Documented in Volume 1 of the UNIX Programmers Manual.
% ed -u filename
will cause ed to convert all alphabetics into upper-case. This can
be useful for searching for strings in a case-independent fashion.
See grep -i for a better way....
WARNING: 'ed' is not the preferred line editor because of its terseness
and awkward user interface. Unless you specifically prefer it for some
reason, a better choice is 'ex'.
See /usr/doc/edtut and adv.ed on 4.2 BSD systems for additional online documentation on ed.