>> (1) what does - 32769 look like ?
>=20
> Exactly like +32767

Therefore in 16 bits you couldn't differentiate the two. So then
there must be more, to maintain the sign

Having a play with Calculator

32767 =3D 0x7FFF, 32769 =3D 0x8001

16777216 (0x1000000) - 32769 =3D 16744447 (0xFF7FFF)
16777216 - 32770 =3D 0xFF7FFE
16777216 - 32767 =3D 0xFF8001

and

4294967296 (0x100000000) - 32769 =3D 4294934527 (0xFFFF7FFF)

If that's right then the maths will have to be 24-bit, with the sign
still in bit 15, but negated logic

Joe
--=20
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