C++ Functional Console Programming

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C++ Functional Console Programming

C++ Introduction

C++ Variables, Literals and Constants

In this tutorial, we will learn about variables, literals, and constants in C++ with the help of examples.

C++ Variables

In programming, a variable is a container (storage area) to hold data.

To indicate the storage area, each variable should be given a unique name (identifier). For example,

int age = 14;

Here, age is a variable of the int data type, and we have assigned an integer value 14 to it.

Note: The int data type suggests that the variable can only hold integers. Similarly, we can use the double data type if we have to store decimals and exponentials.

We will learn about all the data types in detail in the next tutorial.

The value of a variable can be changed, hence the name variable.

int age = 14;   // age is 14
age = 17;       // age is 17

Rules for naming a variable

• A variable name can only have alphabets, numbers, and the underscore _.
• A variable name cannot begin with a number.
• It is a preferred practice to begin variable names with a lowercase character. For example, name is preferable to Name.
• A variable name cannot be a keyword. For example, int is a keyword that is used to denote integers.
• A variable name can start with an underscore. However, it's not considered a good practice.

Note: We should try to give meaningful names to variables. For example, first_name is a better variable name than fn.

C++ Literals

Literals are data used for representing fixed values. They can be used directly in the code. For example: 1, 2.5, 'c' etc.

Here, 1, 2.5 and 'c' are literals. Why? You cannot assign different values to these terms.

Here's a list of different literals in C++ programming.

1. Integers

An integer is a numeric literal(associated with numbers) without any fractional or exponential part. There are three types of integer literals in C programming:

• decimal (base 10)
• octal (base 8)
• hexadecimal (base 16)

For example:

Decimal: 0, -9, 22 etc
Octal: 021, 077, 033 etc
Hexadecimal: 0x7f, 0x2a, 0x521 etc

In C++ programming, octal starts with a 0, and hexadecimal starts with a 0x.

2. Floating-point Literals

A floating-point literal is a numeric literal that has either a fractional form or an exponent form. For example:

-2.0

0.0000234

-0.22E-5

Note: E-5 = 10-5

3. Characters

A character literal is created by enclosing a single character inside single quotation marks. For example: 'a', 'm', 'F', '2', '}' etc.

4. Escape Sequences

Sometimes, it is necessary to use characters that cannot be typed or has special meaning in C++ programming. For example, newline (enter), tab, question mark, etc.

In order to use these characters, escape sequences are used.

5. String Literals

A string literal is a sequence of characters enclosed in double-quote marks. For example:

We will learn about strings in detail in the C++ string tutorial.

C++ Constants

In C++, we can create variables whose value cannot be changed. For that, we use the const keyword. Here's an example:

const int LIGHT_SPEED = 299792458;
LIGHT_SPEED = 2500 // Error! LIGHT_SPEED is a constant.

Here, we have used the keyword const to declare a constant named LIGHT_SPEED. If we try to change the value of LIGHT_SPEED, we will get an error.

A constant can also be created using the #define preprocessor directive. We will learn about it in detail in the C++ Macros tutorial.

C++ Data Types

In this tutorial, we will learn about basic data types such as int, float, char, etc. in C++ programming with the help of examples.

In C++, data types are declarations for variables. This determines the type and size of data associated with variables. For example,

int age = 13;

Here, age is a variable of type int. Meaning, the variable can only store integers of either 2 or 4 bytes.

C++ Fundamental Data Types

The table below shows the fundamental data types, their meaning, and their sizes (in bytes):

Now, let us discuss these fundamental data types in more detail.

1. C++ int

• The int keyword is used to indicate integers.
• Its size is usually 4 bytes. Meaning, it can store values from -2147483648 to 2147483647.
• For example,

int salary = 85000;

2. C++ float and double

• float and double are used to store floating-point numbers (decimals and exponentials).
• The size of float is 4 bytes and the size of double is 8 bytes. Hence, double has two times the precision of float. To learn more, visit C++ float and double.
• For example,

float area = 64.74;
double volume = 134.64534;

As mentioned above, these two data types are also used for exponentials. For example,

double distance = 45E12    // 45E12 is equal to 45*10^12

3. C++ char

• Keyword char is used for characters.
• Its size is 1 byte.
• Characters in C++ are enclosed inside single quotes ' '.
• For example,

char test = 'h';

Note: In C++, an integer value is stored in a char variable rather than the character itself. To learn more, visit C++ characters.

4. C++ wchar_t

• Wide character wchar_t is similar to the char data type, except its size is 2 bytes instead of 1.
• It is used to represent characters that require more memory to represent them than a single char.
• For example,

wchar_t test = L'ם'  // storing Hebrew character;

Notice the letter L before the quotation marks.

Note: There are also two other fixed-size character types char16_t and char32_t introduced in C++11.

5. C++ bool

• The bool data type has one of two possible values: true or false.
• Booleans are used in conditional statements and loops (which we will learn in later chapters).
• For example,

bool cond = false;

6. C++ void

• The void keyword indicates an absence of data. It means "nothing" or "no value".
• We will use void when we learn about functions and pointers.

Note: We cannot declare variables of the void type.

C++ Type Modifiers

We can further modify some of the fundamental data types by using type modifiers. There are 4 type modifiers in C++. They are:

1. signed
2. unsigned
3. short
4. long

We can modify the following data types with the above modifiers:

• int
• double
• char

C++ Modified Data Types List

Let's see a few examples.

long b = 4523232;
long int c = 2345342;
long double d = 233434.56343;
short d = 3434233; // Error! out of range
unsigned int a = -5;    // Error! can only store positive numbers or 0

Derived Data Types

Data types that are derived from fundamental data types are derived types. For example: arrays, pointers, function types, structures, etc.

We will learn about these derived data types in later tutorials.

C++ Basic Input/Output

In this tutorial, we will learn to use the cin object to take input from the user, and the cout object to display output to the user with the help of examples.

C++ Output

In C++, cout sends formatted output to standard output devices, such as the screen. We use the cout object along with the << operator for displaying output.

Example 1: String Output

#include <iostream>
using namespace std;

int main() {
    // prints the string enclosed in double quotes
    cout << "This is C++ Programming";
    return 0;
}

Run Code

Output

This is C++ Programming

How does this program work?

• We first include the iostream header file that allows us to display output.
• The cout object is defined inside the std namespace. To use the std namespace, we used the using namespace std; statement.
• Every C++ program starts with the main() function. The code execution begins from the start of the main() function.
• cout is an object that prints the string inside quotation marks " ". It is followed by the << operator.
• return 0; is the "exit status" of the main() function. The program ends with this statement, however, this statement is not mandatory.

Note: If we don't include the using namespace std; statement, we need to use std::cout instead of cout.

This is the preferred method as using the std namespace can create potential problems.

However, we have used the std namespace in our tutorials in order to make the codes more readable.

#include <iostream>

int main() {
    // prints the string enclosed in double quotes
    std::cout << "This is C++ Programming";
    return 0;
}

Run Code

Example 2: Numbers and Characters Output

To print the numbers and character variables, we use the same cout object but without using quotation marks.

#include <iostream>
using namespace std;

int main() {
    int num1 = 70;
    double num2 = 256.783;
    char ch = 'A';

    cout << num1 << endl;    // print integer
    cout << num2 << endl;    // print double
    cout << "character: " << ch << endl;    // print char
    return 0;
}

Run Code

Output

70
256.783
character: A

Notes:

• The endl manipulator is used to insert a new line. That's why each output is displayed in a new line.
• The << operator can be used more than once if we want to print different variables, strings and so on in a single statement. For example:

cout << "character: " << ch << endl;

C++ Input

In C++, cin takes formatted input from standard input devices such as the keyboard. We use the cin object along with the >> operator for taking input.

Example 3: Integer Input/Output

#include <iostream>
using namespace std;

int main() {
    int num;
    cout << "Enter an integer: ";
    cin >> num;   // Taking input
    cout << "The number is: " << num;
    return 0;
}

Run Code

Output

Enter an integer: 70
The number is: 70

In the program, we used

cin >> num;

to take input from the user. The input is stored in the variable num. We use the >> operator with cin to take input.

Note: If we don't include the using namespace std; statement, we need to use std::cin instead of cin.

C++ Taking Multiple Inputs

#include <iostream>
using namespace std;

int main() {
    char a;
    int num;

    cout << "Enter a character and an integer: ";
    cin >> a >> num;

    cout << "Character: " << a << endl;
    cout << "Number: " << num;

    return 0;
}

Run Code

Output

Enter a character and an integer: F
23
Character: F
Number: 23

C++ Type Conversion

In this tutorial, we will learn about the basics of C++ type conversion with the help of examples.

C++ allows us to convert data of one type to that of another. This is known as type conversion.

There are two types of type conversion in C++.

1. Implicit Conversion
2. Explicit Conversion (also known as Type Casting)

Implicit Type Conversion

The type conversion that is done automatically done by the compiler is known as implicit type conversion. This type of conversion is also known as automatic conversion.

Let us look at two examples of implicit type conversion.

Example 1: Conversion From int to double

// Working of implicit type-conversion

#include <iostream>
using namespace std;

int main() {
   // assigning an int value to num_int
   int num_int = 9;

   // declaring a double type variable
   double num_double;

   // implicit conversion
   // assigning int value to a double variable
   num_double = num_int;

   cout << "num_int = " << num_int << endl;
   cout << "num_double = " << num_double << endl;

   return 0;
}

Run Code

Output

num_int = 9
num_double = 9

In the program, we have assigned an int data to a double variable.

num_double = num_int;

Here, the int value is automatically converted to double by the compiler before it is assigned to the num_double variable. This is an example of implicit type conversion.

Example 2: Automatic Conversion from double to int

//Working of Implicit type-conversion

#include <iostream>
using namespace std;

int main() {

   int num_int;
   double num_double = 9.99;

   // implicit conversion
   // assigning a double value to an int variable
   num_int = num_double;

   cout << "num_int = " << num_int << endl;
   cout << "num_double = " << num_double << endl;

   return 0;
}

Run Code

Output

num_int = 9
num_double = 9.99

In the program, we have assigned a double data to an int variable.

num_int = num_double;

Here, the double value is automatically converted to int by the compiler before it is assigned to the num_int variable. This is also an example of implicit type conversion.

Note: Since int cannot have a decimal part, the digits after the decimal point are truncated in the above example.

Data Loss During Conversion (Narrowing Conversion)

As we have seen from the above example, conversion from one data type to another is prone to data loss. This happens when data of a larger type is converted to data of a smaller type.

Possible Data Loss During Type Conversion

C++ Explicit Conversion

When the user manually changes data from one type to another, this is known as explicit conversion. This type of conversion is also known as type casting.

There are three major ways in which we can use explicit conversion in C++. They are:

1. C-style type casting (also known as cast notation)
2. Function notation (also known as old C++ style type casting)
3. Type conversion operators

C-style Type Casting

As the name suggests, this type of casting is favored by the C programming language. It is also known as cast notation.

The syntax for this style is:

(data_type)expression;

For example,

// initializing int variable
int num_int = 26;

// declaring double variable
double num_double;

// converting from int to double
num_double = (double)num_int;

Function-style Casting

We can also use the function like notation to cast data from one type to another.

The syntax for this style is:

data_type(expression);

For example,

// initializing int variable
int num_int = 26;

// declaring double variable
double num_double;

// converting from int to double
num_double = double(num_int);

Example 3: Type Casting

#include <iostream>

using namespace std;

int main() {
    // initializing a double variable
    double num_double = 3.56;
    cout << "num_double = " << num_double << endl;

    // C-style conversion from double to int
    int num_int1 = (int)num_double;
    cout << "num_int1   = " << num_int1 << endl;

    // function-style conversion from double to int
    int num_int2 = int(num_double);
    cout << "num_int2   = " << num_int2 << endl;

    return 0;
}

Run Code

Output

num_double = 3.56
num_int1   = 3
num_int2   = 3

We used both the C style type conversion and the function-style casting for type conversion and displayed the results. Since they perform the same task, both give us the same output.

Type Conversion Operators

Besides these two type castings, C++ also has four operators for type conversion. They are known as type conversion operators. They are:

• static_cast
• dynamic_cast
• const_cast
• reinterpret_cast

We will learn about these casts in later tutorials.

Recommended Tutorials:

• C++ string to int and Vice-versa
• C++ string to float, double and Vice-versa

C++ Operators

In this tutorial, we will learn about the different types of operators in C++ with the help of examples. In programming, an operator is a symbol that operates on a value or a variable.

Operators are symbols that perform operations on variables and values. For example, + is an operator used for addition, while - is an operator used for subtraction.

Operators in C++ can be classified into 6 types:

1. Arithmetic Operators
2. Assignment Operators
3. Relational Operators
4. Logical Operators
5. Bitwise Operators
6. Other Operators

1. C++ Arithmetic Operators

Arithmetic operators are used to perform arithmetic operations on variables and data. For example,

a + b;

Here, the + operator is used to add two variables a and b. Similarly there are various other arithmetic operators in C++.

Example 1: Arithmetic Operators

#include <iostream>
using namespace std;

int main() {
    int a, b;
    a = 7;
    b = 2;

    // printing the sum of a and b
    cout << "a + b = " << (a + b) << endl;

    // printing the difference of a and b
    cout << "a - b = " << (a - b) << endl;

    // printing the product of a and b
    cout << "a * b = " << (a * b) << endl;

    // printing the division of a by b
    cout << "a / b = " << (a / b) << endl;

    // printing the modulo of a by b
    cout << "a % b = " << (a % b) << endl;

    return 0;
}

Run Code

Output

a + b = 9
a - b = 5
a * b = 14
a / b = 3
a % b = 1

Here, the operators +, - and * compute addition, subtraction, and multiplication respectively as we might have expected.

/ Division Operator

Note the operation (a / b) in our program. The / operator is the division operator.

As we can see from the above example, if an integer is divided by another integer, we will get the quotient. However, if either divisor or dividend is a floating-point number, we will get the result in decimals.

In C++,

7/2 is 3
7.0 / 2 is 3.5
7 / 2.0 is 3.5
7.0 / 2.0 is 3.5

% Modulo Operator

The modulo operator % computes the remainder. When a = 9 is divided by b = 4, the remainder is 1.

Note: The % operator can only be used with integers.

Increment and Decrement Operators

C++ also provides increment and decrement operators: ++ and -- respectively.

• ++ increases the value of the operand by 1
• -- decreases it by 1

For example,

int num = 5;

// increment operator
++num;  // 6

Here, the code ++num; increases the value of num by 1.

Example 2: Increment and Decrement Operators

// Working of increment and decrement operators

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 100, result_a, result_b;

    // incrementing a by 1 and storing the result in result_a
    result_a = ++a;
    cout << "result_a = " << result_a << endl;


    // decrementing b by 1 and storing the result in result_b   
    result_b = --b;
    cout << "result_b = " << result_b << endl;

    return 0;
}

Run Code

Output

result_a = 11
result_b = 99

In the above program, we have used the ++ and -- operators as prefixes (++a and --b). However, we can also use these operators as postfix (a++ and b--).

To learn more, visit increment and decrement operators.

2. C++ Assignment Operators

In C++, assignment operators are used to assign values to variables. For example,

// assign 5 to a
a = 5;

Here, we have assigned a value of 5 to the variable a.

Example 3: Assignment Operators

#include <iostream>
using namespace std;

int main() {
    int a, b;

    // 2 is assigned to a
    a = 2;

    // 7 is assigned to b
    b = 7;

    cout << "a = " << a << endl;
    cout << "b = " << b << endl;
    cout << "\nAfter a += b;" << endl;

    // assigning the sum of a and b to a
    a += b;  // a = a +b
    cout << "a = " << a << endl;

    return 0;
}

Run Code

Output

a = 2
b = 7
After a += b;
a = 9

3. C++ Relational Operators

A relational operator is used to check the relationship between two operands. For example,

// checks if a is greater than b
a > b;

Here, > is a relational operator. It checks if a is greater than b or not.

If the relation is true, it returns 1 whereas if the relation is false, it returns 0.

Example 4: Relational Operators

#include <iostream>
using namespace std;

int main() {
    int a, b;
    a = 3;
    b = 5;
    bool result;

    result = (a == b);   // false
    cout << "3 == 5 is " << result << endl;

    result = (a != b);  // true
    cout << "3 != 5 is " << result << endl;

    result = a > b;   // false
    cout << "3 > 5 is " << result << endl;

    result = a < b;   // true
    cout << "3 < 5 is " << result << endl;

    result = a >= b;  // false
    cout << "3 >= 5 is " << result << endl;

    result = a <= b;  // true
    cout << "3 <= 5 is " << result << endl;

    return 0;
}

Run Code

Output

3 == 5 is 0
3 != 5 is 1
3 > 5 is 0
3 < 5 is 1
3 >= 5 is 0
3 <= 5 is 1

Note: Relational operators are used in decision-making and loops.

4. C++ Logical Operators

Logical operators are used to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0.

In C++, logical operators are commonly used in decision making. To further understand the logical operators, let's see the following examples,

Suppose,
a = 5
b = 8

Then,

(a > 3) && (b > 5) evaluates to true
(a > 3)  && (b < 5) evaluates to false

(a > 3) || (b > 5) evaluates to true
(a > 3) || (b < 5) evaluates to true
(a < 3) || (b < 5) evaluates to false

!(a < 3) evaluates to true
!(a > 3) evaluates to false

Example 5: Logical Operators

#include <iostream>
using namespace std;

int main() {
    bool result;

    result = (3 != 5) && (3 < 5);     // true
    cout << "(3 != 5) && (3 < 5) is " << result << endl;

    result = (3 == 5) && (3 < 5);    // false
    cout << "(3 == 5) && (3 < 5) is " << result << endl;

    result = (3 == 5) && (3 > 5);    // false
    cout << "(3 == 5) && (3 > 5) is " << result << endl;

    result = (3 != 5) || (3 < 5);    // true
    cout << "(3 != 5) || (3 < 5) is " << result << endl;

    result = (3 != 5) || (3 > 5);    // true
    cout << "(3 != 5) || (3 > 5) is " << result << endl;

    result = (3 == 5) || (3 > 5);    // false
    cout << "(3 == 5) || (3 > 5) is " << result << endl;

    result = !(5 == 2);    // true
    cout << "!(5 == 2) is " << result << endl;

    result = !(5 == 5);    // false
    cout << "!(5 == 5) is " << result << endl;

    return 0;
}

Run Code

Output

(3 != 5) && (3 < 5) is 1
(3 == 5) && (3 < 5) is 0
(3 == 5) && (3 > 5) is 0
(3 != 5) || (3 < 5) is 1
(3 != 5) || (3 > 5) is 1
(3 == 5) || (3 > 5) is 0
!(5 == 2) is 1
!(5 == 5) is 0

Explanation of logical operator program

• (3 != 5) && (3 < 5) evaluates to 1 because both operands (3 != 5) and (3 < 5) are 1 (true).
• (3 == 5) && (3 < 5) evaluates to 0 because the operand (3 == 5) is 0 (false).
• (3 == 5) && (3 > 5) evaluates to 0 because both operands (3 == 5) and (3 > 5) are 0 (false).
• (3 != 5) || (3 < 5) evaluates to 1 because both operands (3 != 5) and (3 < 5) are 1 (true).
• (3 != 5) || (3 > 5) evaluates to 1 because the operand (3 != 5) is 1 (true).
• (3 == 5) || (3 > 5) evaluates to 0 because both operands (3 == 5) and (3 > 5) are 0 (false).
• !(5 == 2) evaluates to 1 because the operand (5 == 2) is 0 (false).
• !(5 == 5) evaluates to 0 because the operand (5 == 5) is 1 (true).

5. C++ Bitwise Operators

In C++, bitwise operators are used to perform operations on individual bits. They can only be used alongside char and int data types.

To learn more, visit C++ bitwise operators.

6. Other C++ Operators

Here's a list of some other common operators available in C++. We will learn about them in later tutorials.

C++ Comments

In this tutorial, we will learn about C++ comments, why we use them, and how to use them with the help of examples.

C++ comments are hints that a programmer can add to make their code easier to read and understand. They are completely ignored by C++ compilers.

There are two ways to add comments to code:

// - Single Line Comments

/* */ -Multi-line Comments

Single Line Comments

In C++, any line that starts with // is a comment. For example,

// declaring a variable
int a;

// initializing the variable 'a' with the value 2
a = 2;

Here, we have used two single-line comments:

• // declaring a variable
• // initializing the variable 'a' with the value 2

We can also use single line comment like this:

int a;    // declaring a variable

Multi-line comments

In C++, any line between /* and */ is also a comment. For example,

/* declaring a variableto store salary to employees*/
int salary = 2000;

This syntax can be used to write both single-line and multi-line comments.

Using Comments for Debugging

Comments can also be used to disable code to prevent it from being executed. For example,

#include <iostream>
using namespace std;
int main() {
   cout << "some code";
   cout << ''error code;   cout << "some other code";   return 0;}

Run Code

If we get an error while running the program, instead of removing the error-prone code, we can use comments to disable it from being executed; this can be a valuable debugging tool.

#include <iostream>
using namespace std;
int main() {
   cout << "some code";
   // cout << ''error code;
   cout << "some other code";

   return 0;
}

Run Code

Pro Tip: Remember the shortcut for using comments; it can be really helpful. For most code editors, it's Ctrl + / for Windows and Cmd + / for Mac.

Why use Comments?

If we write comments on our code, it will be easier for us to understand the code in the future. Also, it will be easier for your fellow developers to understand the code.

Note: Comments shouldn't be the substitute for a way to explain poorly written code in English. We should always write well-structured and self-explanatory code. And, then use comments.

As a general rule of thumb, use comments to explain Why you did something rather than How you did something, and you are good.

C++ Flow Control

C++ if, if...else and Nested if...else

In this tutorial, we will learn about the if...else statement to create decision making programs with the help of examples.

In computer programming, we use the if...else statement to run one block of code under certain conditions and another block of code under different conditions.

For example, assigning grades (A, B, C) based on marks obtained by a student.

• if the percentage is above 90, assign grade A
• if the percentage is above 75, assign grade B
• if the percentage is above 65, assign grade C

There are three forms of if...else statements in C++.

1. if statement
2. if...else statement
3. if...else if...else statement

C++ if Statement

The syntax of the if statement is:

if (condition) {
  // body of if statement
}

The if statement evaluates the condition inside the parentheses ( ).

• If the condition evaluates to true, the code inside the body of if is executed.
• If the condition evaluates to false, the code inside the body of if is skipped.

Note: The code inside { } is the body of the if statement.

How if Statement Works

Example 1: C++ if Statement

// Program to print positive number entered by the user
// If the user enters a negative number, it is skipped

#include <iostream>
using namespace std;

int main() {

  int number;

  cout << "Enter an integer: ";
  cin >> number;

  // checks if the number is positive
  if (number > 0) {
    cout << "You entered a positive integer: " << number << endl;
  }

  cout << "This statement is always executed.";

  return 0;
}

Run Code

Output 1

Enter an integer: 5
You entered a positive number: 5
This statement is always executed.

When the user enters 5, the condition number > 0 is evaluated to true and the statement inside the body of if is executed.

Output 2

Enter a number: -5
This statement is always executed.

When the user enters -5, the condition number > 0 is evaluated to false and the statement inside the body of if is not executed.

C++ if...else

The if statement can have an optional else clause. Its syntax is:

if (condition) {
  // block of code if condition is true
}
else {
  // block of code if condition is false
}

The if..else statement evaluates the condition inside the parenthesis.

How if...else Statement Works

If the condition evaluates true,

• the code inside the body of if is executed
• the code inside the body of else is skipped from execution

If the condition evaluates false,

• the code inside the body of else is executed
• the code inside the body of if is skipped from execution

Example 2: C++ if...else Statement

// Program to check whether an integer is positive or negative
// This program considers 0 as a positive number

#include <iostream>
using namespace std;

int main() {

  int number;

  cout << "Enter an integer: ";
  cin >> number;

  if (number >= 0) {
    cout << "You entered a positive integer: " << number << endl;
  }
  else {
    cout << "You entered a negative integer: " << number << endl;
  }

  cout << "This line is always printed.";

  return 0;
}

Run Code

Output 1

Enter an integer: 4
You entered a positive integer: 4.
This line is always printed.

In the above program, we have the condition number >= 0. If we enter the number greater or equal to 0, then the condition evaluates true.

Here, we enter 4. So, the condition is true. Hence, the statement inside the body of if is executed.

Output 2

Enter an integer: -4
You entered a negative integer: -4.
This line is always printed.

Here, we enter -4. So, the condition is false. Hence, the statement inside the body of else is executed.

C++ if...else...else if statement

The if...else statement is used to execute a block of code among two alternatives. However, if we need to make a choice between more than two alternatives, we use the if...else if...else statement.

The syntax of the if...else if...else statement is:

if (condition1) {
  // code block 1
}
else if (condition2){
  // code block 2
}
else {
  // code block 3
}

Here,

• If condition1 evaluates to true, the code block 1 is executed.
• If condition1 evaluates to false, then condition2 is evaluated.
• If condition2 is true, the code block 2 is executed.
• If condition2 is false, the code block 3 is executed.

How if...else if...else Statement Works

Note: There can be more than one else if statement but only one if and else statements.

Example 3: C++ if...else...else if

// Program to check whether an integer is positive, negative or zero

#include <iostream>
using namespace std;

int main() {

  int number;

  cout << "Enter an integer: ";
  cin >> number;

  if (number > 0) {
    cout << "You entered a positive integer: " << number << endl;
  } 
  else if (number < 0) {
    cout << "You entered a negative integer: " << number << endl;
  } 
  else {
    cout << "You entered 0." << endl;
  }

  cout << "This line is always printed.";

  return 0;
}

Run Code

Output 1

Enter an integer: 1
You entered a positive integer: 1.
This line is always printed.

Output 2

Enter an integer: -2
You entered a negative integer: -2.
This line is always printed.

Output 3

Enter an integer: 0
You entered 0.
This line is always printed.

In this program, we take a number from the user. We then use the if...else if...else ladder to check whether the number is positive, negative, or zero.

If the number is greater than 0, the code inside the if block is executed. If the number is less than 0, the code inside the else if block is executed. Otherwise, the code inside the else block is executed.

C++ Nested if...else

Sometimes, we need to use an if statement inside another if statement. This is known as nested if statement.

Think of it as multiple layers of if statements. There is a first, outer if statement, and inside it is another, inner if statement. Its syntax is:

// outer if statement
if (condition1) {

  // statements

  // inner if statement
  if (condition2) {
    // statements
  }
}

Notes:

• We can add else and else if statements to the inner if statement as required.
• The inner if statement can also be inserted inside the outer else or else if statements (if they exist).
• We can nest multiple layers of if statements.

Example 4: C++ Nested if

// C++ program to find if an integer is positive, negative or zero
// using nested if statements

#include <iostream>
using namespace std;

int main() {

  int num;

  cout << "Enter an integer: ";  
   cin >> num;    

  // outer if condition
  if (num != 0) {

    // inner if condition
    if (num > 0) {
      cout << "The number is positive." << endl;
    }
    // inner else condition
    else {
      cout << "The number is negative." << endl;
    }  
  }
  // outer else condition
  else {
    cout << "The number is 0 and it is neither positive nor negative." << endl;
  }

  cout << "This line is always printed." << endl;

  return 0;
}

Run Code

Output 1

Enter an integer: 35
The number is positive.
This line is always printed.

Output 2

Enter an integer: -35
The number is negative.
This line is always printed.

Output 3

Enter an integer: 0
The number is 0 and it is neither positive nor negative.
This line is always printed.

In the above example,

• We take an integer as an input from the user and store it in the variable num.
• We then use an if...else statement to check whether num is not equal to 0.
  • If true, then the inner if...else statement is executed.
  • If false, the code inside the outer else condition is executed, which prints "The number is 0 and it is neither positive nor negative."
• The inner if...else statement checks whether the input number is positive i.e. if num is greater than 0.
  • If true, then we print a statement saying that the number is positive.
  • If false, we print that the number is negative.

Note: As you can see, nested if...else makes your logic complicated. If possible, you should always try to avoid nested if...else.

Body of if...else With Only One Statement

If the body of if...else has only one statement, you can omit { } in the program. For example, you can replace

int number = 5;

if (number > 0) {
  cout << "The number is positive." << endl;
}
else {
  cout << "The number is negative." << endl;
}

with

int number = 5;

if (number > 0)
  cout << "The number is positive." << endl;
else
  cout << "The number is negative." << endl;

The output of both programs will be the same.

Note: Although it's not necessary to use { } if the body of if...else has only one statement, using { } makes your code more readable.

More on Decision Making

In certain situations, a ternary operator can replace an if...else statement. To learn more, visit C++ Ternary Operator.

If we need to make a choice between more than one alternatives based on a given test condition, the switch statement can be used. To learn more, visit C++ switch.

Check out these examples to learn more:

C++ Program to Check Whether Number is Even or Odd

C++ Program to Check Whether a character is Vowel or Consonant.

C++ Program to Find Largest Number Among Three Numbers

C++ for Loop

In this tutorial, we will learn about the C++ for loop and its working with the help of some examples.

In computer programming, loops are used to repeat a block of code.

For example, let's say we want to show a message 100 times. Then instead of writing the print statement 100 times, we can use a loop.

That was just a simple example; we can achieve much more efficiency and sophistication in our programs by making effective use of loops.

There are 3 types of loops in C++.

• for loop
• while loop
• do...while loop

This tutorial focuses on C++ for loop. We will learn about the other type of loops in the upcoming tutorials.

C++ for loop

The syntax of for-loop is:

for (initialization; condition; update) {
    // body of-loop 
}

Here,

• initialization - initializes variables and is executed only once
• condition - if true, the body of for loop is executed
  if false, the for loop is terminated
• update - updates the value of initialized variables and again checks the condition

To learn more about conditions, check out our tutorial on C++ Relational and Logical Operators.

Flowchart of for Loop in C++

Flowchart of for loop in C++

Example 1: Printing Numbers From 1 to 5

#include <iostream>

using namespace std;

int main() {
        for (int i = 1; i <= 5; ++i) {
        cout << i << " ";
    }
    return 0;
}

Run Code

Output

1 2 3 4 5

Here is how this program works

Example 2: Display a text 5 times

// C++ Program to display a text 5 times

#include <iostream>

using namespace std;

int main() {
    for (int i = 1; i <= 5; ++i) {
        cout <<  "Hello World! " << endl;
    }
    return 0;
}

Run Code

Output

Hello World!
Hello World!
Hello World!
Hello World!
Hello World!

Here is how this program works

Example 3: Find the sum of first n Natural Numbers

// C++ program to find the sum of first n natural numbers
// positive integers such as 1,2,3,...n are known as natural numbers

#include <iostream>

using namespace std;

int main() {
    int num, sum;
    sum = 0;

    cout << "Enter a positive integer: ";
    cin >> num;

    for (int i = 1; i <= num; ++i) {
        sum += i;
    }

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

    return 0;
}

Run Code

Output

Enter a positive integer: 10
Sum = 55

In the above example, we have two variables num and sum. The sum variable is assigned with 0 and the num variable is assigned with the value provided by the user.

Note that we have used a for loop.

for(int i = 1; i <= num; ++i)

Here,

• int i = 1: initializes the i variable
• i <= num: runs the loop as long as i is less than or equal to num
• ++i: increases the i variable by 1 in each iteration

When i becomes 11, the condition is false and sum will be equal to 0 + 1 + 2 + ... + 10.

Ranged Based for Loop

In C++11, a new range-based for loop was introduced to work with collections such as arrays and vectors. Its syntax is:

for (variable : collection) {
    // body of loop
}

Here, for every value in the collection, the for loop is executed and the value is assigned to the variable.

Example 4: Range Based for Loop

#include <iostream>

using namespace std;

int main() {

    int num_array[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    for (int n : num_array) {
        cout << n << " ";
    }

    return 0;
}

Run Code

Output

1 2 3 4 5 6 7 8 9 10

In the above program, we have declared and initialized an int array named num_array. It has 10 items.

Here, we have used a range-based for loop to access all the items in the array.

C++ Infinite for loop

If the condition in a for loop is always true, it runs forever (until memory is full). For example,

// infinite for loop
for(int i = 1; i > 0; i++) {
    // block of code
}

In the above program, the condition is always true which will then run the code for infinite times.

Check out these examples to learn more:

• C++ Program to Calculate Sum of Natural Numbers
• C++ Program to Find Factorial
• C++ Program to Generate Multiplication Table

In the next tutorial, we will learn about while and do...while loop.

C++ while and do...while Loop

In this tutorial, we will learn the use of while and do...while loops in C++ programming with the help of some examples.

In computer programming, loops are used to repeat a block of code.

For example, let's say we want to show a message 100 times. Then instead of writing the print statement 100 times, we can use a loop.

That was just a simple example; we can achieve much more efficiency and sophistication in our programs by making effective use of loops.

There are 3 types of loops in C++.

1. for loop
2. while loop
3. do...while loop

In the previous tutorial, we learned about the C++ for loop. Here, we are going to learn about while and do...while loops.

C++ while Loop

The syntax of the while loop is:

while (condition) {
    // body of the loop
}

Here,

• A while loop evaluates the condition
• If the condition evaluates to true, the code inside the while loop is executed.
• The condition is evaluated again.
• This process continues until the condition is false.
• When the condition evaluates to false, the loop terminates.

To learn more about the conditions, visit C++ Relational and Logical Operators.

Flowchart of while Loop

Flowchart of C++ while loop

Example 1: Display Numbers from 1 to 5

// C++ Program to print numbers from 1 to 5

#include <iostream>

using namespace std;

int main() {
    int i = 1; 

    // while loop from 1 to 5
    while (i <= 5) {
        cout << i << " ";
        ++i;
    }

    return 0;
}

Run Code

Output

1 2 3 4 5

Here is how the program works.

Example 2: Sum of Positive Numbers Only

// program to find the sum of positive numbers
// if the user enters a negative number, the loop ends
// the negative number entered is not added to the sum

#include <iostream>
using namespace std;

int main() {
    int number;
    int sum = 0;

    // take input from the user
    cout << "Enter a number: ";
    cin >> number;

    while (number >= 0) {
        // add all positive numbers
        sum += number;

        // take input again if the number is positive
        cout << "Enter a number: ";
        cin >> number;
    }

    // display the sum
    cout << "\nThe sum is " << sum << endl;

    return 0;
}

Run Code

Output

Enter a number: 6
Enter a number: 12
Enter a number: 7
Enter a number: 0
Enter a number: -2
The sum is 25

In this program, the user is prompted to enter a number, which is stored in the variable number.

In order to store the sum of the numbers, we declare a variable sum and initialize it to the value of 0.

The while loop continues until the user enters a negative number. During each iteration, the number entered by the user is added to the sum variable.

When the user enters a negative number, the loop terminates. Finally, the total sum is displayed.

C++ do...while Loop

The do...while loop is a variant of the while loop with one important difference: the body of do...while loop is executed once before the condition is checked.

Its syntax is:

do {
   // body of loop;
}
while (condition);

Here,

• The body of the loop is executed at first. Then the condition is evaluated.
• If the condition evaluates to true, the body of the loop inside the do statement is executed again.
• The condition is evaluated once again.
• If the condition evaluates to true, the body of the loop inside the do statement is executed again.
• This process continues until the condition evaluates to false. Then the loop stops.

Flowchart of do...while Loop

Flowchart of C++ do...while loop

Example 3: Display Numbers from 1 to 5

// C++ Program to print numbers from 1 to 5

#include <iostream>

using namespace std;

int main() {
    int i = 1; 

    // do...while loop from 1 to 5
    do {
        cout << i << " ";
        ++i;
    }
    while (i <= 5);

    return 0;
}

Run Code

Output

1 2 3 4 5

Here is how the program works.

Example 4: Sum of Positive Numbers Only

// program to find the sum of positive numbers
// If the user enters a negative number, the loop ends
// the negative number entered is not added to the sum

#include <iostream>
using namespace std;

int main() {
    int number = 0;
    int sum = 0;

    do {
        sum += number;

        // take input from the user
        cout << "Enter a number: ";
        cin >> number;
    }
    while (number >= 0);

    // display the sum
    cout << "\nThe sum is " << sum << endl;

    return 0;
}

Run Code

Output 1

Enter a number: 6
Enter a number: 12
Enter a number: 7
Enter a number: 0
Enter a number: -2
The sum is 25

Here, the do...while loop continues until the user enters a negative number. When the number is negative, the loop terminates; the negative number is not added to the sum variable.

Output 2

Enter a number: -6
The sum is 0.

The body of the do...while loop runs only once if the user enters a negative number.

Infinite while loop

If the condition of a loop is always true, the loop runs for infinite times (until the memory is full). For example,

// infinite while loop
while(true) {
    // body of the loop
}

Here is an example of an infinite do...while loop.

// infinite do...while loop

int count = 1;

do {
   // body of loop
} 
while(count == 1);

In the above programs, the condition is always true. Hence, the loop body will run for infinite times.

for vs while loops

A for loop is usually used when the number of iterations is known. For example,

// This loop is iterated 5 times
for (int i = 1; i <=5; ++i) {
   // body of the loop
}

Here, we know that the for-loop will be executed 5 times.

However, while and do...while loops are usually used when the number of iterations is unknown. For example,

while (condition) {
    // body of the loop
}

Check out these examples to learn more:

• C++ Program to Display Fibonacci Series
• C++ Program to Find GCD
• C++ Program to Find LCM

C++ break Statement

In this tutorial, we will learn about the break statement and its working in loops with the help of examples.

In C++, the break statement terminates the loop when it is encountered.

The syntax of the break statement is:

break;

Before you learn about the break statement, make sure you know about:

• C++ for loop
• C++ if...else
• C++ while loop

Working of C++ break Statement

Working of break statement in C++

Example 1: break with for loop

// program to print the value of i

#include <iostream>
using namespace std;

int main() {
    for (int i = 1; i <= 5; i++) {
        // break condition     
        if (i == 3) {
            break;
        }
        cout << i << endl;
    }

return 0;
}

Run Code

Output

1
2

In the above program, the for loop is used to print the value of i in each iteration. Here, notice the code:

if (i == 3) {
    break;
}

This means, when i is equal to 3, the break statement terminates the loop. Hence, the output doesn't include values greater than or equal to 3.

Note: The break statement is usually used with decision-making statements.

Example 2: break with while loop

// program to find the sum of positive numbers
// if the user enters a negative numbers, break ends the loop
// the negative number entered is not added to sum

#include <iostream>
using namespace std;

int main() {
    int number;
    int sum = 0;

    while (true) {
        // take input from the user
        cout << "Enter a number: ";
        cin >> number;

        // break condition
        if (number < 0) {
            break;
        }

        // add all positive numbers
        sum += number;
    }

    // display the sum
    cout << "The sum is " << sum << endl;

    return 0;
}

Run Code

Output

Enter a number: 1
Enter a number: 2
Enter a number: 3
Enter a number: -5
The sum is 6. 

In the above program, the user enters a number. The while loop is used to print the total sum of numbers entered by the user. Here, notice the code,

if(number < 0) {
    break;
}

This means, when the user enters a negative number, the break statement terminates the loop and codes outside the loop are executed.

The while loop continues until the user enters a negative number.

break with Nested loop

When break is used with nested loops, break terminates the inner loop. For example,

// using break statement inside
// nested for loop

#include <iostream>
using namespace std;

int main() {
    int number;
    int sum = 0;

    // nested for loops

    // first loop
    for (int i = 1; i <= 3; i++) {
        // second loop
        for (int j = 1; j <= 3; j++) {
            if (i == 2) {
                break;
            }
            cout << "i = " << i << ", j = " << j << endl;
        }
    }

    return 0;
}

Run Code

Output

i = 1, j = 1
i = 1, j = 2
i = 1, j = 3
i = 3, j = 1
i = 3, j = 2
i = 3, j = 3

In the above program, the break statement is executed when i == 2. It terminates the inner loop, and the control flow of the program moves to the outer loop.

Hence, the value of i = 2 is never displayed in the output.

The break statement is also used with the switch statement. To learn more, visit C++ switch statement.

C++ continue Statement

In this tutorial, we will learn about the continue statement and its working with loops with the help of examples.

In computer programming, the continue statement is used to skip the current iteration of the loop and the control of the program goes to the next iteration.

The syntax of the continue statement is:

continue;

Before you learn about the continue statement, make sure you know about,

• C++ for loop
• C++ if...else
• C++ while loop

Working of C++ continue Statement

Working of continue statement in C++

Example 1: continue with for loop

In a for loop, continue skips the current iteration and the control flow jumps to the update expression.

// program to print the value of i

#include <iostream>
using namespace std;

int main() {
    for (int i = 1; i <= 5; i++) {
        // condition to continue
        if (i == 3) {
            continue;
        }

        cout << i << endl;
    }

    return 0;
}

Run Code

Output

1
2
4
5

In the above program, we have used the the for loop to print the value of i in each iteration. Here, notice the code,

if (i == 3) {
    continue;
}

This means

• When i is equal to 3, the continue statement skips the current iteration and starts the next iteration
• Then, i becomes 4, and the condition is evaluated again.
• Hence, 4 and 5 are printed in the next two iterations.

Note: The continue statement is almost always used with decision-making statements.

Example 2: continue with while loop

In a while loop, continue skips the current iteration and control flow of the program jumps back to the while condition.

// program to calculate positive numbers till 50 only
// if the user enters a negative number,
// that number is skipped from the calculation

// negative number -> loop terminate
// numbers above 50 -> skip iteration

#include <iostream>
using namespace std;

int main() {
    int sum = 0;
    int number = 0;

    while (number >= 0) {
        // add all positive numbers
        sum += number;

        // take input from the user
        cout << "Enter a number: ";
        cin >> number;

        // continue condition
        if (number > 50) {
            cout << "The number is greater than 50 and won't be calculated." << endl;
            number = 0;  // the value of number is made 0 again
            continue;
        }
    }

    // display the sum
    cout << "The sum is " << sum << endl;

    return 0;
}

Run Code

Output

Enter a number: 12
Enter a number: 0
Enter a number: 2
Enter a number: 30
Enter a number: 50
Enter a number: 56
The number is greater than 50 and won't be calculated.
Enter a number: 5
Enter a number: -3
The sum is 99 

In the above program, the user enters a number. The while loop is used to print the total sum of positive numbers entered by the user, as long as the numbers entered are not greater than 50.

Notice the use of the continue statement.

 if (number > 50){
    continue;
}

• When the user enters a number greater than 50, the continue statement skips the current iteration. Then the control flow of the program goes to the condition of while loop.
• When the user enters a number less than 0, the loop terminates.

Note: The continue statement works in the same way for the do...while loops.

continue with Nested loop

When continue is used with nested loops, it skips the current iteration of the inner loop. For example,

// using continue statement inside
// nested for loop

#include <iostream>
using namespace std;

int main() {
    int number;
    int sum = 0;

    // nested for loops

    // first loop
    for (int i = 1; i <= 3; i++) {
        // second loop
        for (int j = 1; j <= 3; j++) {
            if (j == 2) {
                continue;
            }
            cout << "i = " << i << ", j = " << j << endl;
        }
    }

    return 0;
}

Run Code

Output

i = 1, j = 1
i = 1, j = 3
i = 2, j = 1
i = 2, j = 3
i = 3, j = 1
i = 3, j = 3

In the above program, when the continue statement executes, it skips the current iteration in the inner loop. And the control of the program moves to the update expression of the inner loop.

Hence, the value of j = 2 is never displayed in the output.

Note: The break statement terminates the loop entirely. However, the continue statement only skips the current iteration.

C++ switch..case Statement

In this tutorial, we will learn about switch statement and its working in C++ programming with the help of some examples.

The switch statement allows us to execute a block of code among many alternatives.

The syntax of the switch statement in C++ is:

switch (expression)  {
    case constant1:
        // code to be executed if 
        // expression is equal to constant1;
        break;

    case constant2:
        // code to be executed if
        // expression is equal to constant2;
        break;
        .
        .
        .
    default:
        // code to be executed if
        // expression doesn't match any constant
}

How does the switch statement work?

The expression is evaluated once and compared with the values of each case label.

• If there is a match, the corresponding code after the matching label is executed. For example, if the value of the variable is equal to constant2, the code after case constant2: is executed until the break statement is encountered.
• If there is no match, the code after default: is executed.

Note: We can do the same thing with the if...else..if ladder. However, the syntax of the switch statement is cleaner and much easier to read and write.

Flowchart of switch Statement

Flowchart of C++ switch...case statement

Example: Create a Calculator using the switch Statement

// Program to build a simple calculator using switch Statement
#include <iostream>
using namespace std;

int main() {
    char oper;
    float num1, num2;
    cout << "Enter an operator (+, -, *, /): ";
    cin >> oper;
    cout << "Enter two numbers: " << endl;
    cin >> num1 >> num2;

    switch (oper) {
        case '+':
            cout << num1 << " + " << num2 << " = " << num1 + num2;
            break;
        case '-':
            cout << num1 << " - " << num2 << " = " << num1 - num2;
            break;
        case '*':
            cout << num1 << " * " << num2 << " = " << num1 * num2;
            break;
        case '/':
            cout << num1 << " / " << num2 << " = " << num1 / num2;
            break;
        default:
            // operator is doesn't match any case constant (+, -, *, /)
            cout << "Error! The operator is not correct";
            break;
    }

    return 0;
}

Run Code

Output 1

Enter an operator (+, -, *, /): +
Enter two numbers: 
2.3
4.5
2.3 + 4.5 = 6.8

Output 2

Enter an operator (+, -, *, /): -
Enter two numbers: 
2.3
4.5
2.3 - 4.5 = -2.2

Output 3

Enter an operator (+, -, *, /): *
Enter two numbers: 
2.3
4.5
2.3 * 4.5 = 10.35

Output 4

Enter an operator (+, -, *, /): /
Enter two numbers: 
2.3
4.5
2.3 / 4.5 = 0.511111

Output 5

Enter an operator (+, -, *, /): ?
Enter two numbers: 
2.3
4.5
Error! The operator is not correct.

In the above program, we are using the switch...case statement to perform addition, subtraction, multiplication, and division.

How This Program Works

1. We first prompt the user to enter the desired operator. This input is then stored in the char variable named oper.
2. We then prompt the user to enter two numbers, which are stored in the float variables num1 and num2.
3. The switch statement is then used to check the operator entered by the user:
   • If the user enters +, addition is performed on the numbers.
   • If the user enters -, subtraction is performed on the numbers.
   • If the user enters *, multiplication is performed on the numbers.
   • If the user enters /, division is performed on the numbers.
   • If the user enters any other character, the default code is printed.

Notice that the break statement is used inside each case block. This terminates the switch statement.

If the break statement is not used, all cases after the correct case are executed.

C++ goto Statement

In this article, you'll learn about goto statment, how it works and why should it be avoided.

In C++ programming, the goto statement is used for altering the normal sequence of program execution by transferring control to some other part of the program.

Syntax of goto Statement

goto label;
... .. ...
... .. ...
... .. ...
label: 
statement;
... .. ...

In the syntax above, label is an identifier. When goto label; is encountered, the control of program jumps to label: and executes the code below it.

Working of goto in C++

Example: goto Statement

// This program calculates the average of numbers entered by the user.
// If the user enters a negative number, it ignores the number and 
// calculates the average number entered before it.

# include <iostream>
using namespace std;

int main()
{
    float num, average, sum = 0.0;
    int i, n;

    cout << "Maximum number of inputs: ";
    cin >> n;

    for(i = 1; i <= n; ++i)
    {
        cout << "Enter n" << i << ": ";
        cin >> num;

        if(num < 0.0)
        {
           // Control of the program move to jump:
            goto jump;
        } 
        sum += num;
    }

jump:
    average = sum / (i - 1);
    cout << "\nAverage = " << average;
    return 0;
}

Output

Maximum number of inputs: 10
Enter n1: 2.3
Enter n2: 5.6
Enter n3: -5.6
Average = 3.95

You can write any C++ program without the use of goto statement and is generally considered a good idea not to use them.

Reason to Avoid goto Statement

The goto statement gives the power to jump to any part of a program but, makes the logic of the program complex and tangled.

In modern programming, the goto statement is considered a harmful construct and a bad programming practice.

The goto statement can be replaced in most of C++ program with the use of break and continue statements.

C++ Functions

C++ Functions

In this tutorial, we will learn about the C++ function and function expressions with the help of examples.

A function is a block of code that performs a specific task.

Suppose we need to create a program to create a circle and color it. We can create two functions to solve this problem:

• a function to draw the circle
• a function to color the circle

Dividing a complex problem into smaller chunks makes our program easy to understand and reusable.

There are two types of function:

1. Standard Library Functions: Predefined in C++
2. User-defined Function: Created by users

In this tutorial, we will focus mostly on user-defined functions.

C++ User-defined Function

C++ allows the programmer to define their own function.

A user-defined function groups code to perform a specific task and that group of code is given a name (identifier).

When the function is invoked from any part of the program, it all executes the codes defined in the body of the function.

C++ Function Declaration

The syntax to declare a function is:

returnType functionName (parameter1, parameter2,...) {
    // function body   
}

Here's an example of a function declaration.

// function declaration
void greet() {
    cout << "Hello World";
}

Here,

• the name of the function is greet()
• the return type of the function is void
• the empty parentheses mean it doesn't have any parameters
• the function body is written inside {}

Note: We will learn about returnType and parameters later in this tutorial.

Calling a Function

In the above program, we have declared a function named greet(). To use the greet() function, we need to call it.

Here's how we can call the above greet() function.

int main() {

    // calling a function   
    greet(); 

}

How Function works in C++

Example 1: Display a Text

#include <iostream>
using namespace std;

// declaring a function
void greet() {
    cout << "Hello there!";
}

int main() {

    // calling the function
    greet();

    return 0;
}

Run Code

Output

Hello there!

Function Parameters

As mentioned above, a function can be declared with parameters (arguments). A parameter is a value that is passed when declaring a function.

For example, let us consider the function below:

void printNum(int num) {
    cout << num;
}

Here, the int variable num is the function parameter.

We pass a value to the function parameter while calling the function.

int main() {
    int n = 7;

    // calling the function
    // n is passed to the function as argument
    printNum(n);

    return 0;
}

Example 2: Function with Parameters

// program to print a text

#include <iostream>
using namespace std;

// display a number
void displayNum(int n1, float n2) {
    cout << "The int number is " << n1;
    cout << "The double number is " << n2;
}

int main() {

     int num1 = 5;
     double num2 = 5.5;

    // calling the function
    displayNum(num1, num2);

    return 0;
}

Run Code

Output

The int number is 5
The double number is 5.5

In the above program, we have used a function that has one int parameter and one double parameter.

We then pass num1 and num2 as arguments. These values are stored by the function parameters n1 and n2 respectively.

C++ function with parameters

Note: The type of the arguments passed while calling the function must match with the corresponding parameters defined in the function declaration.

Return Statement

In the above programs, we have used void in the function declaration. For example,

void displayNumber() {
    // code
}

This means the function is not returning any value.

It's also possible to return a value from a function. For this, we need to specify the returnType of the function during function declaration.

Then, the return statement can be used to return a value from a function.

For example,

int add (int a, int b) {
   return (a + b);
}

Here, we have the data type int instead of void. This means that the function returns an int value.

The code return (a + b); returns the sum of the two parameters as the function value.

The return statement denotes that the function has ended. Any code after return inside the function is not executed.

Example 3: Add Two Numbers

// program to add two numbers using a function

#include <iostream>

using namespace std;

// declaring a function
int add(int a, int b) {
    return (a + b);
}

int main() {

    int sum;

    // calling the function and storing
    // the returned value in sum
    sum = add(100, 78);

    cout << "100 + 78 = " << sum << endl;

    return 0;
}

Run Code

Output

100 + 78 = 178

In the above program, the add() function is used to find the sum of two numbers.

We pass two int literals 100 and 78 while calling the function.

We store the returned value of the function in the variable sum, and then we print it.

Working of C++ Function with return statement

Notice that sum is a variable of int type. This is because the return value of add() is of int type.

Function Prototype

In C++, the code of function declaration should be before the function call. However, if we want to define a function after the function call, we need to use the function prototype. For example,

// function prototype
void add(int, int);

int main() {
    // calling the function before declaration.
    add(5, 3);
    return 0;
}

// function definition
void add(int a, int b) {
    cout << (a + b);
}

In the above code, the function prototype is:

void add(int, int);

This provides the compiler with information about the function name and its parameters. That's why we can use the code to call a function before the function has been defined.

The syntax of a function prototype is:

returnType functionName(dataType1, dataType2, ...);

Example 4: C++ Function Prototype

// using function definition after main() function
// function prototype is declared before main()

#include <iostream>

using namespace std;

// function prototype
int add(int, int);

int main() {
    int sum;

    // calling the function and storing
    // the returned value in sum
    sum = add(100, 78);

    cout << "100 + 78 = " << sum << endl;

    return 0;
}

// function definition
int add(int a, int b) {
    return (a + b);
}

Run Code

Output

100 + 78 = 178

The above program is nearly identical to Example 3. The only difference is that here, the function is defined after the function call.

That's why we have used a function prototype in this example.

Benefits of Using User-Defined Functions

• Functions make the code reusable. We can declare them once and use them multiple times.
• Functions make the program easier as each small task is divided into a function.
• Functions increase readability.

C++ Library Functions

Library functions are the built-in functions in C++ programming.

Programmers can use library functions by invoking the functions directly; they don't need to write the functions themselves.

Some common library functions in C++ are sqrt(), abs(), isdigit(), etc.

In order to use library functions, we usually need to include the header file in which these library functions are defined.

For instance, in order to use mathematical functions such as sqrt() and abs(), we need to include the header file cmath.

Example 5: C++ Program to Find the Square Root of a Number

#include <iostream>
#include <cmath>
using namespace std;

int main() {
    double number, squareRoot;

    number = 25.0;

    // sqrt() is a library function to calculate the square root
    squareRoot = sqrt(number);

    cout << "Square root of " << number << " = " << squareRoot;

    return 0;
}

Run Code

Output

Square root of 25 = 5

In this program, the sqrt() library function is used to calculate the square root of a number.

The function declaration of sqrt() is defined in the cmath header file. That's why we need to use the code #include <cmath> to use the sqrt() function.

To learn more, visit C++ Standard Library functions.

C++ User-defined Function Types

In this tutorial, you will learn about different approaches you can take to solve a single problem using functions.

For better understanding of arguments and return in functions, user-defined functions can be categorised as:

• Function with no argument and no return value
• Function with no argument but return value
• Function with argument but no return value
• Function with argument and return value

Consider a situation in which you have to check prime number. This problem is solved below by making user-defined function in 4 different ways as mentioned above.

Example 1: No arguments passed and no return value

# include <iostream>
using namespace std;

void prime();

int main()
{
    // No argument is passed to prime()
    prime();
    return 0;
}


// Return type of function is void because value is not returned.
void prime()
{

    int num, i, flag = 0;

    cout << "Enter a positive integer enter to check: ";
    cin >> num;

    for(i = 2; i <= num/2; ++i)
    {
        if(num % i == 0)
        {
            flag = 1; 
            break;
        }
    }

    if (flag == 1)
    {
        cout << num << " is not a prime number.";
    }
    else
    {
        cout << num << " is a prime number.";
    }
}

In the above program, prime() is called from the main() with no arguments.

prime() takes the positive number from the user and checks whether the number is a prime number or not.

Since, return type of prime() is void, no value is returned from the function.

Example 2: No arguments passed but a return value

#include <iostream>
using namespace std;

int prime();

int main()
{
    int num, i, flag = 0;

    // No argument is passed to prime()
    num = prime();
    for (i = 2; i <= num/2; ++i)
    {
        if (num%i == 0)
        {
            flag = 1;
            break;
        }
    }

    if (flag == 1)
    {
        cout<<num<<" is not a prime number.";
    }
    else
    {
        cout<<num<<" is a prime number.";
    }
    return 0;
}

// Return type of function is int
int prime()
{
    int n;

    printf("Enter a positive integer to check: ");
    cin >> n;

    return n;
}

In the above program, prime() function is called from the main() with no arguments.

prime() takes a positive integer from the user. Since, return type of the function is an int, it returns the inputted number from the user back to the calling main() function.

Then, whether the number is prime or not is checked in the main() itself and printed onto the screen.

Example 3: Arguments passed but no return value

#include <iostream>
using namespace std;

void prime(int n);

int main()
{
    int num;
    cout << "Enter a positive integer to check: ";
    cin >> num;

    // Argument num is passed to the function prime()
    prime(num);
    return 0;
}

// There is no return value to calling function. Hence, return type of function is void. */
void prime(int n)
{
    int i, flag = 0;
    for (i = 2; i <= n/2; ++i)
    {
        if (n%i == 0)
        {
            flag = 1;
            break;
        }
    }

    if (flag == 1)
    {
        cout << n << " is not a prime number.";
    }
    else {
        cout << n << " is a prime number.";
    }
}

In the above program, positive number is first asked from the user which is stored in the variable num.

Then, num is passed to the prime() function where, whether the number is prime or not is checked and printed.

Since, the return type of prime() is a void, no value is returned from the function.

Example 4: Arguments passed and a return value.

#include <iostream>
using namespace std;

int prime(int n);

int main()
{
    int num, flag = 0;
    cout << "Enter positive integer to check: ";
    cin >> num;

    // Argument num is passed to check() function
    flag = prime(num);

    if(flag == 1)
        cout << num << " is not a prime number.";
    else
        cout<< num << " is a prime number.";
    return 0;
}

/* This function returns integer value.  */
int prime(int n)
{
    int i;
    for(i = 2; i <= n/2; ++i)
    {
        if(n % i == 0)
            return 1;
    }

    return 0;
}

In the above program, a positive integer is asked from the user and stored in the variable num.

Then, num is passed to the function prime() where, whether the number is prime or not is checked.

Since, the return type of prime() is an int, 1 or 0 is returned to the main() calling function. If the number is a prime number, 1 is returned. If not, 0 is returned.

Back in the main() function, the returned 1 or 0 is stored in the variable flag, and the corresponding text is printed onto the screen.

Which method is better?

All four programs above gives the same output and all are technically correct program.

There is no hard and fast rule on which method should be chosen.

The particular method is chosen depending upon the situation and how you want to solve a problem.

C++ Function Overloading

In this tutorial, we will learn about the function overloading in C++ with examples.

In C++, two functions can have the same name if the number and/or type of arguments passed is different.

These functions having the same name but different arguments are known as overloaded functions. For example:

// same name different arguments
int test() { }
int test(int a) { }
float test(double a) { }
int test(int a, double b) { }

Here, all 4 functions are overloaded functions.

Notice that the return types of all these 4 functions are not the same. Overloaded functions may or may not have different return types but they must have different arguments. For example,

// Error code
int test(int a) { }
double test(int b){ }

Here, both functions have the same name, the same type, and the same number of arguments. Hence, the compiler will throw an error.

Example 1: Overloading Using Different Types of Parameter

// Program to compute absolute value
// Works for both int and float

#include <iostream>
using namespace std;

// function with float type parameter
float absolute(float var){
    if (var < 0.0)
        var = -var;
    return var;
}

// function with int type parameter
int absolute(int var) {
     if (var < 0)
         var = -var;
    return var;
}

int main() {

    // call function with int type parameter
    cout << "Absolute value of -5 = " << absolute(-5) << endl;

    // call function with float type parameter
    cout << "Absolute value of 5.5 = " << absolute(5.5f) << endl;
    return 0;
}

Run Code

Output

Absolute value of -5 = 5
Absolute value of 5.5 = 5.5

Working of overloading for the absolute() function

In this program, we overload the absolute() function. Based on the type of parameter passed during the function call, the corresponding function is called.

Example 2: Overloading Using Different Number of Parameters

#include <iostream>
using namespace std;

// function with 2 parameters
void display(int var1, double var2) {
    cout << "Integer number: " << var1;
    cout << " and double number: " << var2 << endl;
}

// function with double type single parameter
void display(double var) {
    cout << "Double number: " << var << endl;
}

// function with int type single parameter
void display(int var) {
    cout << "Integer number: " << var << endl;
}

int main() {

    int a = 5;
    double b = 5.5;

    // call function with int type parameter
    display(a);

    // call function with double type parameter
    display(b);

    // call function with 2 parameters
    display(a, b);

    return 0;
}

Run Code

Output

Integer number: 5
Float number: 5.5
Integer number: 5 and double number: 5.5

Here, the display() function is called three times with different arguments. Depending on the number and type of arguments passed, the corresponding display() function is called.

Working of overloading for the display() function

The return type of all these functions is the same but that need not be the case for function overloading.

Note: In C++, many standard library functions are overloaded. For example, the sqrt() function can take double, float, int, etc. as parameters. This is possible because the sqrt() function is overloaded in C++.

C++ Programming Default Arguments (Parameters)

In this tutorial, we will learn C++ default arguments and their working with the help of examples.

In C++ programming, we can provide default values for function parameters.

If a function with default arguments is called without passing arguments, then the default parameters are used.

However, if arguments are passed while calling the function, the default arguments are ignored.

Working of default arguments

How default arguments work in C++

We can understand the working of default arguments from the image above:

1. When temp() is called, both the default parameters are used by the function.

2. When temp(6) is called, the first argument becomes 6 while the default value is used for the second parameter.

3. When temp(6, -2.3) is called, both the default parameters are overridden, resulting in i = 6 and f = -2.3.

4. When temp(3.4) is passed, the function behaves in an undesired way because the second argument cannot be passed without passing the first argument.

   Therefore, 3.4 is passed as the first argument. Since the first argument has been defined as int, the value that is actually passed is 3.

Example: Default Argument

#include <iostream>
using namespace std;

// defining the default arguments
void display(char = '*', int = 3);

int main() {
    int count = 5;

    cout << "No argument passed: ";
    // *, 3 will be parameters
    display(); 

    cout << "First argument passed: ";
     // #, 3 will be parameters
    display('#'); 

    cout << "Both arguments passed: ";
    // $, 5 will be parameters
    display('$', count); 

    return 0;
}

void display(char c, int count) {
    for(int i = 1; i <= count; ++i)
    {
        cout << c;
    }
    cout << endl;
}

Run Code

Output

No argument passed: ***
First argument passed: ###
Both arguments passed: $$$$$

Here is how this program works:

1. display() is called without passing any arguments. In this case, display() uses both the default parameters c = '*' and n = 1.
2. display('#') is called with only one argument. In this case, the first becomes '#'. The second default parameter n = 1 is retained.
3. display('#', count) is called with both arguments. In this case, default arguments are not used.

We can also define the default parameters in the function definition itself. The program below is equivalent to the one above.

#include <iostream>
using namespace std;

// defining the default arguments
void display(char c = '*', int count = 3) {
    for(int i = 1; i <= count; ++i) {
        cout << c;
    }
    cout << endl;
}

int main() {
    int count = 5;

    cout << "No argument passed: ";
    // *, 3 will be parameters
    display(); 

    cout << "First argument passed: ";
     // #, 3 will be parameters
    display('#'); 

    cout << "Both argument passed: ";
    // $, 5 will be parameters
    display('$', count); 

    return 0;
}

Run Code

Things to Remember

1. Once we provide a default value for a parameter, all subsequent parameters must also have default values. For example,

   // Invalid
   void add(int a, int b = 3, int c, int d);
   
   // Invalid
   void add(int a, int b = 3, int c, int d = 4);
   
   // Valid
   void add(int a, int c, int b = 3, int d = 4);
   

2. If we are defining the default arguments in the function definition instead of the function prototype, then the function must be defined before the function call.

   // Invalid code
   
   int main() {
      // function call
      display();
   }
   
   void display(char c = '*', int count = 5) {
      // code
   }
   

C++ Storage Class

In this article, you'll learn about different storage classes in C++. Namely: local, global, static local, register and thread local.

Every variable in C++ has two features: type and storage class.

Type specifies the type of data that can be stored in a variable. For example: int, float, char etc.

And, storage class controls two different properties of a variable: lifetime (determines how long a variable can exist) and scope (determines which part of the program can access it).

Depending upon the storage class of a variable, it can be divided into 4 major types:

• Local variable
• Global variable
• Static local variable
• Register Variable
• Thread Local Storage

Local Variable

A variable defined inside a function (defined inside function body between braces) is called a local variable or automatic variable.

Its scope is only limited to the function where it is defined. In simple terms, local variable exists and can be accessed only inside a function.

The life of a local variable ends (It is destroyed) when the function exits.

Example 1: Local variable

#include <iostream>
using namespace std;

void test();

int main() 
{
    // local variable to main()
    int var = 5;

    test();

    // illegal: var1 not declared inside main()
    var1 = 9;
}

void test()
{
    // local variable to test()
    int var1;
    var1 = 6;

    // illegal: var not declared inside test()
    cout << var;
}

The variable var cannot be used inside test() and var1 cannot be used inside main() function.

Keyword auto was also used for defining local variables before as: auto int var;

But, after C++11 auto has a different meaning and should not be used for defining local variables.

Global Variable

If a variable is defined outside all functions, then it is called a global variable.

The scope of a global variable is the whole program. This means, It can be used and changed at any part of the program after its declaration.

Likewise, its life ends only when the program ends.

Example 2: Global variable

#include <iostream>
using namespace std;

// Global variable declaration
int c = 12;

void test();

int main()
{
    ++c;

    // Outputs 13
    cout << c <<endl;
    test();

    return 0;
}

void test()
{
    ++c;

    // Outputs 14
    cout << c;
}

Output

13
14

In the above program, c is a global variable.

This variable is visible to both functions main() and test() in the above program.

Static Local variable

Keyword static is used for specifying a static variable. For example:

... .. ...
int main()
{
   static float a;
   ... .. ...
}

A static local variable exists only inside a function where it is declared (similar to a local variable) but its lifetime starts when the function is called and ends only when the program ends.

The main difference between local variable and static variable is that, the value of static variable persists the end of the program.

Example 3: Static local variable

#include <iostream>
using namespace std;

void test()
{
    // var is a static variable
    static int var = 0;
    ++var;

    cout << var << endl;
}

int main()
{

    test();
    test();

    return 0;
}

Output

1
2

In the above program, test() function is invoked 2 times.

During the first call, variable var is declared as static variable and initialized to 0. Then 1 is added to var which is displayed in the screen.

When the function test() returns, variable var still exists because it is a static variable.

During second function call, no new variable var is created. The same var is increased by 1 and then displayed to the screen.

Output of above program if var was not specified as static variable

1
1

Register Variable (Deprecated in C++11)

Keyword register is used for specifying register variables.

Register variables are similar to automatic variables and exists inside a particular function only. It is supposed to be faster than the local variables.

If a program encounters a register variable, it stores the variable in processor's register rather than memory if available. This makes it faster than the local variables.

However, this keyword was deprecated in C++11 and should not be used.

Thread Local Storage

Thread-local storage is a mechanism by which variables are allocated such that there is one instance of the variable per extant thread.

Keyword thread_local is used for this purpose.

Learn more about thread local storage.

C++ Recursion

In this tutorial, we will learn about recursive function in C++ and its working with the help of examples.

A function that calls itself is known as a recursive function. And, this technique is known as recursion.

Working of Recursion in C++

void recurse()
{
    ... .. ...
    recurse();
    ... .. ...
}

int main()
{
    ... .. ...
    recurse();
    ... .. ...
}

The figure below shows how recursion works by calling itself over and over again.

How recursion works in C++ programming

The recursion continues until some condition is met.

To prevent infinite recursion, if...else statement (or similar approach) can be used where one branch makes the recursive call and the other doesn't.

Example 1: Factorial of a Number Using Recursion

// Factorial of n = 1*2*3*...*n

#include <iostream>
using namespace std;

int factorial(int);

int main() {
    int n, result;

    cout << "Enter a non-negative number: ";
    cin >> n;

    result = factorial(n);
    cout << "Factorial of " << n << " = " << result;
    return 0;
}

int factorial(int n) {
    if (n > 1) {
        return n * factorial(n - 1);
    } else {
        return 1;
    }
}

Run Code

Output

Enter a non-negative number: 4
Factorial of 4 = 24

Working of Factorial Program

How this C++ recursion program works

As we can see, the factorial() function is calling itself. However, during each call, we have decreased the value of n by 1. When n is less than 1, the factorial() function ultimately returns the output.

Advantages and Disadvantages of Recursion

Below are the pros and cons of using recursion in C++.

Advantages of C++ Recursion

• It makes our code shorter and cleaner.
• Recursion is required in problems concerning data structures and advanced algorithms, such as Graph and Tree Traversal.

Disadvantages of C++ Recursion

• It takes a lot of stack space compared to an iterative program.
• It uses more processor time.
• It can be more difficult to debug compared to an equivalent iterative program.

C++ Return by Reference

In this article, you'll learn how to return a value by reference in a function and use it efficiently in your program.

In C++ Programming, not only can you pass values by reference to a function but you can also return a value by reference.

To understand this feature, you should have the knowledge of:

• Global variables

Example: Return by Reference

#include <iostream>
using namespace std;

// global variable
int num;

// function declaration
int& test();

int main() {

  // assign 5 to num variable
  // equivalent to num = 5;
  test() = 5;

  cout << num;

  return 0;
}

// function definition
// returns the address of num variable
int& test() {
  return num;
}

Output

5

In program above, the return type of function test() is int&. Hence, this function returns a reference of the variable num.

The return statement is return num;. Unlike return by value, this statement doesn't return value of num, instead it returns the variable itself (address).

So, when the variable is returned, it can be assigned a value as done in test() = 5;

This stores 5 to the variable num, which is displayed onto the screen.

Important Things to Remember When Returning by Reference.

• Ordinary function returns value but this function doesn't. Hence, you cannot return a constant from the function.

  int& test() {
  
      return 2;
  
  }
  

• You cannot return a local variable from this function.

  int& test() {
  
      int n = 2; 
      return n; 
  
  }
  

C++ Arrays & String

C++ Arrays

In this tutorial, we will learn to work with arrays. We will learn to declare, initialize, and access array elements in C++ programming with the help of examples.

In C++, an array is a variable that can store multiple values of the same type. For example,

Suppose a class has 27 students, and we need to store the grades of all of them. Instead of creating 27 separate variables, we can simply create an array:

double grade[27];

Here, grade is an array that can hold a maximum of 27 elements of double type.

In C++, the size and type of arrays cannot be changed after its declaration.

C++ Array Declaration

dataType arrayName[arraySize];

For example,

int x[6];

Here,

• int - type of element to be stored
• x - name of the array
• 6 - size of the array

Access Elements in C++ Array

In C++, each element in an array is associated with a number. The number is known as an array index. We can access elements of an array by using those indices.

// syntax to access array elements
array[index];

Consider the array x we have seen above.

Elements of an array in C++

Few Things to Remember:

• The array indices start with 0. Meaning x[0] is the first element stored at index 0.

• If the size of an array is n, the last element is stored at index (n-1). In this example, x[5] is the last element.

• Elements of an array have consecutive addresses. For example, suppose the starting address of x[0] is 2120.

  Then, the address of the next element x[1] will be 2124, the address of x[2] will be 2128, and so on.

  Here, the size of each element is increased by 4. This is because the size of int is 4 bytes.

C++ Array Initialization

In C++, it's possible to initialize an array during declaration. For example,

// declare and initialize and array
int x[6] = {19, 10, 8, 17, 9, 15};

C++ Array elements and their data

Another method to initialize array during declaration:

// declare and initialize an array
int x[] = {19, 10, 8, 17, 9, 15};

Here, we have not mentioned the size of the array. In such cases, the compiler automatically computes the size.

C++ Array With Empty Members

In C++, if an array has a size n, we can store upto n number of elements in the array. However, what will happen if we store less than n number of elements.

For example,

// store only 3 elements in the array
int x[6] = {19, 10, 8};

Here, the array x has a size of 6. However, we have initialized it with only 3 elements.

In such cases, the compiler assigns random values to the remaining places. Oftentimes, this random value is simply 0.

Empty array members are automatically assigned the value 0

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
// store the value at third position
cin >> mark[2];


// take input from the user
// insert at ith position
cin >> mark[i-1];

// print first element of the array
cout << mark[0];

// print ith element of the array
cout >> mark[i-1];

Example 1: Displaying Array Elements

#include <iostream>
using namespace std;

int main() {

  int numbers[5] = {7, 5, 6, 12, 35};

  cout << "The numbers are: ";

  //  Printing array elements
  // using range based for loop
  for (const int &n : numbers) {
    cout << n << "  ";
  }

  cout << "\nThe numbers are: ";

  //  Printing array elements
  // using traditional for loop
  for (int i = 0; i < 5; ++i) {
    cout << numbers[i] << "  ";
  }

  return 0;
}

Run Code

Output

The numbers are: 7  5  6  12  35
The numbers are: 7  5  6  12  35

Here, we have used a for loop to iterate from i = 0 to i = 4. In each iteration, we have printed numbers[i].

We again used a range-based for loop to print out the elements of the array. To learn more about this loop, check C++ Ranged for Loop.

Note: In our range-based loop, we have used the code const int &n instead of int n as the range declaration. However, the const int &n is more preferred because:

1. Using int n simply copies the array elements to the variable n during each iteration. This is not memory-efficient.

   &n, however, uses the memory address of the array elements to access their data without copying them to a new variable. This is memory-efficient.

2. We are simply printing the array elements, not modifying them. Therefore, we use const so as not to accidentally change the values of the array.

Example 2: Take Inputs from User and Store Them in an Array

#include <iostream>
using namespace std;

int main() {

  int numbers[5];

  cout << "Enter 5 numbers: " << endl;

  //  store input from user to array
  for (int i = 0; i < 5; ++i) {
    cin >> numbers[i];
  }

  cout << "The numbers are: ";

  //  print array elements
  for (int n = 0; n < 5; ++n) {
    cout << numbers[n] << "  ";
  }

  return 0;
}

Run Code

Output

Enter 5 numbers: 
11
12
13
14
15
The numbers are: 11  12  13  14  15

Once again, we have used a for loop to iterate from i = 0 to i = 4. In each iteration, we took an input from the user and stored it in numbers[i].

Then, we used another for loop to print all the array elements.

Example 3: Display Sum and Average of Array Elements Using for Loop

#include <iostream>
using namespace std;

int main() {

  // initialize an array without specifying size
  double numbers[] = {7, 5, 6, 12, 35, 27};

  double sum = 0;
  double count = 0;
  double average;

  cout << "The numbers are: ";

  //  print array elements
  // use of range-based for loop
  for (const double &n : numbers) {
    cout << n << "  ";

    //  calculate the sum
    sum += n;

    // count the no. of array elements
    ++count;
  }

  // print the sum
  cout << "\nTheir Sum = " << sum << endl;

  // find the average
  average = sum / count;
  cout << "Their Average = " << average << endl;

  return 0;
}

Run Code

Output

The numbers are: 7  5  6  12  35  27
Their Sum = 92
Their Average = 15.3333

In this program:

1. We have initialized a double array named numbers but without specifying its size. We also declared three double variables sum, count, and average.

   Here, sum =0 and count = 0.

2. Then we used a range-based for loop to print the array elements. In each iteration of the loop, we add the current array element to sum.

3. We also increase the value of count by 1 in each iteration, so that we can get the size of the array by the end of the for loop.

4. After printing all the elements, we print the sum and the average of all the numbers. The average of the numbers is given by average = sum / count;

Note: We used a ranged for loop instead of a normal for loop.

A normal for loop requires us to specify the number of iterations, which is given by the size of the array.

But a ranged for loop does not require such specifications.

C++ Array Out of Bounds

If we declare an array of size 10, then the array will contain elements from index 0 to 9.

However, if we try to access the element at index 10 or more than 10, it will result in Undefined Behaviour.

C++ Multidimensional Arrays

In this tutorial, we'll learn about multi-dimensional arrays in C++. More specifically, how to declare them, access them, and use them efficiently in our program.

In C++, we can create an array of an array, known as a multidimensional array. For example:

int x[3][4];

Here, x is a two-dimensional array. It can hold a maximum of 12 elements.

We can think of this array as a table with 3 rows and each row has 4 columns as shown below.

Elements in two-dimensional array in C++ Programming

Three-dimensional arrays also work in a similar way. For example:

float x[2][4][3];

This array x can hold a maximum of 24 elements.

We can find out the total number of elements in the array simply by multiplying its dimensions:

2 x 4 x 3 = 24

Multidimensional Array Initialization

Like a normal array, we can initialize a multidimensional array in more than one way.

1. Initialization of two-dimensional array

int test[2][3] = {2, 4, 5, 9, 0, 19};

The above method is not preferred. A better way to initialize this array with the same array elements is given below:

int  test[2][3] = { {2, 4, 5}, {9, 0, 19}};

This array has 2 rows and 3 columns, which is why we have two rows of elements with 3 elements each.

Initializing a two-dimensional array in C++

2. Initialization of three-dimensional array

int test[2][3][4] = {3, 4, 2, 3, 0, -3, 9, 11, 23, 12, 23, 
                 2, 13, 4, 56, 3, 5, 9, 3, 5, 5, 1, 4, 9};

This is not a good way of initializing a three-dimensional array. A better way to initialize this array is:

int test[2][3][4] = { 
                     { {3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23, 2} },
                     { {13, 4, 56, 3}, {5, 9, 3, 5}, {5, 1, 4, 9} }
                 };

Notice the dimensions of this three-dimensional array.

The first dimension has the value 2. So, the two elements comprising the first dimension are:

Element 1 = { {3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23, 2} }
Element 2 = { {13, 4, 56, 3}, {5, 9, 3, 5}, {5, 1, 4, 9} }

The second dimension has the value 3. Notice that each of the elements of the first dimension has three elements each:

{3, 4, 2, 3}, {0, -3, 9, 11} and {23, 12, 23, 2} for Element 1.
{13, 4, 56, 3}, {5, 9, 3, 5} and {5, 1, 4, 9} for Element 2.

Finally, there are four int numbers inside each of the elements of the second dimension:

{3, 4, 2, 3}
{0, -3, 9, 11}
... .. ...
... .. ...

Example 1: Two Dimensional Array

// C++ Program to display all elements
// of an initialised two dimensional array

#include <iostream>
using namespace std;

int main() {
    int test[3][2] = {{2, -5},
                      {4, 0},
                      {9, 1}};

    // use of nested for loop
    // access rows of the array
    for (int i = 0; i < 3; ++i) {

        // access columns of the array
        for (int j = 0; j < 2; ++j) {
            cout << "test[" << i << "][" << j << "] = " << test[i][j] << endl;
        }
    }

    return 0;
}

Run Code

Output

test[0][0] = 2
test[0][1] = -5
test[1][0] = 4
test[1][1] = 0
test[2][0] = 9
test[2][1] = 1

In the above example, we have initialized a two-dimensional int array named test that has 3 "rows" and 2 "columns".

Here, we have used the nested for loop to display the array elements.

• the outer loop from i == 0 to i == 2 access the rows of the array
• the inner loop from j == 0 to j == 1 access the columns of the array

Finally, we print the array elements in each iteration.

Example 2: Taking Input for Two Dimensional Array

#include <iostream>
using namespace std;

int main() {
    int numbers[2][3];

    cout << "Enter 6 numbers: " << endl;

    // Storing user input in the array
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 3; ++j) {
            cin >> numbers[i][j];
        }
    }

    cout << "The numbers are: " << endl;

    //  Printing array elements
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 3; ++j) {
            cout << "numbers[" << i << "][" << j << "]: " << numbers[i][j] << endl;
        }
    }

    return 0;
}

Run Code

Output

Enter 6 numbers: 
1
2
3
4
5
6
The numbers are:
numbers[0][0]: 1
numbers[0][1]: 2
numbers[0][2]: 3
numbers[1][0]: 4
numbers[1][1]: 5
numbers[1][2]: 6

Here, we have used a nested for loop to take the input of the 2d array. Once all the input has been taken, we have used another nested for loop to print the array members.

Example 3: Three Dimensional Array

// C++ Program to Store value entered by user in
// three dimensional array and display it.

#include <iostream>
using namespace std;

int main() {
    // This array can store upto 12 elements (2x3x2)
    int test[2][3][2] = {
                            {
                                {1, 2},
                                {3, 4},
                                {5, 6}
                            }, 
                            {
                                {7, 8}, 
                                {9, 10}, 
                                {11, 12}
                            }
                        };

    // Displaying the values with proper index.
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 3; ++j) {
            for (int k = 0; k < 2; ++k) {
                cout << "test[" << i << "][" << j << "][" << k << "] = " << test[i][j][k] << endl;
            }
        }
    }

    return 0;
}

Run Code

Output

test[0][0][0] = 1
test[0][0][1] = 2
test[0][1][0] = 3
test[0][1][1] = 4
test[0][2][0] = 5
test[0][2][1] = 6
test[1][0][0] = 7
test[1][0][1] = 8
test[1][1][0] = 9
test[1][1][1] = 10
test[1][2][0] = 11
test[1][2][1] = 12

The basic concept of printing elements of a 3d array is similar to that of a 2d array.

However, since we are manipulating 3 dimensions, we use a nested for loop with 3 total loops instead of just 2:

• the outer loop from i == 0 to i == 1 accesses the first dimension of the array
• the middle loop from j == 0 to j == 2 accesses the second dimension of the array
• the innermost loop from k == 0 to k == 1 accesses the third dimension of the array

As we can see, the complexity of the array increases exponentially with the increase in dimensions.

Passing Array to a Function in C++ Programming

In this tutorial, we will learn how to pass a single-dimensional and multidimensional array as a function parameter in C++ with the help of examples.

In C++, we can pass arrays as an argument to a function. And, also we can return arrays from a function.

Before you learn about passing arrays as a function argument, make sure you know about C++ Arrays and C++ Functions.

Syntax for Passing Arrays as Function Parameters

The syntax for passing an array to a function is:

returnType functionName(dataType arrayName[arraySize]) {
    // code
}

Let's see an example,

int total(int marks[5]) {
    // code
}

Here, we have passed an int type array named marks to the function total(). The size of the array is 5.

Example 1: Passing One-dimensional Array to a Function

// C++ Program to display marks of 5 students

#include <iostream>
using namespace std;

// declare function to display marks
// take a 1d array as parameter
void display(int m[5]) {
    cout << "Displaying marks: " << endl;

    // display array elements    
    for (int i = 0; i < 5; ++i) {
        cout << "Student " << i + 1 << ": " << m[i] << endl;
    }
}

int main() {

    // declare and initialize an array
    int marks[5] = {88, 76, 90, 61, 69};

    // call display function
    // pass array as argument
    display(marks);

    return 0;
}

Run Code

Output

Displaying marks: 
Student 1: 88
Student 2: 76
Student 3: 90
Student 4: 61
Student 5: 69

Here,

1. When we call a function by passing an array as the argument, only the name of the array is used.

   display(marks);
   

   Here, the argument marks represent the memory address of the first element of array marks[5].

2. However, notice the parameter of the display() function.

   void display(int m[5])
   

   Here, we use the full declaration of the array in the function parameter, including the square braces [].

3. The function parameter int m[5] converts to int* m;. This points to the same address pointed by the array marks. This means that when we manipulate m[5] in the function body, we are actually manipulating the original array marks.

   C++ handles passing an array to a function in this way to save memory and time.

Passing Multidimensional Array to a Function

We can also pass Multidimensional arrays as an argument to the function. For example,

Example 2: Passing Multidimensional Array to a Function

// C++ Program to display the elements of two
// dimensional array by passing it to a function

#include <iostream>
using namespace std;

// define a function 
// pass a 2d array as a parameter
void display(int n[][2]) {
    cout << "Displaying Values: " << endl;
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 2; ++j) {
            cout << "num[" << i << "][" << j << "]: " << n[i][j] << endl;
        }
    }
}

int main() {

    // initialize 2d array
    int num[3][2] = {
        {3, 4},
        {9, 5},
        {7, 1}
    };

    // call the function
    // pass a 2d array as an argument
    display(num);

    return 0;
}

Run Code

Output

Displaying Values: 
num[0][0]: 3
num[0][1]: 4
num[1][0]: 9
num[1][1]: 5
num[2][0]: 7
num[2][1]: 1

In the above program, we have defined a function named display(). The function takes a two dimensional array, int n[][2] as its argument and prints the elements of the array.

While calling the function, we only pass the name of the two dimensional array as the function argument display(num).

Note: It is not mandatory to specify the number of rows in the array. However, the number of columns should always be specified. This is why we have used int n[][2].

We can also pass arrays with more than 2 dimensions as a function argument.

C++ Returning an Array From a Function

We can also return an array from the function. However, the actual array is not returned. Instead the address of the first element of the array is returned with the help of pointers.

We will learn about returning arrays from a function in the coming tutorials.

C++ Strings

In this tutorial, you'll learn to handle strings in C++. You'll learn to declare them, initialize them and use them for various input/output operations.

String is a collection of characters. There are two types of strings commonly used in C++ programming language:

• Strings that are objects of string class (The Standard C++ Library string class)
• C-strings (C-style Strings)

C-strings

In C programming, the collection of characters is stored in the form of arrays. This is also supported in C++ programming. Hence it's called C-strings.

C-strings are arrays of type char terminated with null character, that is, \0 (ASCII value of null character is 0).

How to define a C-string?

char str[] = "C++";

In the above code, str is a string and it holds 4 characters.

Although, "C++" has 3 character, the null character \0 is added to the end of the string automatically.

Alternative ways of defining a string

char str[4] = "C++";

char str[] = {'C','+','+','\0'};
char str[4] = {'C','+','+','\0'};

Like arrays, it is not necessary to use all the space allocated for the string. For example:

char str[100] = "C++";

Example 1: C++ String to read a word

C++ program to display a string entered by user.

#include <iostream>
using namespace std;

int main()
{
    char str[100];

    cout << "Enter a string: ";
    cin >> str;
    cout << "You entered: " << str << endl;

    cout << "\nEnter another string: ";
    cin >> str;
    cout << "You entered: "<<str<<endl;

    return 0;
}

Output

Enter a string: C++
You entered: C++
Enter another string: Programming is fun.
You entered: Programming

Notice that, in the second example only "Programming" is displayed instead of "Programming is fun".

This is because the extraction operator >> works as scanf() in C and considers a space " " has a terminating character.

Example 2: C++ String to read a line of text

C++ program to read and display an entire line entered by user.

#include <iostream>
using namespace std;

int main()
{
    char str[100];
    cout << "Enter a string: ";
    cin.get(str, 100);

    cout << "You entered: " << str << endl;
    return 0;
}

Output

Enter a string: Programming is fun.
You entered: Programming is fun.

To read the text containing blank space, cin.get function can be used. This function takes two arguments.

First argument is the name of the string (address of first element of string) and second argument is the maximum size of the array.

In the above program, str is the name of the string and 100 is the maximum size of the array.

string Object

In C++, you can also create a string object for holding strings.

Unlike using char arrays, string objects has no fixed length, and can be extended as per your requirement.

Example 3: C++ string using string data type

#include <iostream>
using namespace std;

int main()
{
    // Declaring a string object
    string str;
    cout << "Enter a string: ";
    getline(cin, str);

    cout << "You entered: " << str << endl;
    return 0;
}

Output

Enter a string: Programming is fun.
You entered: Programming is fun.

In this program, a string str is declared. Then the string is asked from the user.

Instead of using cin>> or cin.get() function, you can get the entered line of text using getline().

getline() function takes the input stream as the first parameter which is cin and str as the location of the line to be stored.

Passing String to a Function

Strings are passed to a function in a similar way arrays are passed to a function.

#include <iostream>

using namespace std;

void display(char *);
void display(string);

int main()
{
    string str1;
    char str[100];

    cout << "Enter a string: ";
    getline(cin, str1);

    cout << "Enter another string: ";
    cin.get(str, 100, '\n');

    display(str1);
    display(str);
    return 0;
}

void display(char s[])
{
    cout << "Entered char array is: " << s << endl;
}

void display(string s)
{
    cout << "Entered string is: " << s << endl;
}

Output

Enter a string:  Programming is fun.
Enter another string:  Really?
Entered string is: Programming is fun.
Entered char array is: Really?

In the above program, two strings are asked to enter. These are stored in str and str1 respectively, where str is a char array and str1 is a string object.

Then, we have two functions display() that outputs the string onto the string.

The only difference between the two functions is the parameter. The first display() function takes char array as a parameter, while the second takes string as a parameter.

This process is known as function overloading. Learn more about Function Overloading.

C++ Structures

C++ Structures

In this article, you'll learn about structures in C++ programming; what is it, how to define it and use it in your program.

Structure is a collection of variables of different data types under a single name. It is similar to a class in that, both holds a collecion of data of different data types.

For example: You want to store some information about a person: his/her name, citizenship number and salary. You can easily create different variables name, citNo, salary to store these information separately.

However, in the future, you would want to store information about multiple persons. Now, you'd need to create different variables for each information per person: name1, citNo1, salary1, name2, citNo2, salary2

You can easily visualize how big and messy the code would look. Also, since no relation between the variables (information) would exist, it's going to be a daunting task.

A better approach will be to have a collection of all related information under a single name Person, and use it for every person. Now, the code looks much cleaner, readable and efficient as well.

This collection of all related information under a single name Person is a structure.

How to declare a structure in C++ programming?

The struct keyword defines a structure type followed by an identifier (name of the structure).

Then inside the curly braces, you can declare one or more members (declare variables inside curly braces) of that structure. For example:

struct Person
{
    char name[50];
    int age;
    float salary;
};

Here a structure person is defined which has three members: name, age and salary.

When a structure is created, no memory is allocated.

The structure definition is only the blueprint for the creating of variables. You can imagine it as a datatype. When you define an integer as below:

int foo;

The int specifies that, variable foo can hold integer element only. Similarly, structure definition only specifies that, what property a structure variable holds when it is defined.

Note: Remember to end the declaration with a semicolon (;)

How to define a structure variable?

Once you declare a structure person as above. You can define a structure variable as:

Person bill;

Here, a structure variable bill is defined which is of type structure Person.

When structure variable is defined, only then the required memory is allocated by the compiler.

Considering you have either 32-bit or 64-bit system, the memory of float is 4 bytes, memory of int is 4 bytes and memory of char is 1 byte.

Hence, 58 bytes of memory is allocated for structure variable bill.

How to access members of a structure?

The members of structure variable is accessed using a dot (.) operator.

Suppose, you want to access age of structure variable bill and assign it 50 to it. You can perform this task by using following code below:

bill.age = 50;

Example: C++ Structure

C++ Program to assign data to members of a structure variable and display it.

#include <iostream>
using namespace std;

struct Person
{
    char name[50];
    int age;
    float salary;
};

int main()
{
    Person p1;

    cout << "Enter Full name: ";
    cin.get(p1.name, 50);
    cout << "Enter age: ";
    cin >> p1.age;
    cout << "Enter salary: ";
    cin >> p1.salary;

    cout << "\nDisplaying Information." << endl;
    cout << "Name: " << p1.name << endl;
    cout <<"Age: " << p1.age << endl;
    cout << "Salary: " << p1.salary;

    return 0;
}

Output

Enter Full name: Magdalena Dankova
Enter age: 27
Enter salary: 1024.4
Displaying Information.
Name: Magdalena Dankova
Age: 27
Salary: 1024.4

Here a structure Person is declared which has three members name, age and salary.

Inside main() function, a structure variable p1 is defined. Then, the user is asked to enter information and data entered by user is displayed.

You should also check out these structure related tutorials:

• How to pass structures to functions?
• How to use pointers with structures?

C++ Structure and Function

In this article, you'll find relevant examples to pass structures as an argument to a function, and use them in your program.

Structure variables can be passed to a function and returned in a similar way as normal arguments.

Passing structure to function in C++

A structure variable can be passed to a function in similar way as normal argument. Consider this example:

Example 1: C++ Structure and Function

#include <iostream>
using namespace std;

struct Person {
    char name[50];
    int age;
    float salary;
};

void displayData(Person);   // Function declaration

int main() {
    Person p;

    cout << "Enter Full name: ";
    cin.get(p.name, 50);
    cout << "Enter age: ";
    cin >> p.age;
    cout << "Enter salary: ";
    cin >> p.salary;

    // Function call with structure variable as an argument
    displayData(p);

    return 0;
}

void displayData(Person p) {
    cout << "\nDisplaying Information." << endl;
    cout << "Name: " << p.name << endl;
    cout <<"Age: " << p.age << endl;
    cout << "Salary: " << p.salary;
}

Output

Enter Full name: Bill Jobs
Enter age: 55
Enter salary: 34233.4
Displaying Information.
Name: Bill Jobs
Age: 55
Salary: 34233.4

In this program, user is asked to enter the name, age and salary of a Person inside main() function.

Then, the structure variable p is to passed to a function using.

displayData(p);

The return type of displayData() is void and a single argument of type structure Person is passed.

Then the members of structure p is displayed from this function.

Example 2: Returning structure from function in C++

#include <iostream>
using namespace std;

struct Person {
    char name[50];
    int age;
    float salary;
};

Person getData(Person); 
void displayData(Person); 

int main() {

    Person p, temp;

    temp = getData(p);
    p = temp;
    displayData(p);

    return 0;
}

Person getData(Person p) {

    cout << "Enter Full name: ";
    cin.get(p.name, 50);

    cout << "Enter age: ";
    cin >> p.age;

    cout << "Enter salary: ";
    cin >> p.salary;

    return p;
}

void displayData(Person p) {
    cout << "\nDisplaying Information." << endl;
    cout << "Name: " << p.name << endl;
    cout <<"Age: " << p.age << endl;
    cout << "Salary: " << p.salary;
}

The output of this program is the same as the program above.

In this program, we have created two structure variables p and temp of type Person under the main() function.

The structure variable p is passed to getData() function which takes input from the user which is then stored in the temp variable.

temp = getData(p); 

We then assign the value of temp to p.

p = temp;

Then the structure variable p is passed to displayData() function, which displays the information.

Note: We don't really need to use the temp variable for most compilers and C++ versions. Instead, we can simply use the following code:

p = getData(p);

C++ Pointers to Structure

In this article, you'll find relevant examples that will help you to work with pointers to access data within a structure.

A pointer variable can be created not only for native types like (int, float, double etc.) but they can also be created for user defined types like structure.

If you do not know what pointers are, visit C++ pointers.

Here is how you can create pointer for structures:

#include <iostream>
using namespace std;

struct temp {
    int i;
    float f;
};

int main() {
    temp *ptr;
    return 0;
}

This program creates a pointer ptr of type structure temp.

Example: Pointers to Structure

#include <iostream>
using namespace std;

struct Distance {
    int feet;
    float inch;
};

int main() {
    Distance *ptr, d;

    ptr = &d;

    cout << "Enter feet: ";
    cin >> (*ptr).feet;
    cout << "Enter inch: ";
    cin >> (*ptr).inch;

    cout << "Displaying information." << endl;
    cout << "Distance = " << (*ptr).feet << " feet " << (*ptr).inch << " inches";

    return 0;
}

Output

Enter feet: 4
Enter inch: 3.5
Displaying information.
Distance = 4 feet 3.5 inches

In this program, a pointer variable ptr and normal variable d of type structure Distance is defined.

The address of variable d is stored to pointer variable, that is, ptr is pointing to variable d. Then, the member function of variable d is accessed using pointer.