Education logo

C++

C++ and its uses

By Shri ValsanPublished about a year ago 38 min read
Like

C++ Tutorial

Learn C++

C++ is a popular programming language.

C++ is used to create computer programs and is one of the most used languages in game development.

Examples in Each Chapter

Our "Try it Yourself" editor makes it easy to learn C++. You can edit C++ code and view the result in your browser.

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!";

return 0;

}

We recommend reading this tutorial, in the sequence listed in the left menu.

C++ is an object-oriented language and some concepts may be new. Take breaks when needed, and go over the examples as many times as needed.

C++ Introduction

What is C++?

C++ is a cross-platform language that can be used to create high-performance applications.

C++ was developed by Bjarne Stroustrup, as an extension to the C language.

C++ gives programmers a high level of control over system resources and memory.

The language was updated 4 major times in 2011, 2014, 2017, and 2020 to C++11, C++14, C++17, and C++20.

Why Use C++

C++ is one of the world's most popular programming languages.

C++ can be found in today's operating systems, Graphical User Interfaces, and embedded systems.

C++ is an object-oriented programming language that gives a clear structure to programs and allows code to be reused, lowering development costs.

C++ is portable and can be used to develop applications that can be adapted to multiple platforms.

C++ is fun and easy to learn!

As C++ is close to C, C#, and Java, it makes it easy for programmers to switch to C++ or vice versa.

Difference between C and C++

C++ was developed as an extension of C, and both languages have almost the same syntax.

The main difference between C and C++ is that C++ supports classes and objects, while C does not.

C++ Getting Started

C++ Get Started

To start using C++, you need two things:

A text editor, like Notepad, to write C++ code

A compiler, like GCC, to translates the C++ code into a language that the computer will understand

There are many text editors and compilers to choose from. In this tutorial, we will use an IDE (see below).

C++ Install IDE

An IDE (Integrated Development Environment) is used to edit AND compile the code.

Popular IDE's include Code::Blocks, Eclipse, and Visual Studio. These are all free, and they can be used to both edit and debug C++ code.

Note: Web-based IDE's can work as well, but functionality is limited.

We will use Code::Blocks in our tutorial, which we believe is a good place to start.

You can find the latest version of Codeblocks at http://www.codeblocks.org/. Download the mingw-setup.exe file, which will install the text editor with a compiler.

C++ Quickstart

Let's create our first C++ file.

Open Codeblocks and go to File > New > Empty File.

Write the following C++ code and save the file as myfirstprogram.cpp (File > Save File as):

myfirstprogram.cpp

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!";

return 0;

}

Don't worry if you don't understand the code above - we will discuss it in detail in later chapters. For now, focus on how to run the code.

In Codeblocks, it should look like this:

Then, go to Build > Build and Run to run (execute) the program. The result will look something to this:

Result:

Hello World!

Process returned 0 (0x0) execution time : 0.011 s

Press any key to continue.

Congratulations! You have now written and executed your first C++ program.

Learning C++ At W3Schools

When learning C++ at W3Schools.com, you can use our "Try it Yourself" tool, which shows both the code and the result. This will make it easier for you to understand every part as we move forward:

myfirstprogram.cpp

Code:

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!";

return 0;

}

Result:

Hello World!

C++ Syntax

Let's break up the following code to understand it better:

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!";

return 0;

}

Example explained

Line 1: #include <iostream> is a header file library that lets us work with input and output objects, such as cout (used in line 5). Header files add functionality to C++ programs.

Line 2: using namespace std means that we can use names for objects and variables from the standard library.

Don't worry if you don't understand how #include <iostream> and using namespace std works. Just think of it as something that (almost) always appears in your program.

Line 3: A blank line. C++ ignores white space. But we use it to make the code more readable.

Line 4: Another thing that always appears in a C++ program, is int main(). This is called a function. Any code inside its curly brackets {} will be executed.

Line 5: cout (pronounced "see-out") is an object used together with the insertion operator (<<) to output/print text. In our example it will output "Hello World".

Note: Every C++ statement ends with a semicolon ;

Note: The body of int main() could also be written as:

int main () { cout << "Hello World! "; return 0; }

Remember: The compiler ignores white spaces. However, multiple lines make the code more readable.

Line 6: return 0 ends the main function.

Line 7: Do not forget to add the closing curly bracket } to actually end the main function.

Omitting Namespace

You might see some C++ programs that rus without the standard namespace library. The using namespace std line can be omitted and replaced with the std keyword, followed by the: operator for some objects:

Example

#include <iostream>

int main() {

std::cout << "Hello World!";

return 0;

}

It is up to you if you want to include the standard namespace library or not.

C++ Output (Print Text)

The cout object, together with the << operator, is used to output values/print text:

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!";

return 0;

}

You can add as many cout objects as you want. However, note that it does not insert a new line at the end of the output:

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!";

cout << "I am learning C++";

return 0;

}

C++ New Lines

New Lines

To insert a new line, you can use the \n character:

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World! \n";

cout << "I am learning C++";

return 0;

}

Tip: Two \n characters after each other will create a blank line:

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World! \n\n";

cout << "I am learning C++";

return 0;

}

Another way to insert a new line is with the end l manipulator:

Example

#include <iostream>

using namespace std;

int main() {

cout << "Hello World!" << endl;

cout << "I am learning C++";

return 0;

}

Both \n and end l are used to break lines. However, \n is the most used.

But what is \n exactly?

The newline character (\n) is called an escape sequence, and it forces the cursor to change its position to the beginning of the next line on the screen. This results in a new line.

Examples of other valid escape sequences are:

Escape Sequence DescriptionTry it

\t Creates a horizontal tab

\\ Inserts a backslash character (\)

\" Inserts a double quote character

C++ Comments

Comments can be used to explain C++ code, and to make it more readable. It can also be used to prevent execution when testing alternative code. Comments can be singled-lined or multi-lined.

Single-line Comments

Single-line comments start with two forward slashes (//).

Any text between // and the end of the line is ignored by the compiler (will not be executed).

This example uses a single-line comment before a line of code:

Example

// This is a comment

cout << "Hello World!";

This example uses a single-line comment at the end of a line of code:

Example

cout << "Hello World!"; // This is a comment

C++ Multi-line Comments

Multi-line comments start with /* and ends with */.

Any text between /* and */ will be ignored by the compiler:

Example

/* The code below will print the words Hello World!

to the screen, and it is amazing */

cout << "Hello World!";

Single or multi-line comments?

It is up to you which you want to use. Normally, we use // for short comments, and /* */ for longer.

C++ Variables

Variables are containers for storing data values.

In C++, there are different types of variables (defined with different keywords), for example:

int - stores integers (whole numbers), without decimals, such as 123 or -123

double - stores floating point numbers, with decimals, such as 19.99 or -19.99

char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes

string - stores text, such as "Hello World". String values are surrounded by double quotes

bool - stores values with two states: true or false

Declaring (Creating) Variables

To create a variable, specify the type and assign it a value:

Syntax

type variableName = value;

Where type is one of C++ types (such as int), and variableName is the name of the variable (such as x or myName). The equal sign is used to assign values to the variable.

To create a variable that should store a number, look at the following example:

Example

Create a variable called myNum of type int and assign it the value 15:

int myNum = 15;

cout << myNum;

You can also declare a variable without assigning the value, and assign the value later:

Example

int myNum;

myNum = 15;

cout << myNum;

Note that if you assign a new value to an existing variable, it will overwrite the previous value:

Example

int myNum = 15; // myNum is 15

myNum = 10; // Now myNum is 10

cout << myNum; // Outputs 10

Other Types

A demonstration of other data types:

Example

int myNum = 5; // Integer (whole number without decimals)

double myFloatNum = 5.99; // Floating point number (with decimals)

char myLetter = 'D'; // Character

string myText = "Hello"; // String (text)

bool myBoolean = true; // Boolean (true or false)

You will learn more about the individual types in the Data Types chapter.

Display Variables

The cout object is used together with the << operator to display variables.

To combine both text and a variable, separate them with the << operator:

Example

int myAge = 35;

cout << "I am " << myAge << " years old.";

Add Variables Together

To add a variable to another variable, you can use the + operator:

Example

int x = 5;

int y = 6;

int sum = x + y;

cout << sum;

C++ Declare Multiple Variables

Declare Many Variables

To declare more than one variable of the same type, use a comma-separated list:

Example

int x = 5, y = 6, z = 50;

cout << x + y + z;

One Value to Multiple Variables

You can also assign the same value to multiple variables in one line:

Example

int x, y, z;

x = y = z = 50;

cout << x + y + z;

C++ Identifiers

All C++ variables must be identified with unique names.

These unique names are called identifiers.

Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).

Note: It is recommended to use descriptive names in order to create understandable and maintainable code:

Example

// Good

int minutesPerHour = 60;

// OK, but not so easy to understand what m actually is

int m = 60;

The general rules for naming variables are:

  • Names can contain letters, digits and underscores
  • Names must begin with a letter or an underscore (_)
  • Names are case sensitive (myVar and myvar are different variables)
  • Names cannot contain whitespaces or special characters like !, #, %, etc.
  • Reserved words (like C++ keywords, such as int) cannot be used as names

C++ Constants

Constants

When you do not want others (or yourself) to change existing variable values, use the const keyword (this will declare the variable as "constant", which means unchangeable and read-only):

Example

const int myNum = 15; // myNum will always be 15

myNum = 10; // error: assignment of read-only variable 'myNum'

You should always declare the variable as constant when you have values that are unlikely to change:

Example

const int minutesPerHour = 60;

const float PI = 3.14;

C++ User Input

You have already learned that cout is used to output (print) values. Now we will use cin to get user input.

cin is a predefined variable that reads data from the keyboard with the extraction operator (>>).

In the following example, the user can input a number, which is stored in the variable x. Then we print the value of x:

Example

int x;

cout << "Type a number: "; // Type a number and press enter

cin >> x; // Get user input from the keyboard

cout << "Your number is: " << x; // Display the input value

Good To Know

cout is pronounced "see-out". Used for output, and uses the insertion operator (<<)

cin is pronounced "see-in". Used for input, and uses the extraction operator (>>)

Creating a Simple Calculator

In this example, the user must input two numbers. Then we print the sum by calculating (adding) the two numbers:

Example

int x, y;

int sum;

cout << "Type a number: ";

cin >> x;

cout << "Type another number: ";

cin >> y;

sum = x + y;

cout << "Sum is: " << sum;

There you go! You just built a basic calculator!

C++ Exercises

Test Yourself With Exercises

Exercise:

Use the correct keyword to get user input, stored in the variable x:

int x;

cout << "Type a number: ";

>>

;

C++ Data Types

C++ Data Types

As explained in the Variables chapter, a variable in C++ must be a specified data type:

Example

int myNum = 5; // Integer (whole number)

float myFloatNum = 5.99; // Floating point number

double myDoubleNum = 9.98; // Floating point number

char myLetter = 'D'; // Character

bool myBoolean = true; // Boolean

string myText = "Hello"; // String

Basic Data Types

The data type specifies the size and type of information the variable will store:

Data Type Size Description

boolean 1 byte Stores true or false values

char 1 byte Stores a single character/letter/number, or ASCII values

int 2 or 4 bytes Stores whole numbers, without decimals

float 4 bytes Stores fractional numbers, containing one or more decimals. Sufficient for storing 6-7 decimal digits

double 8 bytes Stores fractional numbers, containing one or more decimals. Sufficient for storing 15 decimal digits

You will learn more about the individual data types in the next chapters.

C++ Exercises

Test Yourself With Exercises

Exercise:

Add the correct data type for the following variables:

myNum = 9;

myDoubleNum = 8.99;

myLetter = 'A';

myBool = false;

myText = "Hello World";

C++ Numeric Data Types

Numeric Types

Use int when you need to store a whole number without decimals, like 35 or 1000, and float or double when you need a floating point number (with decimals), like 9.99 or 3.14515.

int

int myNum = 1000;

cout << myNum;

float

float myNum = 5.75;

cout << myNum;

double

double myNum = 19.99;

cout << myNum;

float vs. double

The precision of a floating point value indicates how many digits the value can have after the decimal point. The precision of float is only six or seven decimal digits, while double variables have a precision of about 15 digits. Therefore it is safer to use double for most calculations.

Scientific Numbers

A floating point number can also be a scientific number with an "e" to indicate the power of 10:

Example

float f1 = 35e3;

double d1 = 12E4;

cout << f1;

cout << d1;

C++ Boolean Data Types

Boolean Types

A boolean data type is declared with the bool keyword and can only take the values true or false.

When the value is returned, true = 1 and false = 0.

Example

bool isCodingFun = true;

bool isFishTasty = false;

cout << isCodingFun; // Outputs 1 (true)

cout << isFishTasty; // Outputs 0 (false)

C++ Character Data Types

Character Types

The char data type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c':

Example

char myGrade = 'B';

cout << myGrade;

Alternatively, you can use ASCII values to display certain characters:

Example

char a = 65, b = 66, c = 67;

cout << a;

cout << b;

cout << c;

C++ String Data Types

String Types

The string type is used to store a sequence of characters (text). This is not a built-in type, but it behaves like one in its most basic usage. String values must be surrounded by double quotes:

Example

string greeting = "Hello";

cout << greeting;

To use strings, you must include an additional header file in the source code, the <string> library:

Example

// Include the string library

#include <string>

// Create a string variable

string greeting = "Hello";

// Output string value

cout << greeting;

C++ Operators

Operators are used to performing operations on variables and values.

In the example below, we use the + operator to add together two values:

Example

int x = 100 + 50;

Although the + operator is often used to add together two values, like in the example above, it can also be used to add together a variable and a value, or a variable and another variable:

Example

int sum1 = 100 + 50; // 150 (100 + 50)

int sum2 = sum1 + 250; // 400 (150 + 250)

int sum3 = sum2 + sum2; // 800 (400 + 400)

C++ divides the operators into the following groups:

Arithmetic operators

Assignment operators

Comparison operators

Logical operators

Bitwise operators

Arithmetic Operators

Arithmetic operators are used to performing common mathematical operations.

Operator Name Description Example

+ Addition Adds together two values x + y

- Subtraction Subtracts one value from another x - y

* Multiplication Multiplies two values x * y

/ Division Divides one value by another x / y

% Modulus Returns the division remainder x % y

++ Increment Increases the value of a variable by 1 ++x

-- Decrement Decreases the value of a variable by 1 --x

C++ Exercises

Test Yourself With Exercises

Exercise:

Multiply 10 with 5, and print the result.

cout << 10 5;

C++ Assignment Operators

Assignment Operators

Assignment operators are used to assignimg values to variables.

In the example below, we use the assignment operator (=) to assign the value 10 to a variable called x:

Example

int x = 10;

The addition assignment operator (+=) adds a value to a variable:

Example

int x = 10;

x += 5;

A list of all assignment operators:

Operator Example Same As

= x = 5 x = 5

+= x += 3 x = x + 3

-= x -= 3 x = x - 3

*= x *= 3 x = x * 3

/= x /= 3 x = x / 3

%= x %= 3 x = x % 3

&= x &= 3 x = x & 3

|= x |= 3 x = x | 3

^= x ^= 3 x = x ^ 3

>>= x >>= 3 x = x >> 3

<<= x <<= 3 x = x << 3

C++ Comparison Operators

Comparison operators are used to comparing two values (or variables). This is important in programming because it helps us to find answers and make decisions.

The return value of a comparison is either 1 or 0, which means true (1) or false (0). These values are known as Boolean values, and you will learn more about them in the Booleans and If...Else chapter.

In the following example, we use the greater than operator (>) to find out if 5 is greater than 3:

Example

int x = 5;

int y = 3;

cout << (x > y); // returns 1 (true) because 5 is greater than 3

A list of all comparison operators:

Operator Name Example

== Equal to x == y

!= Not equal x != y

> Greater than x > y

< Less than x < y

>= Greater than or equal to x >= y

<= Less than or equal to x <= y

C++ Logical Operators

Logical Operators

As with comparison operators, you can also test for true (1) or false (0) values with logical operators.

C++ Strings

Strings are used for storing text.

A string variable contains a collection of characters surrounded by double quotes:

Example

Create a variable of type string and assign it a value:

string greeting = "Hello";

To use strings, you must include an additional header file in the source code, the <string> library:

Example

// Include the string library

#include <string>

// Create a string variable

string greeting = "Hello";

String Concatenation

The + operator can be used between strings to add them together to make a new string. This is called concatenation:

Example

string firstName = "John ";

string lastName = "Doe";

string fullName = firstName + lastName;

cout << fullName;

In the example above, we added a space after firstName to create a space between John and Doe on output. However, you could also add a space with quotes (" " or ' '):

Example

string firstName = "John";

string lastName = "Doe";

string fullName = firstName + " " + lastName;

cout << fullName;

Append

A string in C++ is actually an object, which contains functions that can perform certain operations on strings. For example, you can also concatenate strings with the append() function:

Example

string firstName = "John ";

string lastName = "Doe";

string fullName = firstName.append(lastName);

cout << fullName;

C++ Numbers and Strings

Adding Numbers and Strings

WARNING!

C++ uses the + operator for both addition and concatenation.

Numbers are added. Strings are concatenated.

If you add two numbers, the result will be a number:

Example

int x = 10;

int y = 20;

int z = x + y; // z will be 30 (an integer)

If you add two strings, the result will be a string concatenation:

Example

string x = "10";

string y = "20";

string z = x + y; // z will be 1020 (a string)

If you try to add a number to a string, an error occurs:

Example

string x = "10";

int y = 20;

string z = x + y;

C++ String Length

String Length

To get the length of a string, use the length() function:

Example

string txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

cout << "The length of the txt string is: " << txt.length();

Tip: You might see some C++ programs that use the size() function to get the length of a string. This is just an alias of length(). It is completely up to you if you want to use length() or size():

Example

string txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

cout << "The length of the txt string is: " << txt.size();

C++ Access Strings

Access Strings

You can access the characters in a string by referring to its index number inside square brackets [].

This example prints the first character in myString:

Example

string myString = "Hello";

cout << myString[0];

// Outputs H

Note: String indexes start with 0: [0] is the first character. [1] is the second character, etc.

This example prints the second character in myString:

Example

string myString = "Hello";

cout << myString[1];

// Outputs e

Change String Characters

To change the value of a specific character in a string, refer to the index number, and use single quotes:

Example

string myString = "Hello";

myString[0] = 'J';

cout << myString;

// Outputs Jello instead of Hello

C++ Special Characters

Strings - Special Characters

Because strings must be written within quotes, C++ will misunderstand this string, and generate an error:

string txt = "We are the so-called "Vikings" from the north.";

The solution to avoid this problem, is to use the backslash escape character.

The backslash (\) escape character turns special characters into string characters:

Escape character Result Description

\' ' Single quote

\" " Double quote

\\ \ Backslash

The sequence \" inserts a double quote in a string:

Example

string txt = "We are the so-called \"Vikings\" from the north.";

The sequence \' inserts a single quote in a string:

Example

string txt = "It\'s alright.";

The sequence \\ inserts a single backslash in a string:

Example

string txt = "The character \\ is called backslash.";

Other popular escape characters in C++ are:

Escape Character Result

\n New Line

\t Tab

C++ User Input Strings

User Input Strings

It is possible to use the extraction operator >> on cin to display a string entered by a user:

Example

string firstName;

cout << "Type your first name: ";

cin >> firstName; // get user input from the keyboard

cout << "Your name is: " << firstName;

// Type your first name: John

// Your name is: John

However, cin considers a space (whitespace, tabs, etc) as a terminating character, which means that it can only display a single word (even if you type many words):

Example

string fullName;

cout << "Type your full name: ";

cin >> fullName;

cout << "Your name is: " << fullName;

// Type your full name: John Doe

// Your name is: John

From the example above, you would expect the program to print "John Doe", but it only prints "John".

That's why, when working with strings, we often use the getline() function to read a line of text. It takes cin as the first parameter and the string variable as the second:

Example

string fullName;

cout << "Type your full name: ";

getline (cin, fullName);

cout << "Your name is: " << fullName;

// Type your full name: John Doe

// Your name is: John Doe

C++ String Namespace

Omitting Namespace

You might see some C++ programs that run without the standard namespace library. The using namespace std line can be omitted and replaced with the std keyword, followed by the :: operator for string (and cout) objects:

Example

#include <iostream>

#include <string>

int main() {

std::string greeting = "Hello";

std::cout << greeting;

return 0;

}

It is up to you if you want to include the standard namespace library or not.

C++ Math

C++ has many functions that allows you to perform mathematical tasks on numbers.

Max and min

The max(x,y) function can be used to find the highest value of x and y:

Example

cout << max(5, 10);

And the min(x,y) function can be used to find the lowest value of x and y:

Example

cout << min(5, 10);

C++ <cmath> Header

Other functions, such as sqrt (square root), round (rounds a number) and log (natural logarithm), can be found in the <cmath> header file:

Example

// Include the cmath library

#include <cmath>

cout << sqrt(64);

cout << round(2.6);

cout << log(2);

C++ Booleans

Very often, in programming, you will need a data type that can only have one of two values, like:

YES / NO

ON / OFF

TRUE / FALSE

For this, C++ has a bool data type, which can take the values true (1) or false (0).

Boolean Values

A boolean variable is declared with the bool keyword and can only take the values true or false:

Example

bool isCodingFun = true;

bool isFishTasty = false;

cout << isCodingFun; // Outputs 1 (true)

cout << isFishTasty; // Outputs 0 (false)

From the example above, you can read that a true value returns 1, and false returns 0.

However, it is more common to return a boolean value by comparing values and variables (see next page).

C++ Boolean Expressions

Boolean Expression

A Boolean expression returns a boolean value that is either 1 (true) or 0 (false).

This is useful to build logic, and find answers.

You can use a comparison operator, such as the greater than (>) operator, to find out if an expression (or variable) is true or false:

Example

int x = 10;

int y = 9;

cout << (x > y); // returns 1 (true), because 10 is higher than 9

Or even easier:

Example

cout << (10 > 9); // returns 1 (true), because 10 is higher than 9

In the examples below, we use the equal to (==) operator to evaluate an expression:

Example

int x = 10;

cout << (x == 10); // returns 1 (true), because the value of x is equal to 10

Example

cout << (10 == 15); // returns 0 (false), because 10 is not equal to 15

Real Life Example

Let's think of a "real life example" where we need to find out if a person is old enough to vote.

In the example below, we use the >= comparison operator to find out if the age (25) is greater than OR equal to the voting age limit, which is set to 18:

Example

int myAge = 25;

int votingAge = 18;

cout << (myAge >= votingAge); // returns 1 (true), meaning 25 year olds are allowed to vote!

Cool, right? An even better approach (since we are on a roll now), would be to wrap the code above in an if...else statement, so we can perform different actions depending on the result:

Example

Output "Old enough to vote!" if myAge is greater than or equal to 18. Otherwise output "Not old enough to vote.":

int myAge = 25;

int votingAge = 18;

if (myAge >= votingAge) {

cout << "Old enough to vote!";

} else {

cout << "Not old enough to vote.";

}

// Outputs: Old enough to vote!

Booleans are the basis for all C++ comparisons and conditions.

You will learn more about conditions (if...else) in the next chapter.

C++ If ... Else

C++ Conditions and If Statements

You already know that C++ supports the usual logical conditions from mathematics:

Less than: a < b

Less than or equal to: a <= b

Greater than: a > b

Greater than or equal to: a >= b

Equal to a == b

Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

C++ has the following conditional statements:

Use if to specify a block of code to be executed, if a specified condition is true

Use else to specify a block of code to be executed, if the same condition is false

Use else if to specify a new condition to test, if the first condition is false

Use switch to specify many alternative blocks of code to be executed

The if Statement

Use the if statement to specify a block of C++ code to be executed if a condition is true.

Syntax

if (condition) {

// block of code to be executed if the condition is true

}

Note that if is in lowercase letters. Uppercase letters (If or IF) will generate an error.

In the example below, we test two values to find out if 20 is greater than 18. If the condition is true, print some text:

Example

if (20 > 18) {

cout << "20 is greater than 18";

}

We can also test variables:

Example

int x = 20;

int y = 18;

if (x > y) {

cout << "x is greater than y";

}

Example explained

In the example above we use two variables, x and y, to test whether x is greater than y (using the > operator). As x is 20, and y is 18, and we know that 20 is greater than 18, we print to the screen that "x is greater than y".

C++ Else

The else Statement

Use the else statement to specify a block of code to be executed if the condition is false.

Syntax

if (condition) {

// block of code to be executed if the condition is true

} else {

// block of code to be executed if the condition is false

}

Example

int time = 20;

if (time < 18) {

cout << "Good day.";

} else {

cout << "Good evening.";

}

// Outputs "Good evening."

Example explained

In the example above, time (20) is greater than 18, so the condition is false. Because of this, we move on to the else condition and print to the screen "Good evening". If the time was less than 18, the program would print "Good day".

C++ Else If

The else if Statement

Use the else if statement to specify a new condition if the first condition is false.

Syntax

if (condition1) {

// block of code to be executed if condition1 is true

} else if (condition2) {

// block of code to be executed if the condition1 is false and condition2 is true

} else {

// block of code to be executed if the condition1 is false and condition2 is false

}

Example

int time = 22;

if (time < 10) {

cout << "Good morning.";

} else if (time < 20) {

cout << "Good day.";

} else {

cout << "Good evening.";

}

// Outputs "Good evening."

Example explained

In the example above, time (22) is greater than 10, so the first condition is false. The next condition, in the else if statement, is also false, so we move on to the else condition since condition1 and condition2 is both false - and print to the screen "Good evening".

However, if the time was 14, our program would print "Good day."

C++ Short Hand If Else

Short Hand If...Else (Ternary Operator)

There is also a short-hand if else, which is known as the ternary operator because it consists of three operands. It can be used to replace multiple lines of code with a single line. It is often used to replace simple if else statements:

Syntax

variable = (condition) ? expressionTrue : expressionFalse;

Instead of writing:

Example

int time = 20;

if (time < 18) {

cout << "Good day.";

} else {

cout << "Good evening.";

}

You can simply write:

Example

int time = 20;

string result = (time < 18) ? "Good day." : "Good evening.";

cout << result;

C++ Switch Statements

Use the switch statement to select one of many code blocks to be executed.

Syntax

switch(expression) {

case x:

// code block

break;

case y:

// code block

break;

default:

// code block

}

This is how it works:

The switch expression is evaluated once

The value of the expression is compared with the values of each case

If there is a match, the associated block of code is executed

The break and default keywords are optional, and will be described later in this chapter

The example below uses the weekday number to calculate the weekday name:

Example

int day = 4;

switch (day) {

case 1:

cout << "Monday";

break;

case 2:

cout << "Tuesday";

break;

case 3:

cout << "Wednesday";

break;

case 4:

cout << "Thursday";

break;

case 5:

cout << "Friday";

break;

case 6:

cout << "Saturday";

break;

case 7:

cout << "Sunday";

break;

}

// Outputs "Thursday" (day 4)

The break Keyword

When C++ reaches a break keyword, it breaks out of the switch block.

This will stop the execution of more code and case testing inside the block.

When a match is found, and the job is done, it's time for a break. There is no need for more testing.

A break can save a lot of execution time because it "ignores" the execution of all the rest of the code in the switch block.

The default Keyword

The default keyword specifies some code to run if there is no case match:

Example

int day = 4;

switch (day) {

case 6:

cout << "Today is Saturday";

break;

case 7:

cout << "Today is Sunday";

break;

default:

cout << "Looking forward to the Weekend";

}

// Outputs "Looking forward to the Weekend"

C++ While Loop

C++ Loops

Loops can execute a block of code as long as a specified condition is reached.

Loops are handy because they save time, reduce errors, and they make code more readable.

C++ While Loop

The while loop loops through a block of code as long as a specified condition is true:

Syntax

while (condition) {

// code block to be executed

}

In the example below, the code in the loop will run, over and over again, as long as a variable (i) is less than 5:

Example

int i = 0;

while (i < 5) {

cout << i << "\n";

i++;

}

Note: Do not forget to increase the variable used in the condition, otherwise the loop will never end!

C++ Do/While Loop

The Do/While Loop

The do/while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

Syntax

do {

// code block to be executed

}

while (condition);

The example below uses a do/while loop. The loop will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested:

Example

int i = 0;

do {

cout << i << "\n";

i++;

}

while (i < 5);

Do not forget to increase the variable used in the condition, otherwise, the loop will never end!

C++ For Loop

When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop:

Syntax

for (statement 1; statement 2; statement 3) {

// code block to be executed

}

Statement 1 is executed (one time) before the execution of the code block.

Statement 2 defines the condition for executing the code block.

Statement 3 is executed (every time) after the code block has been executed.

The example below will print the numbers 0 to 4:

Example

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

cout << i << "\n";

}

Example explained

Statement 1 sets a variable before the loop starts (int i = 0).

Statement 2 defines the condition for the loop to run (i must be less than 5). If the condition is true, the loop will start over again, if it is false, the loop will end.

Statement 3 increases a value (i++) each time the code block in the loop has been executed.

Another Example

This example will only print even values between 0 and 10:

Example

for (int i = 0; i <= 10; i = i + 2) {

cout << i << "\n";

}

Nested Loops

It is also possible to place a loop inside another loop. This is called a nested loop.

The "inner loop" will be executed one time for each iteration of the "outer loop":

Example

// Outer loop

for (int i = 1; i <= 2; ++i) {

cout << "Outer: " << i << "\n"; // Executes 2 times

// Inner loop

for (int j = 1; j <= 3; ++j) {

cout << " Inner: " << j << "\n"; // Executes 6 times (2 * 3)

}

}

The for-each Loop

There is also a "for-each loop" (introduced in C++ version 11 (2011), which is used exclusively to loop through elements in an array (or other data sets):

Syntax

for (type variableName : arrayName) {

// code block to be executed

}

The following example outputs all elements in an array, using a "for-each loop":

Example

int myNumbers[5] = {10, 20, 30, 40, 50};

for (int i : myNumbers) {

cout << i << "\n";

}

Note: Don't worry if you don't understand the example above. You will learn more about arrays in the C++ Arrays chapter.

C++ Break and Continue

C++ Break

You have already seen the break statement used in an earlier chapter of this tutorial. It was used to "jump out" of a switch statement.

The break statement can also be used to jump out of a loop.

This example jumps out of the loop when i is equal to 4:

Example

for (int i = 0; i < 10; i++) {

if (i == 4) {

break;

}

cout << i << "\n";

}

C++ Continue

The continue statement breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop.

This example skips the value of 4:

Example

for (int i = 0; i < 10; i++) {

if (i == 4) {

continue;

}

cout << i << "\n";

}

Break and Continue in While Loop

You can also use a break and continue in while loops:

Break Example

int i = 0;

while (i < 10) {

cout << i << "\n";

i++;

if (i == 4) {

break;

}

}

Continue Example

int i = 0;

while (i < 10) {

if (i == 4) {

i++;

continue;

}

cout << i << "\n";

i++;

}

C++ Arrays

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.

To declare an array, define the variable type, specify the name of the array followed by square brackets and specify the number of elements it should store:

string cars[4];

We have now declared a variable that holds an array of four strings. To insert values to it, we can use an array literal - place the values in a comma-separated list, inside curly braces:

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};

To create an array of three integers, you could write:

int myNum[3] = {10, 20, 30};

Access the Elements of an Array

You access an array element by referring to the index number inside square brackets [].

This statement accesses the value of the first element in cars:

Example

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};

cout << cars[0];

// Outputs Volvo

Note: Array indexes start with 0: [0] is the first element. [1] is the second element, etc.

Change an Array Element

To change the value of a specific element, refer to the index number:

cars[0] = "Opel";

Example

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};

cars[0] = "Opel";

cout << cars[0];

// Now outputs Opel instead of Volvo

C++ Arrays and Loops

Loop Through an Array

You can loop through the array elements with the for loop.

The following example outputs all elements in the cars array:

Example

string cars[5] = {"Volvo", "BMW", "Ford", "Mazda", "Tesla"};

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

cout << cars[i] << "\n";

}

This example outputs the index of each element together with its value:

Example

string cars[5] = {"Volvo", "BMW", "Ford", "Mazda", "Tesla"};

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

cout << i << " = " << cars[i] << "\n";

}

And this example shows how to loop through an array of integers:

Example

int myNumbers[5] = {10, 20, 30, 40, 50};

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

cout << myNumbers[i] << "\n";

}

The for-each Loop

There is also a "for-each loop" (introduced in C++ version 11 (2011), which is used exclusively to loop through elements in an array:

Syntax

for (type variableName : arrayName) {

// code block to be executed

}

The following example outputs all elements in an array, using a "for-each loop":

Example

int myNumbers[5] = {10, 20, 30, 40, 50};

for (int i : myNumbers) {

cout << i << "\n";

}

C++ Omit Array Size

Omit Array Size

In C++, you don't have to specify the size of the array. The compiler is smart enough to determine the size of the array based on the number of inserted values:

string cars[] = {"Volvo", "BMW", "Ford"}; // Three arrays

The example above is equal to:

string cars[3] = {"Volvo", "BMW", "Ford"}; // Also three arrays

However, the last approach is considered as "good practice", because it will reduce the chance of errors in your program.

Omit Elements on Declaration

It is also possible to declare an array without specifying the elements on the declaration, and add them later:

Example

string cars[5];

cars[0] = "Volvo";

cars[1] = "BMW";

...

trade schoolteacherstudentinterviewhow tohigh schooldegreecoursescollege
Like

About the Creator

Shri Valsan

Reader insights

Be the first to share your insights about this piece.

How does it work?

Add your insights

Comments

There are no comments for this story

Be the first to respond and start the conversation.

Sign in to comment

    Find us on social media

    Miscellaneous links

    • Explore
    • Contact
    • Privacy Policy
    • Terms of Use
    • Support

    © 2024 Creatd, Inc. All Rights Reserved.