c/c++ question

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Hello
How can i put data in a specific address , let say i want to put the number 8 in address 2000

Thanking you all in advance

Posted 13-Jan-11 6:56am

tctc7

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5 solutions

Solution 1

int *pInt = (int *)2000;
*pInt = 8;

Regards
Espen Harlinn

Posted 13-Jan-11 7:02am

Espen Harlinn

Updated 13-Jan-11 8:21am

v2

Comments

tctc7 13-Jan-11 13:16pm

Thank you but
I've got an error in this line int *pInt = 2000; :

2 IntelliSense: a value of type "int" cannot be used to initialize an entity of type "int *"

Sergey Alexandrovich Kryukov 13-Jan-11 14:22pm

Nothing to do with IntelliSense....

Yes, Espen, it would not compile, unfortunately -- not a big deal, though. See my answer.

Espen Harlinn 13-Jan-11 14:23pm

Sorry - forgot to cast the intergaer value i.e. (int *)2000

fjdiewornncalwe 13-Jan-11 14:27pm

+5 Same reason as for SAKryukov's answer... Cheers.

Sergey Alexandrovich Kryukov 13-Jan-11 14:30pm

Thank you guys.
Damn C++!

Solution 5

Hi,

You got valid C answers.
C++ provides the placement new syntax for your goal:

C++

// Create an int of value val at address buffer with placement new
int* p = new (buffer) int(val);

For your question it would be:

C++

int* pad = new ((int*)0x2000) int(8);

cheers,
AR
Edit: added unparametered code.

Posted 14-Jan-11 4:47am

Alain Rist

Updated 14-Jan-11 11:09am

v2

Comments

Chris Meech 14-Jan-11 10:51am

What's the declaration of buffer look like?

Alain Rist 14-Jan-11 15:52pm

int* buffer = (int*) a_valid_address; :)

Solution 3

C++

int *pInt = (int*)2000;
*pInt = 8;

Of course you should be careful with address. This answers your question, but...

In a normal application, this statement is useless, because you almost never have any constant addresses constants. It can be the case in very old systems or with something more exotic like embedded controllers.

Posted 13-Jan-11 8:21am

Sergey Alexandrovich Kryukov

Updated 13-Jan-11 8:27am

v2

Comments

Espen Harlinn 13-Jan-11 14:25pm

5+ for remembering the cast :)

fjdiewornncalwe 13-Jan-11 14:26pm

I'm guessing that this gentleman is in an early class on pointers. Taking this into account, I like your answer being very clear and concise.

Sergey Alexandrovich Kryukov 13-Jan-11 14:32pm

Thank you.
Probably you're right about the classes. Who cares though...

Solution 6

you must read some programming book first. Don't try to do that. :)

Posted 14-Jan-11 5:33am

jk chan

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Nish Nishant · Accepted Answer · 2011-01-13T07:09:00

Solution 2

Espen's shown you how to do it. But you should not be putting data into arbitrary memory locations unless you are sure you know what you are doing. It's a known recipe for disaster to do that.

Posted 13-Jan-11 7:09am

Nish Nishant

Comments

Chris Meech 13-Jan-11 14:32pm

Nish's comments are quite valid. There is no explanation for why someone has one voted it.

Nish Nishant 13-Jan-11 14:37pm

Ironically it was someone with Gold status too :-)