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From: Thiago Adams <thiago.adams@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: how cast works?
Date: Thu, 8 Aug 2024 08:14:25 -0300
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On 07/08/2024 17:00, Dan Purgert wrote:
> On 2024-08-07, Thiago Adams wrote:
>> How cast works?
>> Does it changes the memory?
>> For instance, from "unsigned int" to "signed char".
>> Is it just like discarding bytes or something else?
>> [...]
> 
> I don't know what happens when you're changing datatype lengths, but if
> they're the same length, it's just telling the compiler what the
> variable should be treated as (e.g. [8-bit] int to char)
> 
>>
>> I also would like to understand better signed and unsigned.
>> There is no such think as "signed" or "unsigned" register, right?
> 
> "Signed" just means the first bit indicates negative.
> 
> So an "unsigned" 8 bit integer will have the 256 values ranging from
> 
>   0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
>        (0b00000000)
> 
>                TO
> 
>   128 + 64 + 32 + 16 + 8 +4 + 2 + 1 = 255
>        (0b11111111)
> 
> 
> Whereas a "signed" 8 bit integer will have the 256 values ranging from
> 
>    (-128) + 0 + 0 + 0 + 0 + 0 + 0 + 0 = -128
>        (0b10000000)
> 
>                TO
> 
>    0 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 127
>        (0b01111111)
> 
> At least in two's compliment (but that's the way it's done in C)
> 
> 
>> How about floating point?
> 
> Floating point is a huge mess, and has a few variations for encoding;
> though I think most C implementations use the one from the IEEE on 1985
> (uh, IEEE754, I think?)
> 



I didn't specify properly , but my question was more about floating 
point registers. I think in this case they have specialized registers.