For example, speaking AbcDEg
, over a phone.
"capital A,b,c, capital D, capital E, g"
or
"uppercase A,b,c, uppercase D, uppercase E, g"
or some way else?
To keep ambiguity at a minimum, I would recite this as:
Capital A, lowercase b, lowercase c, capital D, capital E, lowercase g.
Otherwise, the phrase "Capital a, b, c" could be interpreted as ABC
, as the modifier capital could apply to more than one letter that follows.
As for whether to use uppercase or capital, both are readily understood, although the Ngram shows that, at least in written texts, capital seems to be the predominant form.
It's usually capital instead of uppercase.
This is how it was done in the 1920s in a London advertising agency dictating copy to a newspaper:
“Now, third line, Goudy 24-point upper and lower. Start under the W. 'Waste Nerve-Power!' Capital N, capital P, and screamer. Got that?”
“Yes; I'll repeat. First line Goudy caps., starting level with cap A of present headline. O,V,E,R, hyphen, W,O,R,K, ampersand; second line, same fount, 2 ems to the right, O,V,E,R, hyphen, W,O,R,R,Y, dash. Third line. Start under W, Goudy 24 point upper and lower: lower-case w,a,s,t,e, capital N,e,r,v,e, hyphen, capital P,o,w,e,r, screamer. That O.K.?”
“That's right. Much obliged.”
Murder Must Advertise. A Detective Story.
Author: Sayers, Dorothy Leigh (1893-1957)
https://gutenberg.ca/ebooks/sayers-advertise/sayers-advertise-00-h.html
Page 125 - 126
This of course was in the days when upper- and lower-case actually referred to the typecases of type used for making up the formes. (Mechanical typesetting would have been used for body text, but advertisements and display work would still have been hand set at this time.)
Sayers's longest employment was from 1922 to 1931 as a copywriter at S.H. Benson's advertising agency, located at International Buildings, Kingsway, London. ...
Sayers was quite successful as an advertiser. Her collaboration with artist John Gilroy resulted in "The Mustard Club" for Colman's Mustard and the Guinness "Zoo" advertisements, variations of which still appear today.
https://en.wikipedia.org/wiki/Dorothy_L._Sayers#Poetry,_teaching,_and_advertisements