Re: A86: cphlde
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Re: A86: cphlde
Thanks. That's useful information. I wasn't sure what you meant by
signed and unsigned, or even aware that numbers in assembly could be
unsigned.
>
> Yes, it DOES matter what kind of numbers you're using. For example, $FF
> is either -1 or 255, depending on whether or not you're using signed
> math. Here are some 8-bit examples (I hope I did the math right):
>
> hexadecimal signed decimal unsigned decimal
> FE -2 254
> -07 - 7 - 7
> --- --- ----
> F7 -9 247
> In this case, the sign bit is set and the carry flag is clear.
>
> hexadecimal signed decimal unsigned decimal
> 07 7 7
> -FE --2 -254
> --- --- ----
> 09 9 9
> In this case, the sign bit is clear and the carry flag is set.
>
> If your application uses signed numbers, you use the sign bit to determine
> which operand is larger. If your application uses unsigned numbers, you
> use the carry flag to determine which operand is larger.
>
> --------
> Dan Eble (mailto:eble@cis.ohio-state.edu)
> (http://www.cis.ohio-state.edu/~eble)
>
> "Behold, how great a matter a little fire kindleth!" -- James 3:5
References: