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What is Array?

In C language, array is a collection of similar data types. An array is defined as finite ordered collection of homogenous data, stored in contiguous memory locations.

Here the words :-

finite means data range must be defined.

ordered means data must be stored in continuous memory addresses.

homogenous means data must be of similar data type.

Array in C language is a collection or group of elements (data). All the elements of c array are homogeneous (similar). It has contiguous memory location.

Advantage of C Array :-

1) Code Optimization: Less code to the access the data.

2) Easy to traverse data: By using the for loop, we can retrieve the elements of an array easily.

3) Easy to sort data: To sort the elements of array, we need a few lines of code only.

4) Random Access: We can access any element randomly using the array.

Disadvantage of C Array :-

1) Fixed Size: we define at the time of declaration of array, we can't exceed the limit. So, it doesn't grow the size dynamically like LinkedList.

Declaring an Array :-

arrays must be declared before they are used.
data-type variable-name[array-size];
/* Example of array declaration */
int arr[10];

Here int is the data type, arr is the name of the array and 10 is the size of array. It means array arr can only contain 10 elements of int type.
Index of an array starts from 0 to size-1 i.e first element of arr array will be stored at arr[0] address and the last element will occupy arr[9].

Initialization of an Array :-

A simple way to initialize array is by index. Notice that array index starts from 0 and ends with [SIZE - 1].
After an array is declared it must be initialized. Otherwise, it will contain garbage value(any random value). An array can be initialized at either compile time or at runtime.

marks[0]=20;//initialization of array
marks[1]=50;
marks[2]=60;
marks[3]=75;
marks[4]=65;

#include<stdio.h>
int main(){
int i=0;
int marks[5];//declaration of array
marks[0]=80;//initialization of array
marks[1]=60;
marks[2]=70;
marks[3]=85;
marks[4]=75;
//traversal of array
for(i=0;i<5;i++){
printf("%d \n",marks[i]);
}//end of for loop
return 0;
}

Output :-

80
60
70
85
75

Compile time Array initialization :-

Compile time initialization of array elements is same as ordinary variable initialization. The general form of initialization of array is :
data-type array-name[size] = { list of values };
/* Here are a few examples */
int marks[4]={ 67, 87, 56, 77 }; // integer array initialization
float area[5]={ 23.4, 6.8, 5.5 }; // float array initialization
int marks[4]={ 67, 87, 56, 77, 59 }; // Compile time error

Compile time Array initialization :-

#include<stdio.h>
void main()
{
int i;
int arr[] = {2, 3, 4}; // Compile time array initialization
for(i = 0 ; i < 3 ; i++)
{
printf("%d\t",arr[i]);
}
}
Output
2 3 4

Runtime Array initialization :-

An array can also be initialized at runtime using scanf() function. This approach is usually used for initializing large arrays, or to initialize arrays with user specified values.
#include< void main()
{
int arr[4];
int i, j;
printf("Enter array element");
for(i = 0; i < 4; i++)
{
scanf("%d", &arr[i]); //Run time array initialization
}
for(j = 0; j < 4; j++)
{
printf("%d\n", arr[j]);
}
}

Declaration with Initialization :-

We can initialize the c array at the time of declaration. Let's see the code.
int marks[5]={20,30,40,50,60};

In such case, there is no requirement to define size. So it can also be written as the following code.
int marks[]={20,30,40,50,60};

#include<stdio.h>
int main(){
int i=0;
int marks[5]={20,30,40,50,60};//declaration and initialization of array
//traversal of array
for(i=0;i<5;i++){
printf("%d \n",marks[i]);
}
return 0;
}

Two Dimensional Array in C :-

C language supports multidimensional arrays. The simplest form of a multidimensional array is the two-dimensional array.
The two dimensional array in C language is represented in the form of rows and columns, also known as matrix. It is also known as array of arrays or list of arrays.
The two dimensional, three dimensional or other dimensional arrays are also known as multidimensional arrays.

data-type array-name[row-size][column-size]
/* Example */
int a[3][4];

Initialization of 2D Array

There are two ways to initialize a two Dimensional arrays during declaration.

int disp[2][4] = {
{10, 11, 12, 13},
{14, 15, 16, 17}
};

OR
int disp[2][4] = { 10, 11, 12, 13, 14, 15, 16, 17};

int arr[][3] = {
{0,0,0},
{1,1,1}
};
Note: We have not assigned any row value to our array in the above example. It means we can initialize any number of rows. But, we must always specify number of columns, else it will give a compile time error. Here, a 2*3 multi-dimensional matrix is created.

/* Valid declaration*/
int abc[2][2] = {1, 2, 3 ,4 }

/* Valid declaration*/
int abc[][2] = {1, 2, 3 ,4 }

/* Invalid declaration – you must specify second dimension*/
int abc[][] = {1, 2, 3 ,4 }

/* Invalid because of the same reason mentioned above*/
int abc[2][] = {1, 2, 3 ,4 }

Runtime initialization of a two dimensional Array

#include<stdio.h>
void main()
{
int arr[3][4];
int i, j, k;
printf("Enter array element");
for(i = 0; i < 3;i++)
{
for(j = 0; j < 4; j++)
{
scanf("%d", &arr[i][j]);
}
}
for(i = 0; i < 3; i++)
{
for(j = 0; j < 4; j++)
{
printf("%d", arr[i][j]);
}
}
}

#include<stdio.h>
int main(){
int i=0,j=0;
int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};
//traversing 2D array
for(i=0;i<4;i++){
for(j=0;j<3;j++){
printf("arr[%d] [%d] = %d \n",i,j,arr[i][j]);
}//end of j
}//end of i
return 0;
}

output :-

arr[0][0] = 1
arr[0][1] = 2
arr[0][2] = 3
arr[1][0] = 2
arr[1][1] = 3
arr[1][2] = 4
arr[2][0] = 3
arr[2][1] = 4
arr[2][2] = 5
arr[3][0] = 4
arr[3][1] = 5
arr[3][2] = 6

Passing Array to Function in C :-

To reuse the array operation, we can create functions that receives array as argument. To pass array in function, we need to write the array name only in the function call.
functionname(arrayname);//passing array

There are 3 ways to declare function that receives array as argument. :-

First way:
return_type function(type arrayname[])
Declaring blank subscript notation [] is the widely used technique.
Second way:
return_type function(type arrayname[SIZE])
Optionally, we can define size in subscript notation [].
Third way:
return_type function(type *arrayname)

passing array to function :-

#include<stdio.h>
int minarray(int arr[],int size){
int min=arr[0];
int i=0;
for(i=1;i if(min>arr[i]){
min=arr[i];
}
}//end of for
return min;
}//end of function
int main(){
int i=0,min=0;
int numbers[]={4,5,7,3,8,9};//declaration of array
min=minarray(numbers,6);//passing array with size
printf("minimum number is %d \n",min);
return 0;
}

output :-

minimum number is 3

Itechtuto

C Tutorials

Important Links

What is Array?

Advantage of C Array :-

Disadvantage of C Array :-

Declaring an Array :-

Initialization of an Array :-

Output :-

Compile time Array initialization :-

Compile time Array initialization :-

Runtime Array initialization :-

Declaration with Initialization :-

Two Dimensional Array in C :-

Initialization of 2D Array

Runtime initialization of a two dimensional Array

output :-

Passing Array to Function in C :-

There are 3 ways to declare function that receives array as argument. :-

passing array to function :-

output :-

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