2's complement representation of fractions?

Question

I\'m a little lost on this. I need to use two fractional bits 0.(a-1)(a-2)

Like that, now I can use .00 .01 .10 and .11 But I nee

Answer 1

see it this way:

you have normal binary representation

let's assume 8 bit words ...

the first bit (MSB) has the value 128, the second 64, and so on ...

in other words the first bit (MSB) is 2^7 ... the second bit is 2^6 ... and the last bit is 2^0

now we can assume our 8 bit word has 2 decimal places ....

we now start with the first bit (MSB) 2^5 and end with the last bit beeing 2^-2

no magic here ...

now to turn that into binary complement: simply negate the value of the first bit

so instead of 2^5 it would be -2^5

so base 10 -0.75 would be in binary complement
111111.01 ...
(1*(-32) + 1*16 + 1*8 + 1*4 + 1*2 +1*1 + 0*0.5 + 1*0.25)
(1*(-2^5) + 1*2^4 + 1*2^3 + 1*2^2 + 1*2^1 +1*2^0 + 0*2^(-1) + 1*2^(-2))