The memory for the pointer array and the two-dimensional array elements is usually allocated separately using dynamic memory allocation functions, namely, malloc or calloc. A simplified function imatalloc given below allocates a regular integer matrix of size m x n to variable tmp of type int. and returns this pointer to the calling function. It is a best practice to initialize an array to zero or null while declaring, if we don’t assign any values to array. Example for C Arrays: int a10; // integer array; char b10; // character array i.e. String; Types of C arrays: There are 2 types of C arrays. They are, One dimensional array; Multi dimensional array Two dimensional array.

Since a pointer to type T is analogous to an array of type T, a pointer to a pointer (T**) is analogous to an array of type T*, i. e., an array of pointers to type T. Each element in this array of pointers can be used further to point to an array of type T. Thus, a pointer to a pointer can be used to represent two-dimensional arrays, as illustrated in Fig.

C Programming - Passing a multi-dimensional array to a function Posted on March 27, 2019 by Paul. In this article I will show you how to pass a multi-dimensional array as a parameter to a function in C. For simplicity, we will present only the case of 2D arrays, but same considerations will apply to a general, multi-dimensional, array.
The most correct type to use here would have been an array pointer to an array of double, double (.)heightwidth, but that one comes with mandatory ugly accessing (.array2D)ij. To avoid such ugliness, a common trick is to leave out the left-most dimension in the array pointer declaration, then we can access it as array2Dij which.

Observe that we have a lot of flexibility in allocating memory for two-dimensional arrays. Thus, we can allocate a rectangular matrix (Fig a), a lower/upper triangular matrix (Fig b) and a ragged matrix in which each row can have different number of elements (Fig c). The use of a pointer to a pointer in conjunction with dynamic memory allocation is advantageous over a static matrix as it allows the allocation of a two-dimensional array of desired size and shape, avoiding wastage of memory.

Note that when a pointer to a pointer is declared, the memory is allocated only for the pointer variable. The memory for the pointer array and the two-dimensional array elements is usually allocated separately using dynamic memory allocation functions, namely, malloc or calloc.

A simplified function imat_alloc given below allocates a regular integer matrix of size m x n to variable tmp of type int ** and returns this pointer to the calling function

int **imat_alloc(int m, int n)

{

int i;

int **tmp = (int**) malloc(m * sizeof(int *));

for(i = 0; i < m; i++)

tmp[i] = (int*) malloc(n * sizeof(int));

return tmp;

}

Note that the function return type is a pointer to a pointer to int, i.e., int ** and the function returns a value of correct type (as tmp is of type int ** ). First, malloc allocates memory form pointers (i. e., m* sizeof (int *)) and assigns the address of this block, after typecasting to int **, to variable tmp. Then a for loop is used to allocate memory for each row. The malloc function now allocates memory for n integers (i.e., n * sizeof (inti) and assigns the address of this block, after typecasting to int *, to the ith pointer tmp[i] . Finally, the value of tmp is returned.

As you have probably noticed, the error checking code has been omitted in imat_alloc function to keep the things simple and focus on memory allocation logic. Although this is okay for small programs, we should include the error handling code in actual applications. The modified function is given below.

/* allocate the memory for a dynamic matrix */

int **imat_alloc(int m, int n)

{

int i;

/* first allocate memory for pointer array */

int **tmp = (int**) malloc(m * sizeof(int *));

if (tmp NULL) {

printf(“Error: Out of memory …n”);

C# 2 Dimensional Array Example

exit(1);

}

/* allocate memory for matrix rows */

for(i = 0; i < m; i++) {

tmp[i] = (int*) malloc(n * sizeof(int));

if (tmp[i] NULL) {

printf (“Error: Out of memory …n”);

exit (1);

}

return tmp;

}

This function can be called from any function to allocate a matrix as shown below.

int **a;

a= imat_alloc(m, n);

Note that now we cannot simply use the free function (as in free (a))to free the memory allocated to a matrix as it will only free the memory allocated to the pointer array. The function imat_free to free an integer matrix is given below. Top notch 3b unit 6. It accepts two parameters: a pointer to the matrix and the number of rows. It first uses a for loop to free the memory allocated to matrix rows and then frees the memory allocated to the pointer array.

void imat_free(int **a, int m)

{

int i;

/* free the memory allocated to matrix rows */

One Dimensional Array Of Two Dimensional Array Is Called

for (i = 0; i < m; i++)

free(a[i]);

free(a); /* free the memory allocated to pointer array */

}

Illustrates pointers to one- and two-dimensional arrays

C# 2 Dimensional Array Example

One Dimensional Array Of Two Dimensional Array Is Called

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One Dimensional And Two Dimensional Array In C