DBMS_SQL.define_column ---- why ????

[Jason Tomlins]

As an SQL newbie, why do I need to define columns prior to getting
column_value when I can fetch_rows(cur_ hdl) ?? Does not column_value
get the value at position x at the current cursor position and
fetch_rows gets a row for a given cursor and increment cursor position
? So why define_column ?

Example.

-- describe defines
dbms_sql.define _column(cur_hdl , 1, name, 200);
dbms_sql.define _column(cur_hdl , 2, salary);

-- execute
rows_processed := dbms_sql.execut e(cur_hdl);

LOOP
-- fetch a row
IF dbms_sql.fetch_ rows(cur_hdl) 0 then

-- fetch columns from the row
dbms_sql.column _value(cur_hdl, 1, name);
dbms_sql.column _value(cur_hdl, 2, salary);

-- <process data>

ELSE
EXIT;
END IF;
END LOOP;


Thanks for any input.
Jason Tomlins