Why is tab unaffected by font whereas space is affected?

[Otto Stolz]

Namasté (greeting in Sars-Cov-2 times ☺),

am 2020-04-17 um 15:42 Uhr hat Roger L. Costello geschrieben:
> I place a tab character before the string:
> 	a b
> I set the font of the tab character to Calibri. I note the position of the string.
> Then, I set the font of the tab character to Courier. The string is at the same position.

Where is the problem?

Imho, the Tab character signals that the next glyph shall be placed
at the next tabulator position in the current line, irrespective of
the current writing position (and irrespective of the current font).
This way, the Tab key has worked since the times of type-writers and
steam-computers ☺.

On the type-writer machine, you could chose the tabulator positions
mechanically; in contemporary text processing apps, you will have
some sort of paragraph format to set; simple plain-text editors,
such as Edlin under Windows, tend to assume their own, fixed tabulator
positions.

Best wishes,
    Otto Stolz