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if (message.message & 0x0004)

Is message.message & 0x0004 a statement?? And what does it mean??

thanks,
Allan, newbie in c-programming

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holst skrev:

>if (message.message & 0x0004)

message.message is a variable (message) in a struct (message).
The programmer is not good at finding descriptive variable names.

& is a bitwise operator, AND.

0x means that the number is written i hexcode, but it might as
well have been written as 4.

   Decimal;   Binary:
    137      10001001
    4      00000100
   ------------------------------
137 & 4: 0      00000000

   Decimal:   Binary:
    173      10101101
    4      00000100
   ------------------------------
137 & 4: 4      00000100

>Is message.message & 0x0004 a statement?

Yes, for proper values of "statement".

>And what does it mean?

That all other bits than the 2nd one (count from right and start
with number 0) are turned off.

God fornøjelse ... nå nej, jeg glemte jo at du er engelsk (ved
Auc?)

--
Bertel
http://lundhansen.dk/bertel/   FIDUSO: http://fiduso.dk/

---

Thank for your helping, but the last thing you wrote I don't quite
understand


"Bertel Lund Hansen" <nospamto@lundhansen.dk> wrote in message
news:l4qffts3pjvp75rlie21tft6m8b40b89h0@sunsite.auc.dk...
> holst skrev:
>
> >if (message.message & 0x0004)
>
> message.message is a variable (message) in a struct (message).
> The programmer is not good at finding descriptive variable names.
>
> & is a bitwise operator, AND.
>
> 0x means that the number is written i hexcode, but it might as
> well have been written as 4.
>
> Decimal; Binary:
> 137 10001001
> 4 00000100
> ------------------------------
> 137 & 4: 0 00000000
>
> Decimal: Binary:
> 173 10101101
> 4 00000100
> ------------------------------
> 137 & 4: 4 00000100
>
> >Is message.message & 0x0004 a statement?
>
> Yes, for proper values of "statement".
>
> >And what does it mean?
>
> That all other bits than the 2nd one (count from right and start
> with number 0) are turned off.
>
> God fornøjelse ... nå nej, jeg glemte jo at du er engelsk (ved
> Auc?)
>
> --
> Bertel
> http://lundhansen.dk/bertel/ FIDUSO: http://fiduso.dk/

---

>
> >Is message.message & 0x0004 a statement?
>
> Yes, for proper values of "statement".
>
> >And what does it mean?
>
> That all other bits than the 2nd one (count from right and start
> with number 0) are turned off.

This is not entirely correct, no bits are flipped here.

(message.message & 0x0004) is a boolean statement that is true if the 3rd
bit is set in message.message and false otherwise.

Claus

---

Claus Brinch Jensen skrev:

>This is not entirely correct, no bits are flipped here.

Du har ret.

--
Bertel
http://lundhansen.dk/bertel/   FIDUSO: http://fiduso.dk/