description: Returns a pointer to the data in a specified column and row of the current data table of a
data set. Only the rows that are “of interest” are returned.
SDDS_table: Address of the SDDS_TABLE structure for the data set.
column_name: A NULL-terminated string giving the name of the column for which
data is desired.
srow_index: Index of the row desired in the list of selected rows (or “rows of interest”).
memory: Address of location into which to write the data. If NULL, memory is allocated
for this purpose.
return value: On success, returns the address into which the data was placed. This pointer should be cast to
data-type*, where data-type is the data type of the columns selected. Note that for type
SDDS_STRING, data-type is char *.
On failure, returns NULL and records an error message.