c - Getting negative value with bit-fields -

i have question related bit-fields in c. here have such structure:

struct register {   int bit:1; };  int main(void) {   struct register bit = {1};    printf("\nbit = %d", bit.bit);   return 0; } 

can please explain me why get:

bit = -1

if you're working bitfields, should use unsigned int. signed int problem bit-fields.