Can I use base-2 constants
(something like 0b101010)?
Is there a printf format for binary?
A: No, on both counts, although there are various preprocessor tricks you can try (see the links below). You can convert base-2 string representations to integers with strtol. If you need to print numbers out in base 2, see the example code in question 20.10.
example by Jack Klein
preprocessor trick by Karl Heuer
prettier preprocessor trick by Bill Finke