types, it is interpreted as signed.
Byte data in netCDF
String data types in netCDF
Char array Strings
String data type in Enhanced Data Model
String character encodings (UTF-8)
User Defined Data Types
The Enhanced Data Model supports compound types (similar to C-structs), VLEN types (which can be used for ragged arrays), opaque types ( to blobs of )