Re: What is your opinion about unsigned int u = -2 ?

On 8/9/24 2:19 PM, David Brown wrote:

On 09/08/2024 20:08, Bonita Montero wrote:

Am 08.08.2024 um 19:47 schrieb David Brown:
>

Think about negating a value.  For two's complement, that means inverting each bit and then adding 1.  For sign-magnitude, you
invert  the sign bit. For ones' complement, you invert each bit.

>
But with one's complement you have the same circuits for ading
and substracting like with unsigned values.

 If you are trying to say that for two's complement, "a + b" and "a - b" use the same circuits regardless of whether you are doing signed or unsigned arithmetic, then that is correct.  It is one of the reasons why two's complement became the dominant format.
 

No, a two's complement subtractor needs to invert the second operand, and inject a carry into the bottom bit. A one's complement subtractor just need to invert the second operand.
The fact that you want that carry input in the logic anyway for add-with-carry to make bigger additions, says that this doesn't really cost anything.