Yes, that is basically how C works, though the C standard describes it in a weird way. There is the notion of a “preprocessor number” which starts with a digit

Yes, that is basically how C works, though the C standard describes it in a weird way. There is the notion of a “preprocessor number” which starts with a digit and allows any characters that can appear in a number or identifier. At a later step in parsing it is converted to a strict number, which would fail in a case like 0xfor.