The constants include integers such as:-

                                0 1   999   -512

In UNSW Prolog, integers are restricted to the range -2^31 to 2^31-1 on the
VAX and -2^15 to 2^15-1 on the PDP-11.

Constants include reals such as:-

		    0.0   1.0   34.45  -23.45  3.45e-02

In  prolog,  reals  have the same range as float in C.  Printing reals will
only give 4 decimal place accuracy.

Constants also include atoms such as:-

                        a void   =   := 'Algol-68'   []

The  symbol  for an atom can be any sequence of characters, which should be
written  in  quotes if there is possibility of confusion with other symbols
(such  as  variables, integers).  As in conventional programming languages,
constants  are  definite elementary objects, and correspond to proper nouns
in natural language.