SWI-Prolog implements both Edinburgh and ISO representations for
non-decimal numbers. According to Edinburgh syntax, such numbers are
written as <radix>'<number>,
where <radix> is a number between 2 and 36. ISO defines
binary, octal and hexadecimal numbers using
0[bxo]<number>. For example: A is 0b100 \/ 0xf00
is a valid expression. Such numbers are always unsigned.