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Arrays in C programming - Single, Double & Multidimensional

Group of similar type of elements is known as array in programming world. Array can be of predefined or use defined data types.

Points to remember about Array

Array index always start with 0
Array length can be any positive int value
We can also create array of pointer
We can access any element by its index value
Array size can't in increased at runtime
Size of Array is sum of size of its all elements
We can create Array of any data type
Address of Array first element is the address of Array
Types of Array - Single, Double & Multidimensional

Declaration of integer Array

int arr[71];

Here "arr" is the array which can contain 71 elements of int type

Initialize Array

Direct Initialization
Initialization using user input
Initialization using loops

Direct Initialization of int Array

int arr[71];

int a[0] = 1;
int a[2] = 2;
int a[3] = 3;
int a[4] = 5;
-------------
-------------
arr[70] = 72;

a[0] is known as first element of array, arr[1] is known as second element of array. The last index of array would be n-1 i.e 70 here.

Initialize int Array using loop

Array can be initialized using any of three loop ( for, while, do while ).

#include <stdio.h>

int main()
{
    int arr[71];
    int i;
    
    for(i=0; i<71; i++){
        arr[i] = 1;
    }
   
    /* printing all of its elements */
    
    for(i=0; i<71; i++){
        printf(" %d ", arr[i]);
    }

    return 0;
}

Initialize int Array using user input

#include <stdio.h>

int main()
{
    int arr[2];
    int i;
    
    for(i=0; i<2; i++){
        scanf("%d",&arr[i]);
    }
   
    /* printing all of its elements */
    
    for(i=0; i<2; i++){
        printf(" %d ", arr[i]);
    }

    return 0;
}

Size of Array

Size of any data type ( predefined or user defined ) can be calculated using the C library operator "sizeof()". Please note it is not a function, it is operator.
If we want to calculate without this operator then we can do manually like if array size is 71 like in above example arr[71] then the size required is 71 * Size of each element. So if the size of int is 4 bytes then the size of "arr" would be 71 * 4 = 284 bytes. Hence the formula is Size of Array * Bytes required for each element.

Double Dimensional Array

The syntax to declare Double Dimensional Array is int arr[Rows][Columns] where Rows, Columns can be any positive number. The size of DD Array is ( (R * C) * Size_Each_Element). Similar to SDA DDA can also be declared of any data type.

Example 1 (Direct Initialization)

#include <stdio.h>

int main()
{
    int arr[2][2] = {1, 2, 3, 4};
    
    for(int i=0; i<2; i++)
    {
        for(int j=0; j<2; j++)
        {
            printf(" %d ",arr[i][j]);
        }    
        printf("\n");
    }
    return 0;
}

Example 2 on DDM (Initialization using for loop)

#include <stdio.h>

int main()
{
    int arr[2][2];
	int count = 1;
    
    for(int i=0; i<2; i++)
    {
        for(int j=0; j<2; j++)
        {
            arr[i][j] =  count++;
        }    
        
    }
	
	for(int i=0; i<2; i++)
    {
        for(int j=0; j<2; j++)
        {
            printf(" %d ", arr[i][j]);
        } 
        printf("\n");
        
    }
    return 0;
}

Example 2 on DDM (Initialization using user input)

#include <stdio.h>

int main()
{
    int arr[2][2];

    for(int i=0; i<2; i++)
    {
        for(int j=0; j<2; j++)
        {
            scanf("%d", &arr[i][j]); //input any value and press enter
        }   
    }
	
	for(int i=0; i<2; i++)
    {
        for(int j=0; j<2; j++)
        {
            printf(" %d ", arr[i][j]);
        } 
        printf("\n");
    }
    return 0;
}

Three Dimensional Array

A 3D array is array of 2D array. You can imagine 3D array using this image -

Direct Initialization of 3D Array

#include <stdio.h>

int main()
{
    int arr[2][3][3] = {
                        {
                        {1,2,3},
                        {4.5,6},
                        {7,8,9},
                        },
                        
                        {
                        {11,12,13},
                        {14,15,16},
                        {17,18,19},
                        },
                       };

    for(int table=0; table<2; table++){	
		for(int i=0; i<3; i++)
		{
			for(int j=0; j<3; j++)
			{
				printf(" %d ", arr[table][i][j]);
			} 
			printf("\n");
		}
        printf("\n");
	}
    return 0;
}

Initialization of 3D Array using user input

#include <stdio.h>

int main()
{
    int arr[2][3][3]; 

    for(int table=0; table<2; table++)
    {
    for(int i=0; i<3; i++)
    {
        for(int j=0; j<3; j++)
        {
            scanf("%d", &arr[table][i][j]);
        }   
    }
    }

    for(int table=0; table<2; table++)	
    {
	for(int i=0; i<3; i++)
    {
        for(int j=0; j<3; j++)
        {
            printf(" %d ", arr[table][i][j]);
        } 
        printf("\n");
    }
     printf("\n");    
    }
    
    return 0;
}

In C programming an array can have one, two, three, or even four or more dimensions. The maximum dimensions in any C program depends on which compiler is being used. However, More dimensions in an array means more data be stored, but also means greater difficulty in managing and understanding arrays.