Although neither the draft C99 standard nor the draft C11 standard support binary literals, since you specifically mention gcc
it has an extension for binary literals which says:
Integer constants can be written as binary constants, consisting of a sequence of ‘0’ and ‘1’ digits, prefixed by ‘0b’ or ‘0B’. This is particularly useful in environments that operate a lot on the bit level (like microcontrollers).
they gives the following example (see it live):
i = 0b101010;
and it looks like clang
also support this as an extension as well (see it live):
[...]binary literals (for instance, 0b10010) are recognized. Clang supports this feature as an extension in all language modes.
This is not available in standard C++ either until C++14 [lex.icon].