That was a good guess. The NEC documentation actually makes the same
mistake. As you noticed, the snippet I posted calls CHR$(127),  "Back
Space", which is incorrect, but in a later chapter the error gets
compounded:

7. Bad data in DO file
> You cannot store data which include a character whose code is 0, ^X8 or
> ^X1A. The '0' is a 'NULL' to indicate a hole which is not used. Or double
> NULL means the end of the BA file. The ^X8 is 'Back Space'. The ^X1A is
> regarded as the end of the DO file, as you know. Refer to 'DO file'.
>

It seems someone read the word "Back Space" and had the reasonable
conclusion that CHR$(8) was meant. I haven't tested on a NEC PC-8201A, but
at least on my Tandy 200, it is CHR$(127) that is invalid in a DO file.

By the way, I'm rather enjoying reading this documentation which has
surprising moments of charm. Although a technical reference, the authors
occasionally let out a wonderful, youthful enthusiasm for the PC-8201A,
full of so much hope for what people will do in the future with this
incredible machine. From the introduction:

With this manual, may you make super programs for your own purpose !!
>
Mr. Hiroaki Yokoyama, Software Engineer
> Personal Computer Development Division
>

Indeed, Mr. Yokoyama. Even nearly forty years in your future, with your
manual we are making super programs.

—b9

On Thu, Aug 18, 2022 at 11:14 AM Joshua O'Keefe <[email protected]>
wrote:

> > On Aug 18, 2022, at 11:12 AM, Joshua O'Keefe <[email protected]>
> wrote:
> > conjecture, but aren't ^@, ^H, and ^Z control characters that affect
> console output
>
> Apologies for replying to myself; I realize on reflection CHR$(127) is ^?
> (DEL) rather than ^H (BS) isn't it?

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