How to make fonts bigger in **plain tex** math mode?

[Ulrike Fischer]

Am Fri, 28 Apr 2023 11:55:37 +0100 schrieb Philip Taylor (Hellenic
Institute):

>> Well your code doesn't work with pdftex (or xelatex) neither. 
> Why would you expect it to work with Xe/*La*/TeX ? 

Why don't you recognize a typo? It is so difficult to guess that I
meant xetex?

>> You introduced U+A0 (no break spaces) after some of the fontnames,
>> and now TeX is looking e.g. for cmr7U+A0 and is a bit unhappy.
> 
> I didn't /introduce/ them, they came from the PDF version of the TeXbook 
> from which I copied the relevant parts of Plain.TeX.
> works here under XeTeX, so I don't really know what your problem is or 
> where it originates — maybe your e-mail client ?

As your code errored for Steve too at the U+A0, I would say it is
more probable that the problem is on your side. 

-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/