100 PROGRAM "Fibonacc.bas"
  110 FOR I=0 TO 10
  120   PRINT FIB(I);
  130 NEXT
  140 DEF FIB(K)
  150   SELECT CASE K
  160   CASE IS<0
  170     PRINT "Negative parameter to Fibonacci.":STOP
  180   CASE 0,1
  190     LET FIB=K
  200   CASE ELSE
  210     LET FIB=FIB(K-1)+FIB(K-2)
  220   END SELECT
  230 END DEF