Oracle Forms-DEFAULT_VALUE Built-in

DEFAULT_VALUE built-in in oracle forms is used for assign value to variable if value of variable is NULL.
IF :DBT_BRANCH.LOCATION IS NULL THEN
:DBT_BRANCH.LOCATION:='Pune';
END IF;
is equivalent to
default_value('Pune','DBT_BRANCH.LOCATION');
But DEFAULT_VALUE is noramally used to initialize global variable if they are not exist. If global variable are not exist in system then it will create new one or else assign value if its value is NULL.