DECLARE EXTERNAL FUNCTION ☆
DECLARE EXTERNAL FUNCTION identifier, identifier, ･･･, identifier
designates that the identifiers succeeding DECLARE EXTERNAL FUNCTION are the names of external functions in the program unit where this statement exists.
BASIC gives the priority to the supplied functions in the program unit that lacks the designation by this statement.
Example.

    10 DECLARE EXTERNAL FUNCTION INT
    20 PRINT INT(3)
    30 END
    100 EXTERNAL FUNCTION INT(n)
    110 LET INT=n^3-1
    120 END FUNCTION

If the 10-line lacks in the above program, INT in the 20-line means the supplied function INT.