Even F4 does not like lower case text.
20 FORMAT('A test line')
This is the general case for most (if not all) PDP8 languages.
Typically, ASCII is stored in packed 6bit codes (2 per 12 bit word)
as a result, the character set is limited....
However, OS/8 itself stores ascii in packed 8 bit characters (3 per 2*12 bit words)
So, you can edit files containing lower case chars but don't expect compilers to do much with them.
NB: the Basic editor doesn't even let you enter LC chars!!!