>>> Like all digitally encoded information, it has unavoidably the uncomfortable property that the smallest possible perturbations —i.e. changes of a single bit— can have the most drastic consequences.

>> Error correcting codes do exist!

He acknowledged this explicitly immediately after, on the next sentence:

> [For the sake of completness I add that the picture is not essentially changed by the introduction of redundancy or error correction.]

Think of what happens if a single bit is changed in the error-correcting part of the program.