Trying to understand one's complement

Question

I was going through some problems so that I could understand one's complement and had a question about one similar to this.

If this binary number is in one's complement format already: 1010 1111 1111

What decimal number does it represent?

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Am I correct in this process? 1010 1111 1111 has a negative sign (far left bit).

Then take the complement: 0101 0000 0000 = 1280

So it represents -1280? Or is this completely wrong.

Answer 1

That is correct IF you have a 12-bit storage. If your storage was 16-bits, for example, the number would not be negative (because the missing bits are assumed to be zero).