The <ndbm.h> header defines the datum type as a structure that includes at least the following members:
void *dptr /* pointer to the application's data */ size_t dsize /* size of the object pointed to by dptr */
The size_t type is defined through typedef as described in <stddef.h>.
The <ndbm.h> header defines the DBM type through typedef.
The following constants are defined as possible values for the store_mode argument to dbm_store():
Insertion of new entries only.
Allow replacing existing entries.