Working with C++ Arrays

In handling numerous data..

In programming, one of the frequently arising problem is to handle numerous data of same type.

Consider this situation, you are taking a survey of 100 people and you have to store their age. To solve this problem in C++, you can create an integer array having 100 elements.

An array is a collection of data that holds fixed number of values of same type. For example:

int age[100];

Here, the age array can hold maximum of 100 elements of integer type.

The size and type of arrays cannot be changed after its declaration.

How to declare an array in C++?

dataType arrayName[arraySize];

For example,

float mark[5];

Here, we declared an array, mark, of floating-point type and size 5. Meaning, it can hold 5 floating-point values.

Few key notes:

• Arrays have 0 as the first index not 1. In this example, mark[0] is the first element.

• If the size of an array is n, to access the last element, (n-1) index is used. In this example, mark[4] is the last element.

• Suppose the starting address of mark[0] is 2120d. Then, the next address, a[1], will be 2124d, address of a[2] will be 2128d and so on. It's because the size of float is 4 bytes.

How to initialize an array in C++ programming?

It's possible to initialize an array during declaration. For example,

int mark[5] = {19, 10, 8, 17, 9};

Another method to initialize array during declaration:

int mark[] = {19, 10, 8, 17, 9};

Here,

mark[0] is equal to 19

mark[1] is equal to 10

mark[2] is equal to 8

mark[3] is equal to 17

mark[4] is equal to 9

How to insert and print array elements?

int mark[5] = {19, 10, 8, 17, 9}

// change 4th element to 9

mark[3] = 9;

// take input from the user and insert in third element

cin >> mark[2];

// take input from the user and insert in (i+1)th element

cin >> mark[i];

// print first element of the array

cout << mark[0];

// print ith element of the array

cout >> mark[i-1];

Example:

/* C++ program to store and calculate the sum of 5 numbers entered by the user using arrays. */

#include <iostream>

using namespace std;

int main()

{

int numbers[5], sum = 0;

cout << "Enter 5 numbers: ";

// Storing 5 number entered by user in an array

// Finding the sum of numbers entered

for (int i = 0; i < 5; ++i)

{

cin >> numbers[i];

sum += numbers[i];

}

cout << "Sum = " << sum << endl;

return 0;

}

SAMPLE OUTPUT:

Enter 5 numbers: 3

4

5

4

2

Sum = 18

Things to remember when working with arrays in C++

Suppose you declared an array of 10 elements. Let's say,

int testArray[10];

You can use the array members from testArray[0] to testArray[9].

If you try to access array elements outside of its bound, let's say testArray[14], the compiler may not show any error. However, this may cause unexpected output (undefined behavior).