TeX provides the two primitives
changing the case of text. Unfortunately, these TeX primitives do
not change the case of characters accessed by commands like
\aa. To overcome this problem, LaTeX provides these two commands.
In the long run, we would like to use all-caps fonts rather than any
\MakeUppercase but this is not possible at the moment
because such fonts do not exist.
For further details, see clsguide.tex.
In order that upper/lower-casing will work reasonably well, and in
order to provide any correct hyphenation, LaTeX2e must use,
throughout a document, the same fixed table for changing case.
The table used is designed for the font encoding
T1; this works well
with the standard TeX fonts for all Latin alphabets but will cause
problems when using other alphabets.