QBASIC to Reverse of Input string using SUB

DECLARE FUNCTION REV $ ( N$ )
CLS
INPUT "Enter name"; N$
PRINT "Reverse string is"; REV$ ( N$ )
END

FUNCTION REV$ ( N$ )
FOR I = LEN ( N$ ) TO 1 STEP -1
B$ = MID $ ( N$, I, 1)
C$ =  C$ + B$
NEXT I
REV$ = C$
END FUNCTION