fib.bf

Move right and request number
>
Get char
,---- ---- --
[
  ++++++++++
  >[-]>[-]>[-]<<< Reset next two slots
  > ++ ++++ ++++ <
  <[->>>+<<<] Copy number to next two slots
  >>
  [
    - Decrement for mult
    >[-<<<+>>>>+<]
    >[-<+>]
    <<
  ]<
  
  Parse number (subtract '0')
  >[-]
  >[-]++++ ++++ ++++ ++++
  [-<+++[-<->]>]
  <<
  [-<+>]
  
  ,---- ---- --
]<

> move to A and keep 0
>+ move to B and set to 1
<< move back to N
[
  move to B
  >>
  copy B to C and D
  [->+>+<<]
  Move to A
  <
  Add A to C (now C is A plus B)
  [->>+<<]
  Move to D
  >>>
  Add D to A (A = B)
  [-<<<+>>>]
  <[-<+>]
  <<<
  -
]
>.