bit representation of ieee 754 floating point numbers

a.c

#include <stdio.h>
int
main(int argc, char **argv)
{
        float f;
        unsigned int i, mask;

        f = 1.5;
        i = *(unsigned int *)(void *)&f;
        for (mask = 1 << 31; mask > 0; mask >>= 1) {
                putchar((i & mask) ? '1' : '0');
                if (mask == 1 << 31 || mask == 1 << 23)
                        putchar(' ');
        }
        puts("");

        i = 0xffffffff;
        f = *(float *)(void *)&i;
        printf("0x%x = %g\n", i, f);
}

0 01111111 10000000000000000000000
0xffffffff = nan