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.
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