CBSE Class 12 Informatics Practices: Arrays Notes

ARRAYS :-

Array is a group of same data types variables which are referred by a common name. An array is a series of elements of the same type placed in contiguous memory locations that can be individually referenced by adding an index to a unique identifier.

Need for Arrays :-

Suppose we have to store roll number & marks of 50 students in a program , then in all we need 100 variable each having a different name. Now remembering and managing these 100 variables is not easy task and it will make the program a complex and notunderstandable program. But if we declare two array each having fifty elements one for roll numbers and another for marks. Now, we have only two names to remember. Elements of these array will be referred to as Arrayname[n], where n is the element number in in the array . Therefore arrays are very much useful in a case where quit many elements of the same data types need to be stored and processed. The element number s in parenthesis are called subscripts or index. The subscript, or index of an element designates its position in the array’s ordering. 

Types of Array :-

Arrays are of two types: 1. One-dimensional Arrays 2. Multi-dimensional Arrays (But we have to discussing only Two-dimensional arrays in our syllabus

One –dimensional Arrays :-

The simplest form of an array is one - dimensional. The array itself is given a name and its elements are referred to by their subscripts. In C++ , an array must be defined before it can be used to store information. The general form of an array declaration is:Data_type Array_name[size]; For example the following statement declares an array marks of int data type , which have 50 elements marks[0] to marks[49]. int marks[50] ;

Referencing Array Elements:-

We can reference array elements by using the array’s name& subscript (or index). The first element has a subscript of 0. The last element in an array of length n has a subscript of n-1.

If we declare an array:

int scores[9];

then its 10 element will be referred as:

scores[0], scores[1], ……………………………….., scores[8]

Memory Representation of Single Dimensional Arrays:-

Elements of single dimensional array

are stored in contiguous memory location in their index order. For example , an array p of type

char with 6 elements declared as:

char p[6];

will be represented in memory as shown below: 

If we declare an int array age with 5 elements as: int age[5];

Accepting Data in Array from User (Inputting Array elements) and Printing Array elements:-

Since we can refer to individual array elements using numbered indexes, it is very common for

programmers to use for (or any) loops when processing arrays.     

Program : A C++ program to read an array of 10 elements and print the sum of all elements of array:

#include <iostream.h>

void main() { int a[10], sum=0;

for(int j=0; j<10; j++) //loop for reading { cout<< “Enter Element “<< j+1<<”:”;

cin>> a[j]

sum=sum+a[j]`; } cout<<”Sum : “<<sum; } Program: Here’s another example of an array this program , invites the user to enter a series of six

values representing sales for each day of the week (excluding Sunday), and then calculates the

average sales 

#include <iostream.h>

void main() { const int SIZE = 6; //size of array

double sales[SIZE]; //array of 6 elements

double total = 0;

cout<< “Enter sales for 6 days ”; for(int j=0; j<SIZE; j++) //put figures in array

cin>> sales[j];

for(j=0; j<SIZE; j++) //read figures from array

total += sales[j]; //to find total

double average = total / SIZE; // find average

cout<< “Average = “ << average << endl; } Output:-

Enter sales for 6 days

352.64

867.70

781.32

867.35

746.21

189.45

Average = 634.11

Linear Search:-

In linear search, each element of the array is compared with the given item to be

searched for , one by one either the desired element is found or the end of the array is reached. 

#include<iostream.h>

void main( ) { int size, i, n, c=0;

cout<<”Enter the size of array:”

cin>>size;

int a[size];

cout<<”Enter the elements of Array: “; 58 for(i-0; i<size; i++) { cin>>a[i]; } cout<<” Enter the number to be search : “;

cin>>n ;

for (i=0; i<size; i++)

{ if (a[i]= =n) { c=1;

break; } }

if (c= =0)

cout<<” The number is not in the array.”;

else

cout<<” The Number is found and location of element is: “<<i+1: }

Initializing arrays.

When we declare an array, we have the possibility to assign initial values to each one of its

elements by enclosing the values in braces { }. Syntax for initialization of one-dimensional array

is: 

Data_type Array_name[sise] = { value list } ;

For example:

int num [5] = { 16, 2, 77, 40, 12071 };

This declaration would have created an array like this:

The amount of values between braces { } must not be larger than the number of elements that we

declare for the array between square brackets [ ].

C++ allows us to skip the size of the array in an array initialization statement ( by leaving the

square brackets empty [ ] ). In this case, the compiler will assume a size for the array equal to the

number of values given between braces { }:

int num [ ] = { 16, 2, 77, 40, 12071 };

After this declaration, the size of array num will be 5, since we have provided 5 initialization

values.

Program : Program to find the maximum and minimum of an array :

#include<iostream.h>

void main( ) { int arr[ ] = {10, 6 , -9 , 17 , 34 , 20 , 34 ,-2 ,92 ,22 };

int max = min = arr[0];

for(int i = 0 ; i<10 ; i++) { if(arr[i] < min)

min= arr[i];

if(arr[i] > max)

max = arr[i]; } cout<<”The minimum of all is : “ << min<<”and the maximum is : “ <<max; } String as an array:- C++ does not have a string data type rather it implements string as single

dimensional character array. A string is defined as a character array terminated by a null character

‘’. Hence to declare an array strg that holds a 10 character string, you would write :

char strg[11];

Program : Program to count total number of vowels present in a string : 

#include<iostream.h>

#include<stdio.h>

void main( ) { char string[35]; int count = 0;

cout<<”Input a string”;

gets(string); // library function in stdio.h to input a string

for(int i = 0 ; string[i] != ’’ ; i++) { if( string[i] = = ’a’ || string[i] = = ’e’ || string[i] = = ’o’ || string[i] = = ’u’ || string[i] = = ’i’ ||

string[i] = = ’A’ || string[i] = = ’E’ || string[i] = = ’O’ || string[i] = = ’U’ || string[i] == ’I’ ) { count++; } } } Two dimensional array : A two dimensional array is a continuous memory location holding similar type of data arranged in row and column format (like a matrix structure).Declaration of 2-D array:- The general syntax used for 2-Darray declaration is:

Data_type Array_name [R][C] ;

Where R represent number of rows and C represent number of columns in array.

For example,

int marks [3][5];

and, for example, the way to reference the second element vertically and fourth horizontally in an

expression would be:

marks[1][3]

Initialization of 2-D Array:- Two dimensional arrays are also initialize in the same way as single

dimensional array . e. g.,

int cube[5][2] = {1,1, 2,8,3,27,4,64,4,125 };

will initialize cube[0][0]=1, cube[0][1]=1, cube[1][0]=2, cube[1][1]=8 , cube[2][0]=3 and so on.

2-D array can also be initialized in unsized manner. However the first index can be skiped , the

second index must be given. e.g.,

int cube[ ][2] = {1,1, 2,8,3,27,4,64,4,125 };

is also valid

Accepting Data in 2-D Array from User (Inputting 2-D Array elements) and Printing 2-D Array

elements:- Since We must reference both, a row number and a column number to input or output

values in a two-dimensional array. So, we use a nested loop (generally nested for loop) , when

processing 2-D arrays.

Frequently asked questions

What is an array in C++?

An array in C++ is a collection of elements of the same data type stored in contiguous memory locations, accessed using a common name and an index.

Why are arrays needed in programming?

Arrays are needed to efficiently store and manage a large number of variables of the same data type, simplifying code and making it more understandable.

What are the types of arrays discussed?

The notes discuss one-dimensional arrays and two-dimensional arrays.

How are elements accessed in a one-dimensional array?

Elements are accessed using the array name followed by the index in square brackets, e.g., arrayName[index]. The first element has an index of 0.

How are strings represented in C++?

C++ implements strings as one-dimensional character arrays terminated by a null character ('\0').

How are two-dimensional arrays processed?

Two-dimensional arrays are typically processed using nested loops, one for rows and one for columns.

What is linear search?

Linear search is an algorithm where each element of an array is checked sequentially to find a specific item.