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An array in C is a collection of elements having the same data type. It also defines the continuous memory location of the variable and which can be referred to as a single variable.

Declaration of an Array

type variable_name[];

In the above example, type denotes the data type of the array and variable_name denotes the name of the array.

Examples of some basic Array of specific data type

int a[10];
float a[20];
double a[20];
char a[20];

How to declare and Initialize an Array in C

 int a[5]={8,56,34,57,78};
 int a[]= {3,5,6,8,9};
 float a[]={13.5,23.7,45.12,-34.4,-12.8};
 char a1[7]="Sumit"; 

Some Important points about array by taking the above example

• All array elements would be present in contiguous memory Locations.
• 4 bytes for the integer variable. If an array has 6 elements then it consumes total of 24 bytes of memory.
• Arrays indexing always starts from a[0].
• In the above Example of a C array, each array occupies indexes from a[0] to a[5].

In addition, below We have also mentioned some properties of an array. So please have a look over it.

Properties of An Array in C Program

An Array has the following properties

• Elements of an array should be of a similar data type.
• It takes memory a contiguous fashion.
• Array elements are stored in a continuous fashion so that they can be randomly accessed.

Now together with properties let’s have an eye on the advantages and disadvantages of an Array.

Advantage of C Array in C Program

1) Code Optimization: Data can be accessed with very less code.

2) Ease of traversing: Traversing of an Array is very easy with for loop.

3) Ease of sorting: We can easily sort Array elements.

4) Random Access: Also we can access elements randomly.

5) Data Structure Implementation: Array helps to implement various data structures like linked lists, stacks, queues, trees, graphs, etc.

6) Matrix Representation: With the help of 2 Array, Matrix can be represented.

Disadvantage of C Array

1). Time complexity: In insertion and deletion operations, Time complexity increases.

2). Memory Wastage: Because arrays are fixed in size so if no elements in an array, still it consumes all spaces.

3). Fixed In Size: Once you had declared the size of an array, it is not possible to increase it.

Array example in C

#include <stdio.h>
int main()
{
    int a=0;    
    int marks[4];
    marks[0]=60;    
    marks[1]=10;    
    marks[2]=44;    
    marks[3]=8;      
    for(a=0;a<4;a++){      
        printf("%d \n",marks[a]);    
    }
    return 0;
}

Output

60 
10 
44 
8

Types of Array in C

There are 2 types of C arrays

1. One dimensional array
2. Multi dimensional array
   • Two dimensional array
   • Three dimensional array
   • four dimensional array etc….

One Dimensional Array

This can be considered as array as a row, where elements are stored one after another.

Syntax

data-type arr_name[array_size]; 

data-type: It denotes the type of the elements in the array.

arr_name: Name of the array. It must be a valid identifier.

array_size: Number of elements an array can hold.

Example 1: 1D Array implementation In C

#include <stdio.h>
int main()
{
    int a=0;    
    int marks[4];
    marks[0]=10;    
    marks[1]=20;    
    marks[2]=30;    
    marks[3]=40;  
    marks[4]=50; 
    for(a=0;a<5;a++){      
        printf("%d \n",marks[a]);    
    }
    return 0;
}

Output

10 
20 
30 
40 
50

Example 2: 2-D Array implementation In C

#include <stdio.h>
int main()
{
    int i,j;
   int arr[2][2] = {10,20,30,40};
   for (i=0;i<2;i++)
   {
      for (j=0;j<2;j++)
      {
            printf("value of arr[%d] [%d] : %d\n",i,j,arr[i][j]);
      }
   }
   return 0;
}

Output

value of arr[0] [0] : 10
value of arr[0] [1] : 20
value of arr[1] [0] : 30
value of arr[1] [1] : 40

Example 3: 2-D Array implementation In C

#include <stdio.h>
int main()
{
    int i,j,arr[2][2];
    arr[0][0] = 10; 
    arr[0][1] = 20;
    arr[1][0] = 30;
    arr[1][1] = 40;
    for (i=0;i<2;i++)
    {
      for (j=0;j<2;j++)
      {
            printf("value of arr[%d] [%d] : %d\n",i,j,arr[i][j]);
      }
    }
    return 0;
}

Output

value of arr[0] [0] : 10
value of arr[0] [1] : 20
value of arr[1] [0] : 30
value of arr[1] [1] : 40