

Using a Terminal without Lower-Case

KEY
The  standard  syntax  of  Prolog  assumes  that  a full ASCII character set is
available.  With this "full character set" or 'LC'  convention,  variables  are
(normally)  distinguished  by  an initial capital letter, while atoms and other
functors must start  with  a  lower-case  letter  (unless  enclosed  in  single
quotes).

When  lower-case is not available, the "no lower-case" or 'NOLC' convention has
to be adopted.  With this convention, variables must  be  distinguished  by  an
initial  underline  character  "_",  and the names of atoms and other functors,
which now have to be written in  upper-case,  are  implicitly  translated  into
lower-case (unless enclosed in single quotes). For example:

            _VALUE2

is a variable, while

            VALUE2

is 'NOLC' convention notation for the atom which is identical to:

            value2

written in the 'LC' convention.

The  default  convention  is 'LC'. To switch to the "no lower-case" convention,
call the built-in procedure 'NOLC', e.g.  by the directive:

            | ?- 'NOLC'.

To switch back to the  "full  character  set"  convention,  call  the  built-in
procedure 'LC', e.g.  by:
            | ?- 'LC'.
Note  that  the names of these two procedures consist of upper-case letters (so
that they can be referred to on all devices),  and  therefore  the  names  must
ALWAYS be enclosed in single quotes.

It is recommended that the 'NOLC' convention only be used in emergencies, since
the standard syntax is far easier to use and is also easier for other people to
read.