This doesn't really belong here but:

A special way to generate integers is by getting the unicode code point:

?- X = 0'A.
X = 65.

?- X = 0'\s.
X = 32.

In the ISO standard, this is described "§6.4.4 - Integer numbers" (although the character-to-integer mapping is left unspecified) as:

character code constant = "0", single quote char, single quoted character