RE: [Dev-C++] Question about pointers (beginner)

[Smurf, P. <smu...@xs...>]

You are correct I misread it.

Thanks

> -----Original Message-----
> From: dev...@li...
> [mailto:dev...@li...]On Behalf Of OROSZI
> Bal=E1zs
> Sent: dinsdag 27 mei 2003 21:35
> To: dev...@li...
> Subject: Re: [Dev-C++] Question about pointers (beginner)
>
>
> Christian Schmidt wrote:
> > Given x =3D 123 and ptr_int =3D &x after that *ptr_int =3D 456 has
> been executed.
> > What is the value of x?
>
> If I implemented this, this is how I would do it:
>
> #include <stdio.h>
>
> main()
> {
>    int x, *ptr_int;
>
>    x =3D 123;         /* Given x =3D 123 */
>    ptr_int =3D &x;    /* and ptr_int =3D&x */
>    *ptr_int =3D 456;  /* after that *ptr_int =3D 456 has been executed =
*/
>    printf("%d",x);  /* What is the value of x? */
>    /* The answer is: 123 */
> }
>
> > This is how I see it:
> >
> > main ( )
> > {
> > int x, *ptr_int;
> >
> > *ptr_int =3D 456; /*This pointer is a null pointer at this moment
> right? */
> >
> > x =3D123;
> > ptr_int =3D &x; /* As x is just set to 123 and the statement
> *ptr_int =3D 456;
> > was executed before I would think *ptr_int would be 123 */
> >
> > }
>
> This is a *wrong* implementation of the example. The book does not stat=
e
> this. It states what I wrote above.
>
> And the reason why it does not segfault is only luck. *ptr_int is not
> NULL at the beginning! Variables are NOT initialised, it is up to you t=
o
> do that. *ptr_int just points to somewhere, and you only had luck, that
> using it didn't cause any trouble. Try setting ptr_int to NULL before
> you dereference it (*ptr_int). It will surely segfault then.
> You should always keep it in mind, that variables are NEVER initialised
> to a default value! You must have to do that!
>
> > But the books says the value of *ptr_int at the end is 456. How come?=
?
>
> The book is correct.
>
> --
> Greetings,
>    Bal=E1zs
>
>
>
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