Array in C

Array is like a Basket. We carried basket when we are going to market. In a basket we can store apple, banana, vegetables etc. Here array is same like basket.

In array we can store homogeneous (Similar type) type of data. An array is an indexed collection of homogeneous data element (value). Every value is store in array based on indexed. In array we can store multiple values.

Advantage of Array

• A single array variable can store multiple values.
• Managing multiple values become easy.
• Accessing elements of an array become easy using index.

Disadvantage of Array

• In array we cannot store heterogeneous data elements (Value).
• Once we create an array we cannot increase or decrease the size. So memory wastage is there.

Types of Arrays

Three types of array are in C language

• One or Single Dimensional Array
• 2D or Multi-Dimensional Array
• 3 Dimensional Array

Single Dimensional Array

In single dimensional array we can store only single data type value. Single variable but one [ ] subscript.

Example of one or single dimensional array

    int a[10];
    float b[10];
    char c[10];

2D or Multi-Dimensional Array

In 2D or multi-dimensional array we can store multiple data value with single variable but multiple [ ] [ ] subscript. Array brackets are called subscript.

Example of 2D or multi-dimensional array

    int a[2][2] = {{5,6}, {8,3}}; 	//first value for row and second value for column.
    float b[2][2] = {{5,6}, {8,3}};
    char c[2][2] = {{5,6}, {8,3}};

3 Dimensional Array

Very rare case people use 3 Dimensional Array. Mostly we use 1D or 2D array in C.

Declaration of 1D or single dimensional array.

Syntax of array:

    data_type variable_name [size_of_array/index];

Example of array declaration:

    int a[5];
    float a[5];
    char ch[20];
    double d[10];
    

Invalid array declaration:

	
    int a[];	//invalid array declaration(size manadatory)
    
    int a[-5];	//invalid (size cannot be - negative)
    
    int i=10;
    int a[i]; //invalid (constant expression required at declaration time)

Working of Array

• Array index always start from 0
• If value is not entered in the array by default we get garbage value.
• One special memory created for array.
• Array variable hold or store the base address.
• Base is nothing but first starting index address.
• Size of array mandatory

Initialization of Array

In two ways we can initialize the Array.

• Compile time Initialization
• Runtime Initialization

Compile time Initialization

Further there are two types of compile time initialization.

• Multiline Initialization
• Single line Initialization

Example of multiline Initialization:

	
    int a[5];
    
        a[0];
        a[1];
        a[2];
        a[3];
        a[4];        
    

Example of single line initialization:

	int a[5] = {1,2,3,4,5};	//mostly we use single line initialization.

Valid or invalid array initialization

    int a[] = {1,2,3,4,5};	//Valid in single line initialization
    
    int a[5] = {1,2,3};		//remaining all value become zero like 4,5 missing
    
    int a[5] = {1,2,3,4,5,6};	//invalid initialization
    //because array size is 5 and we are entering 6 values
    
    int a[50] = 100; //invalid but valid in c
    //because c doesn't have strong boundary check

Runtime Array initialization:

In runtime array initialization we initialize the value to the array or size to the array at runtime through console window. We asking the value from user.

Example of runtime value initialization:

	#include<stdio.h>
	#include<conio.h>

	void main()
		{
		int a[]5;
		int i;
		clrscr();
   		printf("Enter the Value of array.\n");
		for(i=0;i<5;i++)
		{
		scanf("%d",&a[i]);
		}
		getch();
	}

Output:

    Enter the value of array.
    2
    3
    4
    5
    6

How to access the element of array?

We can access the element of array in two ways.

• One by one array element.
• Whole array element.

Example of whole array element accessing:

	#include<stdio.h>
	#include<conio.h>

	void main()
	{
		int a[5] ={1,2,3,4,5};
		int i;
		clrscr();
    	printf("Element of array:-\n");
		for(i=0;i<5;i++)
		{
		printf("%d\n",a[i]);
		}
		getch();
	}
    

Output:

    Element of array:-
    1
    2
    3
    4
    5
    

Example of one by one array element accessing:

	#include
	#include

	void main()
	{
		int a[5] ={1,2,3,4,5};
		int i;
		clrscr();
		printf("Element of array:-%d",a[0]);
		printf("\nElement of array:-%d",a[1]);
		printf("\nElement of array:-%d",a[2]);
		printf("\nElement of array:-%d",a[3]);
		printf("\nElement of array:-%d",a[4]);
		getch();
	}
    

Output:

    Element of array:- 1
    Element of array:- 2
    Element of array:- 3
    Element of array:- 4
    Element of array:- 5