Writing bits to a file in C

Question

I have this string: \"101\" I want to write it to a file, in C, not as text: \"101\" and so 8 bits x char. but directly use the string as bits: the bit \"1\", the bit \"0\" and

Answer 1

What you can do is write it as bits (3) and fill it up to a byte with 0's. However, you also need to start (or end) with the number of bits (or bits from the last byte) that are really used.

E.g. (using first byte as length):

00000011   -> 3, meaning from the last (and only byte in this case, 
              only the first 3 bits are used)
10100000   -> 101 is the string, other 5 bits are 0, just use for padding

In this case the overhead of the first (length) byte is 50%, the longer the string, the less the overhead percentage of course.