How to access two dimensional array using pointers in C programming? Write a C program to input and print elements of a two dimensional array using pointers and functions.

**Example**

**Input**

Input elements in 3x3 matrix: 1 2 3 4 5 6 7 8 9

**Output**

Elements of 3x3 matrix: 1 2 3 4 5 6 7 8 9

## Required knowledge

Multi-dimensional array, Pointers, Pointers and Arrays, Functions

## How to access two dimensional array using pointers?

To access a two dimensional array using pointer, let us recall basics from one dimensional array. Since it is just an array of one dimensional array.

Suppose I have a pointer `array_ptr`

pointing at base address of one dimensional array. To access nth element of array using pointer we use `*(array_ptr + n)`

(where `array_ptr`

points to 0th element of array, `n`

is the nth element to access and nth element starts from 0).

Now we know two dimensional array is array of one dimensional array. Hence let us see how to access a two dimensional array through pointer.

Let us suppose a two-dimensional array

`int matrix[3][3];`

For the above array,

```
matrix => Points to base address of two-dimensional array.
Since array decays to pointer.
*(matrix) => Points to first row of two-dimensional array.
*(matrix + 0) => Points to first row of two-dimensional array.
*(matrix + 1) => Points to second row of two-dimensional array.
**matrix => Points to matrix[0][0]
*(*(matrix + 0)) => Points to matrix[0][0]
*(*(matrix + 0) + 0) => Points to matrix[0][0]
*(*matrix + 1) => Points to matrix[0][1]
*(*(matrix + 0) + 1) => Points to matrix[0][1]
*(*(matrix + 2) + 2) => Points to matrix[2][2]
```

Note:If you are not familiar with`*(matrix + 2)`

syntax then please give yourself time and learn pointer arithmetic in C.

I have tried to summarize two dimensional array access using pointer in below image.

## Program to access a two dimensional array using pointer

```
/**
* C program to access two dimensional array using pointer.
*/
#include <stdio.h>
#define ROWS 3
#define COLS 3
/* Function declaration to input and print two dimensional array */
void inputMatrix(int matrix[][COLS], int rows, int cols);
void printMatrix(int matrix[][COLS], int rows, int cols);
int main()
{
int matrix[ROWS][COLS];
int i, j;
/* Input elements in matrix */
printf("Enter elements in %dx%d matrix.\n", ROWS, COLS);
inputMatrix(matrix, ROWS, COLS);
/* Print elements in matrix */
printf("Elements of %dx%d matrix.\n", ROWS, COLS);
printMatrix(matrix, ROWS, COLS);
return 0;
}
/**
* Function to take input in two dimensional array (matrix)
* from user.
*
* @matrix 2D array to store input.
* @rows Total rows in 2D matrix.
* @cols Total columns in 2D matrix.
*/
void inputMatrix(int matrix[][COLS], int rows, int cols)
{
int i, j;
for(i = 0; i < rows; i++)
{
for(j = 0; j < cols; j++)
{
// (*(matrix + i) + j is equivalent to &matrix[i][j]
scanf("%d", (*(matrix + i) + j));
}
}
}
/**
* Function to display elements of two dimensional array (matrix)
* on console.
*
* @matrix 2D array to display as output.
* @rows Total rows in 2D matrix.
* @cols Total columns in 2D matrix.
*/
void printMatrix(int (*matrix)[COLS], int rows, int cols)
{
int i, j;
for (i = 0; i < rows; i++)
{
for (j = 0; j < cols; j++)
{
// *(*(matrix + i) + j) is equivalent to matrix[i][j]
printf("%d ", *(*(matrix + i) + j));
}
printf("\n");
}
}
```

Note:You can use any of the two notations`int matrix[][COLS]`

or`int (*matrix)[COLS]`

, to access two dimensional array using pointers. The first`int matrix[][COLS]`

is general array notation. Whereas`int (*matrix)[COLS]`

is a pointer to array.

Output

Enter elements in 3x3 matrix. 1 2 3 4 5 6 7 8 9 Elements of 3x3 matrix. 1 2 3 4 5 6 7 8 9

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