2.3.17 Variable Pad Values

Variable pad values are used   in several situations.

1. When the first value is written to a new record, the other values in that record will contain the pad value. This also applies to hyper writes if less than the entire record is written. (The unwritten values will contain the pad value.)
2. When a new record is written that is more than one record beyond the last record already written, the intervening records will contain pad values. This will only happen if the record variance is VARY. (The variable values vary from record to record.)
3. When reading a record beyond the last record for a variable, pad values will be returned.
4. Allocated records for a variable which have not yet been written when a CDF is closed will be written using the variable's pad value.

The pad value for a variable may be specified   with the Internal Interface. It should be specified before any values are read from or written to the variable; otherwise the default pad value will be used. The pad value may be changed at any time (and any number of times) and will be in effect for all subsequent operations.

The default   pad value for each data type is as follows:

CDF_BYTE
0
CDF_INT1
0
CDF_UINT1
0
CDF_INT2
0
CDF_UINT2
0
CDF_INT4
0
CDF_UINT4
0
CDF_REAL4
0.0
CDF_FLOAT
0.0
CDF_REAL8
0.0
CDF_DOUBLE
0.0
CDF_EPOCH
01-Jan-0000 00:00:00.000 (0.0)
CDF_CHAR
" " (space character, 40 octal)
CDF_UCHAR
" " (space character, 40 octal)