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23278Re: [midatlanticretro] Re: Today is 11111

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  • Dan Roganti
    Nov 1, 2011

      On Nov 1, 2011 2:58 PM, <system@...> wrote:

      > 7(dec)+1(dec) is 8(dec)
      > 111(bin)+1(bin) is 1000(bin).
      > 8 or -8???

      Dude, did you get any sleep???
      When one specifies a size, in this case 5bit >>and<< signed integers (namely 2's comp), your number range is limited from
        -(2^(n-1)) to (2^(n-1))-1
      Unless of course, you intend to use doubles(or any multiple) - but then it still applies

      > 2's comp is a contrivance and has nothing to do with implementation in
      > hardware.

      jeesh, we know who failed Digital 101 now do we ;)
      Don't tell me, did you actually build an Full Adder >>and<< Subtractor Logic inside your ALU for class ??

      Two's Complement is the main reason you don't need extra hardware for Subtractor logic. You simply use Adder Logic only - even in Multipliers/Dividers. And so became the prevailing dominant method -- among several reasons -- over other signed integer notation, such as, Signed Magnitude, One's Comp, etc  -- beginning in the early 60's.
      Even DEC knew that ;)


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