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tunik123
2 years ago

I don't know the term "representable" in this context; I suspect it means whether the difference can be represented as a signed number at all.

For the sake of clarity, I will assume 4-bit registers.

The number range is therefore between

1000 = -8 and 0111 = +7.

Example:

-6 = 1010, +6 = 0110

Subtracting (-6) – (+6) results in 0100, which is +4 and not -12. Therefore, the overflow flag is set.

So -12 cannot be represented.