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## Re: [midatlanticretro] Re: Today is 11111

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• ... 7(dec)+1(dec) is 8(dec) 111(bin)+1(bin) is 1000(bin). 8 or -8??? 2 s comp is a contrivance and has nothing to do with implementation in hardware. So, what
Message 1 of 15 , Nov 1, 2011
Dan Roganti <ragooman@...> writes:

>On Nov 1, 2011 12:47 PM, <system@...> wrote:
>
>> I don't understand where your Flip-Flops comes into this nor have you
>> answered how 11111 = 111111. >
>
>Because it's a joke, remember, its when your supposed to laugh ;)
>
>Twos Complement is not bound to any field, or number coding on whatever
>system. It's how you implement it in hardware.
>
>The only rule (in shorthand) to get 2's Comp is simply 1. Invert Binary
>Number 2. Add 1

7(dec)+1(dec) is 8(dec)

111(bin)+1(bin) is 1000(bin).

8 or -8???

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

So, what you're saying is that if I add enough to 'n' it will eventually
become negative? I don't remember the number line folding back.
• ... Dude, did you get any sleep??? When one specifies a size, in this case 5bit and
Message 2 of 15 , 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 ;)

=Dan

• ... Hey. HEY. Watch it there, mister! ;) -- Dave McGuire New Kensington, PA
Message 3 of 15 , Nov 1, 2011
On 11/01/2011 04:10 PM, Dan Roganti wrote:
> 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 ;)

Hey. HEY. Watch it there, mister! ;)

--
Dave McGuire
New Kensington, PA
• ... Were did one specify the size? We re back at my first post. ... No shite sherlock but I don t have to treat that addition as producing a negative. I m
Message 4 of 15 , Nov 1, 2011
Dan Roganti <ragooman@...> writes:

>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

Were did one specify the size? We're back at my first post.

>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,

No shite sherlock but I don't have to treat that addition as producing
a negative. I'm perfectly happy, with my example, to continue counting
to 15 (1111) and then start it all over again. Of course, I'd generate
an OVERFLOW exception or set some overflow flag/status bit but I don't
necessarily have to. And, yes, I do understand digital logic... 1000
is not negative unless I intend to treat it as negative. Hence, it's a
contrivance.

>Signed Magnitude, One's Comp, etc -- beginning in the early 60's. Even
>DEC knew that ;)

where and why did they have to do with this?
• ... Dude, Today is 11111 ;)
Message 5 of 15 , Nov 1, 2011

On Nov 1, 2011 4:33 PM, <system@...> wrote:
>
>
> No shite sherlock
>

Dude,
Today is 11111 ;)

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