Check input character is capital or small using function

DECLARE FUNCTION CHECK$(A$)
CLS
INPUT "ENTER ANY CHARACTER"; A$
PRINT "THE ENTERED CHARACTER IS "; CHECK$(A$)
END

FUNCTION CHECK$ (A$)
C = ASC(A$)
IF C >= 65 AND C <= 91 THEN
CHECK$ = "UPPERCASE"
ELSEIF C >= 97 AND C <= 122 TCHECK
CHECK$ = "LOWERCASE"
END IF
END FUNCTION