(Corresponds to Section 4.3 of ANSI X3.9-1978 FORTRAN 77.)
An integer constant also may have one of the following forms:
B'binary-digits'
O'octal-digits'
Z'hexadecimal-digits'
X'hexadecimal-digits'
binary-digits, octal-digits, and hexadecimal-digits
are nonempty strings of characters in the set 01, 01234567,
and 0123456789ABCDEFabcdef, respectively.
(The value for A (and a) is 10, for B and b
is 11, and so on.)