Program to print only vowels from given word using SUB

DECLARE SUB DISPLAY(N)
CLS
INPUT"ENTER ANY WORD";N$
CALL DISPLAY(N$)
END

SUB DISPLAY(N$)
FOR I= 1 TO LEN(N$)
B$= MID$(N$,I,1)
C$= UCASE$(B$)
IF C$="A" OR C$="E" OR C$="I" OR C$="O" OR C$="U" THEN D$=D$+B$
NEXT I
PRINT"VOWELS="D$
END SUB