c/c++ Pointers (Memory allocation in the system)

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Hi to everyone,

I have very basic doubt in Pointer.

I have declared a variable like this

C++

int **value;

Book Definition:

C++

value = &anotherpointer;

But I have used the same double pointer for storing data in two dimensional array.

I have given a sample code below:

C++

value = (int **) malloc(sizeof(int)*2);
value[0] = (int *)malloc(sizeof(int) *2);
value[1]= (int *)malloc(sizeof(int)*2);

This above syntax is working fine with my program.

Basically, i have tried to create a dynamic two dimensional array of size (2X2).

The above syntax of creating dynamic array works fine for all user defined and built-in data types.

Please let me know how memory will be allocated if i tried to create a dynamic structure pointer or other data types of size (example 10).

Please let me know whether i have used the pointer correctly or not?

And let me know the reason. Looking forward for your replies....

Posted 28-Aug-12 23:25pm

balasubramaniyan94

Updated 28-Aug-12 23:28pm

CPallini

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CPallini · Answer 1 · 2012-08-28T23:37:00

Yes, you may use a double pointer to store the address of another pointer as well for creating a matrix, the compiler won't complain. :-)

The memory you are going to use does actually depend on the malloc statements.

Plaese note:

balasubramaniyan94 wrote:
value = (int **) malloc(sizeof(int)*2);

The above line is wrong, it should be

C

value = (int **) malloc(sizeof(int *) * 2);

(You are lucky if, as often happens, sizeof(int) == sizeof(int *)).