Originally Posted by C89 Draft
3.1.2.5 Types: The type char, the signed and unsigned integer types, and the enumerated types are collectively called integral types. The representations of integral types shall define values by use of a pure binary numeration system.13 American National Dictionary for Information Processing Systems.) The representations of floating types are unspecified.
Footnote 13: A positional representation for integers that uses the binary digits 0 and 1, in which the values represented by successive bits are additive, begin with 1, and are multiplied by successive integral powers of 2, except perhaps the bit with the highest position.