Array in C

What is Array ?

An array is a collection of similar data items stored at contiguous memory locations and the array elements can be accessed randomly using index of that array. In simple word an array is a variable that can store multiple values of same data type.

Why do we need array ? 

We use variables to store data. But sometime when we store more than one data by declaring variables every time (like - x1, x2, x3...) it becomes complicated. And for this reason, we use Array, where we can store a large amount of data by declaring the variable only once.

How to declare an array ?

Syntax : 

data_type array_name[array_size];

Example :

// Here, we are declaring an array, eruditors, of integer type. And its size is 25.
// Array declaration by specifying size.

int eruditors[25];

// Array declaration by user specified size.

int n = 25;
int eruditors[n];

How to initialize an array?

//It is possible to initialize an array during declaration. For example,

int eruditors[5] = {35, 98, 48, 117, 56};

//We can also initialize an array without specifying the array size. The compiler knows its size is 3 as we are initializing it with 3 elements. For example,

int eruditors[] = {211, 101, 169};

Array Input/Output Program in C :

//Program to take 5 values from the user and store them in an array.
//Print the elements stored in the array.

#include <stdio.h>

int main() 
{
    int eruditors[5];

    printf("Enter 5 integers : ");
    for(int i = 0; i < 5; i++) 
    {
     	scanf("%d", &eruditors[i]);
    }

    printf("Displaying integers : ");
    for(int i = 0; i < 5; ++i) 
    {
     	printf("%d  ", eruditors[i]);
    }
    return 0;
}

Output :

Accessing Array Elements: 

A specific element in an array is accessed by an integer index. Array index starts with 0 and goes till size of Array minus 1.

int eruditors[] = {211, 101, 169}; 

//Here 211, 101 and 169 can be accessed by eruditors[0], eruditors[1] and eruditors[2] respectively.

How to Change Value of Array elements?

Syntax :

array_name[index] = new_value;

Example :

int eruditors[5] = {117, 104, 101, 98, 91}

//Make the value of the first element to 91 & the fifth element to 117

eruditors[0] = 91;
eruditors[4] = 117;

Key Points about Array : 

• ~ Arrays can be used to store collection of primitive data types such as int, float, double, char etc.
• ~ The size and type of an array cannot be changed once it is declared.
• ~ Arrays have 0 as the first index, not 1.
• ~ If the size of an array is n, to access the last element, the n-1 index is used.
• ~ All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.

Advantages of an Array in C : 

• ~ Random access of elements using array index.
• ~ Use of less line of code as it creates a single array of multiple elements.
• ~ Easy access to all the elements.
• ~ Traversal through the array becomes easy using a single loop.
• ~ Sorting becomes easy as it can be accomplished by writing less line of code.

Disadvantages of an Array in C : 

• ~ Allows a fixed number of elements to be entered which is decided at the time of declaration. Unlike a linked list, an array in C is not dynamic.
• ~ Insertion and deletion of elements can be costly since the elements are needed to be managed in accordance with the new memory allocation.