why do we have terminology of positive and negative zero ?

Question

If we use diminished radix representation then representation for 0 will be b^n-1 where b is the base so this representation is for 0 , how come we are associating +0 and -0 for this ?

Normally also we have representation for 0 , so again this b^n-1 is a representation for 0 so why to associate sign to it ?

Comments

as far i know in signed 1's complement 0 has two representation $0^+$ = 000 and $0^-$ = 111 

but in 2's complement we have only one representation of 0 i.e why we use 2's complement in negative number coz in ones complement we have two representation for 0

Answer 1

lets take example for all the cases. signed , unsigned , 1;s and 2's . i think they generated the system by dividing all the numbers into half,. But they even willingly can't represent +0 and -0 see this 

	10	-10	+0	-0
unsigned	1010	n/a	0000	n/a
signed	01010	11010	00000	10000
1's	01010	10101	00000	11111
2's	01010	10110	00000	00000

everything other than zero has different form except zero . so even though they thought of following the same convention it could not be followed.