S9 LIB  (binary-string->integer string)             ==>  integer
        (integer->binary-string integer1 integer2)  ==>  string
        (number-of-bits integer)                    ==>  integer

INTEGER->BINARY-STRING writes a binary notation of INTEGER
to a fresh string and returns it. The resulting string will
be INTEGER2 characters wide and will consist of zeros and
ones exclusively. INTEGER2 must be large enough to hold the
desired binary representation. NUMBER-OF-BITS may be used
to find this value.

BINARY-STRING->INTEGER converts the binary representation of
an integer contained in STRING to an integer. It basically
does the same as STRING->NUMBER with a radix of 2, but is
hopefully more efficient.

NUMBER-OF-BITS returns the least number of bits that is
needed to store the given integer in binary format.

(integer->binary-string 123 8)       ==>  "01111011"
(binary-string->integer "01111011")  ==>  123
(number-of-bits 127)                 ==>  7
