BYTEBITS
# define BITMAPBYTES (BITMAPBITS / BYTEBITS) /* number of bytes in bit map */
# define _BITWORD(bit) (((unsigned char)(bit) / (BYTEBITS * sizeof (int))) & BITMAPMAX)
# define _BITBIT(bit) ((unsigned int)1 << ((unsigned char)(bit) % (BYTEBITS * sizeof (int))))