Array in C: Tutorial with examples

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C Array is a collection of variables belongings to the same data type. You can store group of data of same data type in an array.

Array might be belonging to any of the data types
Array size must be a constant value.
Always, Contiguous (adjacent) memory locations are used to store array elements in memory.
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 a[10]; // integer array
char b[10]; // 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
- Three dimensional array
- four dimensional array etc…

1. One dimensional array in C:

Syntax : data-type arr_name[array_size];

Array declaration, initialization and accessing

Example

Array declaration syntax:
data_type arr_name [arr_size];Array initialization syntax:
data_type arr_name [arr_size]=(value1, value2, value3,….);Array accessing syntax:
arr_name[index];

Integer array example:

int age [5];
int age[5]={0, 1, 2, 3, 4};

age[0]; /*0 is accessed*/
age[1]; /*1 is accessed*/
age[2]; /*2 is accessed*/

Character array example:

char str[10];
char str[10]={‘H’,‘a’,‘i’};
(or)
char str[0] = ‘H’;
char str[1] = ‘a’;
char str[2] = ‘i;

str[0]; /*H is accessed*/
str[1]; /*a is accessed*/
str[2]; /*i is accessed*/

Example program for one dimensional array in C:

#include<stdio.h> 

int main() 
{ 
     int i; 
     int arr[5] = {10,20,30,40,50}; 
    
        // declaring and Initializing array in C 
        //To initialize all array elements to 0, use int arr[5]={0}; 
        /* Above array can be initialized as below also 
        arr[0] = 10; 
        arr[1] = 20; 
        arr[2] = 30; 
        arr[3] = 40;
        arr[4] = 50; */

     for (i=0;i<5;i++) 
     { 
         // Accessing each variable
         printf("value of arr[%d] is %d \n", i, arr[i]); 
      } 
 
}

#include<stdio.h>

int main()

{

int i;

int arr[5] = {10,20,30,40,50};

// declaring and Initializing array in C

//To initialize all array elements to 0, use int arr[5]={0};

/* Above array can be initialized as below also

arr[0] = 10;

arr[1] = 20;

arr[2] = 30;

arr[3] = 40;

arr[4] = 50; */

for (i=0;i<5;i++)

{

// Accessing each variable

printf("value of arr[%d] is %d \n", i, arr[i]);

}

Output:

value of arr[0] is 10

value of arr[1] is 20

value of arr[2] is 30

value of arr[3] is 40

value of arr[4] is 50

2. Two dimensional array in C:

Two dimensional array is nothing but array of array.
syntax : data_type array_name[num_of_rows][num_of_column];

Array declaration, initialization and accessing

Example

Array declaration syntax:
data_type arr_name [num_of_rows][num_of_column];Array initialization syntax:
data_type arr_name[2][2] = {{0,0},{0,1},{1,0},{1,1}};Array accessing syntax:
arr_name[index];

Integer array example:

int arr[2][2];
int arr[2][2] = {1,2, 3, 4};

arr [0] [0] = 1;
arr [0] ]1] = 2;
arr [1][0] = 3;
arr [1] [1] = 4;

Example program for two dimensional array in C:

#include<stdio.h>

int main()
{
   int i,j;
   // declaring and Initializing array
   int arr[2][2] = {10,20,30,40};
   /* Above array can be initialized as below also
      arr[0][0] = 10; // Initializing array
      arr[0][1] = 20;
      arr[1][0] = 30;
      arr[1][1] = 40; */
   for (i=0;i<2;i++)
   {
      for (j=0;j<2;j++)
      {
         // Accessing variables
         printf("value of arr[%d] [%d] : %d\n",i,j,arr[i][j]);
      }
   }
}

#include<stdio.h>

int main()

{

int i,j;

// declaring and Initializing array

int arr[2][2] = {10,20,30,40};

/* Above array can be initialized as below also

arr[0][0] = 10; // Initializing array

arr[0][1] = 20;

arr[1][0] = 30;

arr[1][1] = 40; */

for (i=0;i<2;i++)

{

for (j=0;j<2;j++)

{

// Accessing variables

printf("value of arr[%d] [%d] : %d\n",i,j,arr[i][j]);

}

OUTPUT:

value of arr[0] [0] is 10

value of arr[0] [1] is 20

value of arr[1] [0] is 30

value of arr[1] [1] is 40

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