You need the additional jump because he forgot his jump :) His doesn't actually reset on 255. It prints 254 and then stops. Here is his program commented:

You need the additional jump because he forgot his jump :) His doesn't actually reset on 255. It prints 254 and then stops. Here is his program commented: RAM AD PC ADDR ________ _ _ ---- |----***-|-|*| ; read in SCRATCH (starts at 0) ---* |---*****|-|-| ; write it to OUTPUT --*- |--*-**-*|-|-| ; add ONE --** |---****-|-|-| ; write to SCRATCH -*-- |-*-*-**-|-|-| ; IF MAX, GOTO LBL_RESET -*-* |-*------|-|-| ; ELSE, start over -**- |----**--|-|-| ; LBL_RESET: read in ZERO -*** |---****-|-|-| ; write the ZERO to SCRATCH *--- |--------|-|-| ; fall off the world (I think this is where is missing jump is) *--* |--------|-|-| *-*- |--------|-|-| *-** |--------|-|-| **-- |--------|-|-| ; ZERO (r/o literal) **-* |-------*|-|-| ; ONE (r/o literal) ***- |--------|-|-| ; SCRATCH (r/w) **** | OUTPUT |-|-| If I change his "fall off the world" to a "start over" instruction (-*------) then it works fine