The first leftmost bit i.e. the most significant bit in the sign magnitude represents if the number is positive or negative. If the MSB is 1, the number is negative else if it is 0, the number is positive. Here, +1=0001 and for -1=1001.
The IEEE is an organization of professionals in the field of electronics and electrical engineering. IEEE has given certain standards of its own which are followed in the field of computer science and electrical engineering.