Array In C++ programming object oriented programming

1
Array in C++
Ahmad Baryal
Saba Institute of Higher Education
Computer Science Faculty
Nov 04, 2024

2 Table of contents
 Introduction to Array
 Properties of Array
 Declaration of Array
 Initialization of Array
 Accessing an Element of an Array
 Traverse an Array
 Size of an Array
 Relation between Arrays and Pointers in C++
 Multidimensional Arrays
 Two Dimensional Array

3 C++ Arrays
 In C++, an array is a data structure that is used to store multiple values of similar data
types in a contiguous memory location.
 For example, if we have to store the marks of 4 or 5 students then we can easily store
them by creating 5 different variables but what if we want to store marks of 100
students or say 500 students then it becomes very challenging to create that
numbers of variable and manage them. Now, arrays come into the picture that can
do it easily by just creating an array of the required size.

4 Properties of Arrays in C++
• An Array is a collection of data of the same data type, stored at a contiguous
memory location.
• Indexing of an array starts from 0. It means the first element is stored at the 0th
index, the second at 1st, and so on.
• Elements of an array can be accessed using their indices.
• Once an array is declared its size remains constant throughout the program.
• An array can have multiple dimensions.
• The number of elements in an array can be determined using the sizeof
operator.
• We can find the size of the type of elements stored in an array by subtracting
adjacent addresses.

5 Array Declaration in C++
In C++, we can declare an array by simply specifying the data type first and
then the name of an array with its size.
data_type array_name[Size_of_array]; Example: int arr[5];
Here,
• int: It is the type of data to be stored in the array. We can also use other
data types such as char, float, and double.
• arr: It is the name of the array.
• 5: It is the size of the array which means only 5 elements can be stored in
the array.

6 Initialization of Array in C++
• In C++, we can initialize an array in many ways but we will discuss some
most common ways to initialize an array. We can initialize an array at the
time of declaration or after declaration.
1. Initialize Array with Values in C++
We have initialized the array with values. The values enclosed in curly braces ‘{}’ are
assigned to the array. Here, 1 is stored in arr[0], 2 in arr[1], and so on. Here the size of the
array is 5.
int arr[5] = {1, 2, 3, 4, 5};
2. Initialize Array with Values and without Size in C++
We have initialized the array with values but we have not declared the length of the
array, therefore, the length of an array is equal to the number of elements inside curly
braces.
int arr[] = {1, 2, 3, 4, 5};

7 Initialization of Array in C++
3. Initialize Array after Declaration (Using Loops)
We have initialized the array using a loop after declaring the array. This method is
generally used when we want to take input from the user or we cant to assign elements
one by one to each index of the array. We can modify the loop conditions or change
the initialization values according to requirements.
for (int i = 0; i < N; i++) {
arr[i] = value;
}
4. Initialize an array partially in C++
Here, we have declared an array ‘partialArray’ with size ‘5’ and with values ‘1’ and ‘2’
only. So, these values are stored at the first two indices, and at the rest of the indices ‘0’
is stored.
int partialArray[5] = {1, 2};

8 Accessing an Element of an Array in C++
Elements of an array can be accessed by specifying the name of the array, then the index of
the element enclosed in the array subscript operator []. For example, arr[i].
Example 1: The C++ Program to Illustrate How to Access Array Elements
int arr[3];
// Inserting elements in an array
arr[0] = 10;
arr[1] = 20;
arr[2] = 30;
// Accessing and printing elements of the array
cout << "arr[0]: " << arr[0] << endl;
cout << "arr[1]: " << arr[1] << endl;
cout << "arr[2]: " << arr[2] << endl;

9 Traverse an Array in C++
We can traverse over the array with the help of a loop using indexing in C++. First, we have
initialized an array ‘table_of_two’ with a multiple of 2. After that, we run a for loop from 0 to
9 because in an array indexing starts from zero. Therefore, using the indices we print all
values stored in an array.
Example 2: The C++ Program to Illustrate How to Traverse an Array
// Initialize the array
int table_of_two[10]
= { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 };
// Traverse the array using for loop
for (int i = 0; i < 10; i++) {
// Print the array elements using indexing
cout << table_of_two[i] << " ";
}

10 Size of an Array in C++
In C++, we do not have the length function as in Java to find array size but we can calculate
the size of an array using sizeof() operator trick. First, we find the size occupied by the whole
array in the memory and then divide it by the size of the type of element stored in the array.
This will give us the number of elements stored in the array.
data_type size = sizeof(Array_name) / sizeof(Array_name[index]);
Example 3: The C++ Program to Illustrate How to Find the Size of an Array
int arr[] = { 1, 2, 3, 4, 5 };
cout << "Size of arr[0]: " << sizeof(arr[0]) << endl;
cout << "Size of arr: " << sizeof(arr) << endl;
// Length of an array
int n = sizeof(arr) / sizeof(arr[0]);
cout << "Length of an array: " << n << endl;

11 Relation between Arrays and Pointers in C++
In C++, arrays and pointers are closely related to each other. The array name is treated as a
pointer that stored the memory address of the first element of the array. As we have
discussed earlier, In array elements are stored at contiguous memory locations that’s why we
can access all the elements of an array using the array name.
// Defining an array
int arr[] = { 1, 2, 3, 4 };
// Define a pointer
int* ptr = arr;
// Printing address of the arrary using array name
cout << "Memory address of arr: " << &arr << endl;
// Printing address of the array using ptr
cout << "Memory address of arr: " << ptr << endl;
Explanation:
In the above code, we first define
an array “arr” and then declare a
pointer “ptr” and assign the array
“arr” to it. We are able to assign arr
to ptr because arr is also a pointer.
After that, we print the memory
address of arr using reference
operator (&) and also print the
address stored in pointer ptr and
we can see arr and ptr, both stores
the same memory address.

12 Example 5: Printing Array Elements without Indexing in C++
We generally access and print the array elements using indexing. For example to access the
first element we use array_name[0]. We have discussed above that the array name is a
pointer that stored the address of the first element and array elements are stored at
contiguous locations. Now, we are going to access the elements of an array using the array
name only.
// Define an array
int arr[] = { 11, 22, 33, 44 };
// Print elements of an array
cout << "first element: " << *arr << endl;
cout << "Second element: " << *(arr + 1) << endl;
cout << "Third element: " << *(arr + 2) << endl;
cout << "fourth element: " << *(arr + 3) << endl;
Explanation
• In the above code, we first declared an array “arr”
with four elements. After that, we are printing the
array elements. Let’s discuss how we do it. We
discussed that the array name is a pointer that
stores the address of the first element of an array
so, to print the first element we have dereferenced
that pointer (*arr) using dereferencing
operator (*) which prints the data stored at that
address.
• To print the second element of an array we first
add 1 to arr which is equivalent to (address of arr +
size_of_one_element *1) that takes the pointer to
the address just after the first one and after that,
we dereference that pointer to print the second
element. Similarly, we print rest of the elements of
an array without using indexing.

13 Passing Array to Function in C++
To use arrays efficiently we should know how to pass arrays to function. We can pass arrays to
functions as an argument same as we pass variables to functions but we know that the array
name is treated as a pointer using this concept we can pass the array to functions as an
argument and then access all elements of that array using pointer.
1. Passing Array as a Pointer
In this method, we simply pass the array name in function call which means we pass the
address to the first element of the array. In this method, we can modify the array elements
within the function.
Syntax
return_type function_name ( data_type *array_name ) {
// set of statements
}

14 Passing Array as a Pointer Example
Explanation:
1.Function Definition:
void modifyArray(int* arr, int size): This function
takes an integer pointer (arr) and the size of the
array as parameters.
2. Array Modification:
arr[i] *= 2;: Inside the function, each element of
the array is modified. In this example, each
element is multiplied by 2.
3. Function Call:
modifyArray(myArray, 5);: The array myArray is
passed to the function modifyArray along with its
size (5).
4. Printing Modified Array:
The main function prints the modified array after
the function call.

2. Passing Array as an Unsized Array
In this method, the function accepts the array using a simple array declaration with no size as an argument.
Syntax: return_type function_name ( data_type array_name[] ) {
// set of statements }
Explanation:
1. Function Definition:
void modifyArray(int arr[], int size): This function
takes an integer array (arr) and the size of the
array as parameters.
arr[i] *= 3;: Inside the function, each element of
element is multiplied by 3.
3. Function Call:
modifyArray(myArray, 5);: The array myArray is
passed to the function modifyArray along with its
size (5).
the function call.

3. Passing Array as a Sized Array
In this method, the function accepts the array using a simple array declaration with size as an argument. We use this
method by sizing an array just to indicate the size of an array.
Syntax : return_type function_name(data_type array_name[size_of_array]){
// set of statements }
Explanation:
1. Function Definition:
void modifyArray(int arr[5]): This function takes an
integer array (arr) with a specified size of 5.
arr[i] += 5;: Inside the function, each element of
element is incremented by 5.
3. Function Call:
modifyArray(myArray);: The array myArray is
passed to the function modifyArray. The size is not
explicitly mentioned in the function call because
it is implicitly known from the array declaration.
the function call.

17 Multidimensional Arrays in C++
Arrays declared with more than one dimension are called multidimensional arrays. The most widely used
multidimensional arrays are 2D arrays and 3D arrays. These arrays are generally represented in the form of
rows and columns.
Multidimensional Array Declaration
Data_Type Array_Name[Size1][Size2]...[SizeN];
where,
Data_Type: Type of data to be stored in the array.
Array_Name: Name of the array.
Size1, Size2,…, SizeN: Size of each dimension.
Example of a 2D Array Declaration:

18 Two Dimensional Array in C++
 In C++, a two-dimensional array is a grouping of elements arranged in rows and columns.
Each element is accessed using two indices: one for the row and one for the column,
which makes it easy to visualize as a table or grid.
Syntax of 2D array: data_Type array_name[n][m];
Where,
n: Number of rows.
m: Number of columns.

19 Example: Program to Illustrate 2D Array
Explanation:
The provided C++ example initializes a 2D
array named matrix with integer values.
Using nested loops, it iterates through each
element of the array, accessing them with
the syntax matrix[i][j]. A placeholder
variable element is introduced to represent
each value during the iteration. The
program performs a generic print
operation for each element,
demonstrating the process of accessing
and displaying values in a 2D array. Finally,
it moves to a new line after printing each
row. The example aims to illustrate the
fundamental structure of processing and
printing elements in a 2D array in a concise
manner.

Array In C++ programming object oriented programming

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