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