Check width

gistfile1.c

#include <stdio.h>
#include <stdbool.h>

int main (void)
{
        /* PARAMETERS */

        /* Upper bound of loop (inclusive) */
        const unsigned int upper_bound = 12;

        /* width is the minimal length of the outputted binary number
         * (no truncation, it can be bigger). */
        const unsigned int width = 56;

        /* Padding character. */
        const char padchar = '-';

        /* ITERATING AND PRINTING */

        const int bitcount = (8 * sizeof(unsigned int));
        const int extraneous = width - bitcount;
        
        /* Bits below width_threshold should be left-padded. */
        const unsigned int width_threshold =
                (extraneous < 0) ? (1 << width) : -1;
        
        /*     111...111 
             ^ 011...111
             -----------
               100...000  */
        const unsigned int largest = -1;
        const unsigned int bitmask_max = largest ^ (largest >> 1) ;

        unsigned int i = 0;
        for(i = 0; i <= upper_bound; ++i) {
                unsigned int mask;

                /* Did we encounter only zeros so far? */
                bool only_zeroes = true;

                /* Pad the extraneous bits */
                int j;
                for(j = 0; j < extraneous; ++j) {
                        putchar(padchar);
                }
                
                /* Loop over bits from the most-significand ones to the least */
                for(mask = bitmask_max; mask > 0; mask >>= 1) {
                        const bool bit = (i & mask);
                        only_zeroes &= !bit;
                        if (only_zeroes && mask >= width_threshold) {
                                /* Only zeroes so far, no padding yet */
                                continue;
                        }
                        putchar(bit
                                ? '1'
                                /* "mask > 1" ensures i == 0 is
                                 * printed as '0', not as padchar */
                                : ((only_zeroes && mask > 1)
                                   ? padchar
                                   : '0'));
                }
                putchar('\n');
        }
}