QBASIC PROGRAM TO FIND SUM OF DIGITS. SUB

DECLARE SUB SUM(N)
CLS
INPUT "ENTER ANY NUMBER";N
CALL SUM(N)
END

SUB SUM(N)
S=0
WHILE N<>0
R=N MOD 10
S=S+R
N=N\10
NEST I
PRINT "SUM OF DIGITS=";S
END SUB