100 PROGRAM "Fibonac.bas"
110 FOR I=0 TO 20
120   PRINT "F";I,FIB(I)
130 NEXT
140 DEF FIB(N)
150   NUMERIC I
160   LET A=0:LET B=1
170   FOR I=1 TO N
180     LET T=A+B:LET A=B:LET B=T
190   NEXT
200   LET FIB=A
210 END DEF