Arrays in C Programming

An array is an identifier that stores a set of similar data. In another way, arrays can be defined as a data structure that can store a fixed size data in a sequential order where the data in it are of the same type. While arrays can store multiple values, a variable can store only one value at a time. For example, an array can store all the days Monday to Sunday while an array can store only one day, like Monday.

Arrays can be either one dimensional or multi-dimensional. A one-dimensional array would store data of the kind, prime numbers between 1 and 100, all the weekdays, etc. Multidimensional arrays would data the kind, data stored in rows and columns, for an instance a matrix. Let us discuss each of them.

An array fills the memory space in a contiguous manner. Each element in it would be allocated equal space which can be accessed by a value known as the index.

One Dimensional Array

Let us assume an array of the size n as shown in the figure. For an array with n size, it would accommodate n+1 elements. Such arrays are known to be the one-dimensional arrays.

Element[0] Element[1] … … … Element[n-2] Element[n-1]

Declaring Arrays

Arrays are defined like the variables with its size mentioned in square brackets [] as.
Datatype arrayName[size];

Initializing Arrays

It is not possible to assign all the elements to an array at once. So the elements must be initialized as shown below:
int arr[5] = {1, 2, 3, 4, 4};

All the elements are enclosed between the curly braces and separated by commas.

Example 14: Write a program that takes the number of array elements, asks the user to enter the data and find the sum of it.
Sample Code:

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#include &lt;stdio.h&gt;

//arraysum.c by bhutanio.com

void main()

{

int n, i;

int sum=0;

printf("\nEnter the number of elements ");

scanf("%d", &amp;n);

int arr[n];

printf("\nEnter the array elements \n");

for(i=0; i&lt;n; i++)

scanf("%d", &amp;arr[i]);

for(i=0; i&lt;n; i++)

sum=sum+arr[i];

printf("\nSum of the elements: %d", sum);

}

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Two Dimensional Arrays

The simplest form of multi-dimensional arrays is the two dimensional (2-D) arrays. These arrays are like matrices. Like matrices, the entries are in rows and columns. An m by n matrix would look like:

Two-dimensional array by THE BHUTAN IO — Two-dimensional array

Declaring 2-D Arrays

To declare such arrays, we do like in the one-dimensional array but here we need two pairs of square braces to mention the number of rows and columns, like.

datatype Array_Name[rows] [columns];

For the matrix A that takes character elements (mentioned above):
char A[m][n];

Initializing 2-D Arrays

2-D arrays are initialized by assigning bracketed values for each rows. For example:

int A[3][3] = {{1, 2, 3} , {1, 1, 2}, {1, 2, 3}};

Or equivalently, it can be initialized as:

int A[3][3] = {1, 2, 3, 1, 1, 2, 1, 2, 3};

Accessing 2-D Arrays

The array elements are accessed by specifying the rows and columns of the element to be accessed in two pairs of square brackets. For example, if I am to get an integer number from array A at 0th row and 0th column:
int x = A[0][0];
Now the variable x has the value of the element in A[0][0].

Example 15: Assume matrix

A = [1 0 0, 0 1 0, 0 0 1]

Write a C program that prints all the elements with its row and column indexes, and print the element at A[1][1].
Sample Code

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#include &lt;stdio.h&gt;

//implementing 2d array by bhutanio.com

void main(){

int a[3][3] = {{1, 0, 0},

{0, 1, 0},

{0, 0, 1}

};

int b = a[1][1];

int i , j;

//for printing all the elements with indexes

for(i = 0; i&lt; 3; i++){

for(j = 0; j&lt; 3; j++){

printf("\na[%d][%d] = %d", i, j, a[i][j]);

}

//for printing element at a[1][1]

printf("\nThe element at a[1][1] is %d", b);

}