how to allocate memory dyamically for multidimensional array

[bijax]

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

 

[Richard Heathfield]

bijax said:

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

This is a Frequently Asked Question. The comp.lang.c newsgroup has an
associated FAQ list, which you should have no trouble in finding, and which
will provide you with the answer you seek.

 

[Daniel Rudy]

At about the time of 9/18/2005 11:24 PM, bijax stated the following:

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

int main(void)
{
int a[2][4][5][5];

/* insert program logic here */


/* return to operating system */
return(0);
}

Storage space is allocated when it's declared. Be carefull of int,
depending on your machine, it can be either 16 or 32 bits wide.

 

[Richard Heathfield]

Daniel Rudy said:

At about the time of 9/18/2005 11:24 PM, bijax stated the following:

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

int main(void)
{
int a[2][4][5][5];

You missed the subject line, in which he says "dynamically".

/* insert program logic here */


/* return to operating system */
return(0);
}

Storage space is allocated when it's declared. Be carefull of int,
depending on your machine, it can be either 16 or 32 bits wide.

Or 17, or 19, or 31, or 37, or 41, or 43, or 47, or 53, or 59, or 61, or 67,
or any of a whole bunch of other integers greater than 15. I'd count them
all for you, only I'm running a little late.

 

[Barry Schwarz]

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

See the faq at http://www.eskimo.com/~scs/C-faq/top.html, particularly
section 6.16. It pays to read the whole thing.


<<Remove the del for email>>

 

[Zoran Cutura]

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

Many different ways!

Say you want an two-dim-array of 5x5 ints. You can allocate

int height = 5, width = 5;
int *a = malloc(height * width * sizeof *a);

and use it like:

a[2*width + 3] which would be a[2][3]

or you can

int **a = malloc(height * sizeof *a);
int i;
for(i=0; i < height; i++) {
a = malloc(width * sizeof *a);
}

which allows you to use
a[2][3];

There are other sollutions, choose whatever fits best to the problem.

Note: You should check the return value of malloc in any case.

 

[Michel Rouzic]

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

well, do this (let's say it's a multidimensionnal array of doubles):

double ****a;
int_8t ia, ib, ic;

a=malloc (2 * sizeof(double ***)); //you can replace 2 by a variable
of course
for (ia=0; ia<2; i++) //and here by the same variable
a[ia]=malloc (4 * sizeof(double **));
for (ib=0; ib<4; i++)
a[ia][ib]=malloc (5 * sizeof(double *));
for (ic=0; ic<5; ic++)
a[ia][ib][ic]=malloc (5* sizeof(double));

Correct me if I'm wrong but I don't think I made any mistake...

 

[Daniel Rudy]

At about the time of 9/18/2005 11:51 PM, Richard Heathfield stated the
following:

Daniel Rudy said:

At about the time of 9/18/2005 11:24 PM, bijax stated the following:

hi,
i am new to multidimensional array of c programming .pls help me
to solve out this

how to allocate memory for mutidimensional array?
i.e a[2][4] [5][5];

int main(void)
{
int a[2][4][5][5];

You missed the subject line, in which he says "dynamically".

I did miss that. In that case...

int *data;
....
....
....
data = malloc(2 * 4 * 5 * 5);
if (data = NULL) exit(-1); /* malloc failed if true */
....
....
(*data)[x * y * x + i] = value;

Or something like that...

Or 17, or 19, or 31, or 37, or 41, or 43, or 47, or 53, or 59, or 61, or 67,
or any of a whole bunch of other integers greater than 15. I'd count them
all for you, only I'm running a little late.

Now why would int have those weird sizes? What hardware out there uses
a 53 bits as it's machine word?