C++ Tutorial | Learn C++ Programming Language

Built as an extension of C, C++ is one of the most used and powerful programming languages that supports classes. Hence, features such as object-oriented programming can be easily adopted by C++ which helps in creating complex programs. It allows developers to create highly efficient software. It has been extensively used to develop competitive applications such as gaming systems or systems software.

This guide is about programming in CPP. It covers the use of variables, data types, control statements, and many other concepts. Also, this guide covers some advanced topics like OOP concepts (object class inheritance), templates, and STL. Overall, reading this will help you develop skills as a beginner or assist in polishing your C++ skills.

Overview of C++

Developed by  Bjarne Stroustrup in 1979, C++ works as a general-purpose programming language which was an extension of C language. It supports object-oriented programming and complex coding and provides flexible and efficient system programming. Both low-level and high-level programming is supported by C++. Therefore, it is used in designing applications that range from operating systems to video games.

C++ can be directly used on different types of hardware resources and provides a rich feature set. This makes it one of the most used and successful programming languages worldwide.

History of C++

In the table below, we have covered the history of C++.

Some key features associated with C++ include the following:

• Object-Oriented Programming: Important features like class, structures, objects, inheritance, polymorphism, encapsulation, and abstraction are supported by C++.
• Performance: C++ delivers high performance due to its close-to-hardware properties.
• Portability: With little or no changes in code written in C++, it works on various platforms.
• Standard Library: A good number of useful functions for manipulating data structures, such as algorithms, are provided by default in C++.
• Memory Management: C++ provides both automatic and manual memory management capabilities through dynamic allocation and deallocation.

Applications of C++

C++ is widely used to develop software for various industries, and we have covered some use cases below.

• System Software: Operating systems, device drivers as well as embedded systems are built using C++.
• Game Development: C++ helps in the gaming industry by developing game engines and high-performance graphics.
• GUI Applications: Desktop applications with graphical user interfaces can be developed using C++.
• Financial Systems: High-speed computations are required in most financial applications, which is why they mostly use C++.
• Scientific Research: C++ is employed in simulations, real-time systems, and other scientific research applications.

Basics of C++

First C++ Program

Let’s jump onto writing a very simple “Hello, World!” program to the screen.

Example:

In this code, the first line includes the ‘iostream’ library using the ‘#include’ preprocessor. It is used to perform the input-output operations.

Next, we have defined the ‘main()’ method in the second line. This is where the compiler starts compiling the code.

The third line indicates the printing method in C++ to print the output ‘Hello, World!’ string in the output console. At last, we return the integer 0 to terminate the program.

Output:

C++ Comments

Comments are used to explain the code and make it more readable. They are ignored by the compiler, so they don’t affect the program’s execution.

There are two types of comments in C++:

• Single-line comments: Start with // and extend to the end of the line.

// This is a single-line comment

std::cout << “Hello, World!” << std::endl; // Prints a message

• Multi-line comments: Start with /* and end with */. They can span multiple lines.

/* This is a multi-line comment

It can span multiple lines */

std::cout << “Hello, World!” << std::endl;

C++ Identifiers

Identifiers are names given to various elements in a program, such as variables, functions, arrays, and more. They are used to identify these elements within the code.

Here are the rules for naming identifiers in C++:

1. Identifiers can include letters (both uppercase and lowercase), digits, and underscores.
2. They must begin with a letter or an underscore.
3. Identifiers are case-sensitive (myVariable and myvariable are different).
4. Keywords cannot be used as identifiers.

Examples of valid identifiers:

int age;

float salary;

char first_name;

Examples of invalid identifiers:

int 1stNumber; // Cannot start with a digit

float my-salary; // Cannot contain hyphen

char class; // Cannot use a keyword

Variables and Constants in C++

C++ Variables

Variables are commonly used to store data during the execution of a program. Here data can be changed dynamically, and each variable holds a specific type of data it can hold.

Here’s how to declare and initialise variables in C++:

int age = 25; // Integer variable

float salary = 50000.50; // Floating-point variable

char grade = ‘A’; // Character variable

Here, ‘int’, ‘float’, ‘char’, etc., are the data types of the ‘age’, ‘salary’, and ‘grade’ variables, respectively.

C++ Constants

Constants are variables whose values cannot be changed once they are initialised. They are defined using the const keyword.

Here’s how to declare constants in C++:

const int MAX_AGE = 100; // Constant integer

const float PI = 3.14; // Constant float

const char NEWLINE = ‘n’; // Constant character

Using constants helps in making your code more readable and maintainable, as the value of the constant is set once and cannot be modified later.

Scope of C++ Variables

The scope of a variable refers to the region of a program where that variable can be accessed. In C++, there are two types of scopes:

• Local Scope: These are the variables that are declared within a function or block having local scope. Thus, they can only be accessed from within that function or block.
• Global Scope: Those variables that are declared outside all functions have global scope. Hence, they can be accessed from any part of the program.

C++ Static Variables

Static variables in C++ have a limited scope for the function where they are initialised and retain their value even after function execution is completed.

Here’s how to declare a static variable in a function:

Output:

We can see, in the output, the counter variable has retained value between function calls after it is initialised. Therefore, static variables are commonly used to maintain the state information between function calls.

Data Types in C++

Data types in C++ specify the type of data that a variable can hold. They are essential for defining the operations that can be performed on the data and the amount of memory allocated for the data.

In C++, data types can be broadly categorised into three types:

• Primary Data Types
• Derived Data Types
• User-Defined Data Types.

Type Casting in C++

Type casting involves converting one data type into another.

In C++, type casting falls into two categories – implicit and explicit casting.

• Implicit Type Casting: Also called automatic type conversion, this kind of type casting is done by the compiler without any instruction from the programmer’s end. The compiler converts smaller data types into larger ones automatically so as to avoid data loss. 

Example:

int a = 42;

double b = a; // Implicit conversion from int to double

• Explicit Type Casting: Explicit type casting, also known as type conversion, requires the programmer to specify the type conversion. This is done using the cast operator.

Example:

double a = 42.56;

int b = (int)a; // Explicit conversion from double to int

Operators in C++

Operators are special symbols that perform operations on variables and values, which helps to manipulate data and variables. They provide a wide range of functions (from basic arithmetic to complex logic operators).

C++ provides a variety of operators, which can be categorised based on their functionality. Below is a table summarising the different types of operators available in C++.

Input/Output in C++

Input and output (I/O) operations in C++ are essential for interacting with users and external systems. The C++ Standard Library provides a set of functions and objects to handle I/O operations efficiently.

Input using cin

The cin object is used to read input from the standard input device, usually the keyboard. The >> operator is used to extract the data from cin.

Example:

Output using cout

The cout object is used to print output to the standard output device, usually the screen. The << operator is used to send the data to cout.

Example:

Output:

Control Statements in C++

The Control statements in C++ are mainly used to manage the flow of execution of a program. Features like repeating operations, jumping to different parts of code, task-making decisions, etc. are primary tasks of control statements.

C++ Decision Making

Depending upon a specific condition (true or false), the decision-making helps to execute such conditions. If, else, switch are the most commonly used decision-making statements in C++.

• if statement: Code will be executed only if the specified condition is true.
• else if statement: It adds a condition to check if the initial if condition returns false.
• else statement: Executed when none of the above conditions returned true.
• switch statement: A switch statement supports multiple decision statements at once and also supports jumping to multiple paths based upon its value.

Example of the if-else statement:

Here, we have printed different statements using the value of the age variable and checking if it is greater than or equal to 18

Output:

C++ Loops

C++ loop is one of the most important key features in the entire programming language because it helps to repeat a particular block of code in some finite number. Three types of loops are mentioned below

• for loop: When the number of iterations is known, a for loop is used.
• while loop: This loop runs infinite times and breaks until and unless a condition becomes false. It is mainly used when there is no knowledge of a specific number of iterations.
• do-while loop: This is almost similar to a while loop with one change, i.e. an initial condition is checked before running that code block in repetition. Hence, it is a control flow statement that stops execution depending upon a given boolean condition.

Example of for loop:

In the code below, we use the for-loop to print 1 to 5 values.

Output:

Functions in C++

Functions in C++ perform a specific given task using inputs, arguments, parameters, type of data types, etc., and return an output based upon the code block conditions. Functions mainly help in making reusable code, which is both time-saving and makes code organisation friendly.

Defining and Calling Functions

Here’s what you need to do for defining and calling functions.

This is the basic example of a function that adds two numbers by specifying return type, name, and parameters. In this, int add (int a, int b) is a function taking two integers a and b, returning its sum.

• Inline Functions: You can define inline functions using the inline keyword so that the compiler inserts the function’s code directly at the end of each call.
• Lambda Functions: These are the anonymous functions defined through the [] syntax. They are introduced in c++11 and often used for short snippets of code.

Example of a lambda function:

In the given code below, the ‘add’ function adds two integers and returns their sum. Lambda functions are used for quick temporary function creation and do not need a separate name definition.

Pointers and References in C++

Pointers in C++ are mainly used for efficient memory allocation and manipulation. Hence, they are among the most powerful features in C++.

Pointers

In brief, the pointers are the variables that can store the memory address of another variable. Thus, they are used for dynamic memory allocation, accessing array elements, and passing large structures or arrays to functions efficiently.

• Declaring and Using Pointers: To declare a pointer, you use the asterisk (*) symbol. To access the value at the memory address stored in the pointer, you use the dereference operator (&).

Example:

In this example, ptr is a pointer to var. The & operator is used to get the address of var, and *ptr is used to get the value at that address.

Output:

References

Alternative to pointers, a reference is a way to create an alias for another variable. References are generally safer and easier due to the fact that they do not require dereferencing, and they cannot be null.

• Declaring and Using References: Here, you should use the ampersand (&) symbol for the initialisation of reference, and then it cannot be changed to refer to another variable.

Arrays in C++

Arrays are used to store multiple values of the same type in a single variable. They provide a way to organise data efficiently and allow easy access to each element.

Declaring and Initializing Arrays

One of the most common tasks is declaring and initialising arrays, and it can be done by specifying the type, name, and number of elements in square brackets.

Example:

In the given example, an array of 5 integers is created, named ‘numbers’. The total size of the array while initialisation is 3.

Output:

Strings in C++

Strings in C++ are sequences of characters used to represent text. There are multiple ways to handle strings which include C-style Strings and the std::string class from its library.

• C-Style Strings: they are arrays of characters ending with a null character (0). They are the traditional way of handling strings in C and C++.
• std::string Class: The std::string class brings a more convenient way to work with strings through many built-in functions for string manipulation.

Creating and Using std::string:

In this example, the greeting is a std::string object. We demonstrate concatenation, getting the length of the string and outputting the string.

Output:

Structures and Union in C++

Structures can be defined as the data types which allow the grouping of different structures and unions using a single name so that it can create complex data..

• Structures: Structures (struct) in C++ are used to group variables of different types together. Each variable in a structure is called a member.

Defining and Using Structures:

In this example, the Person structure groups together a string (name), an integer (age), and a float (height) variables. We create an instance of Person, assign values to its members, and print them.

Output:

• Unions: Note that the unions in C++ are likely similar to the structures but with key differences. Hence, at a time, a union can hold only one of its members.

Dynamic Memory Management in C++

Dynamic memory management in C++ involves allocating and deallocating memory during runtime. This allows for flexible memory usage and efficient management of resources. The primary functions used for dynamic memory management are new and delete.

• Allocating Memory with new: This can be used to allocate memory dynamically for a single variable or an array of variables. It returns a pointer to the allocated memory.

Example:

int* ptr = new int; // Allocates memory for a single integer

int* arr = new int[10]; // Allocates memory for an array of 10 integers

• Deallocating Memory with delete: To deallocate the previously allocated memory with the new one, the delete operator is used, which is also important to prevent memory loss.

Example:

delete ptr; // Deallocates memory for the single integer

delete[] arr; // Deallocates memory for the array of integers

Object-Oriented Programming in C++

Object-Oriented Programming (OOP) is a programming paradigm that uses objects and classes to structure software programs. C++ supports OOP, which helps in organising complex programs into simpler, reusable components.

Classes and Objects

Classes are user-defined types that represent blueprints for objects. Objects are instances of classes.

Example:

Here, a Car is a class formed with two attributes (brand and year) and a method (displayInfo). myCar is an object of the Car class.

Output:

Encapsulation

Encapsulation restricts the direct access to some of the object’s components and can bundle data in a single unit (class) to prevent data modification.

Inheritance

Inheritance is the best example of code reusability, where a child class (subclass) is derived from its parent class (superclass) using their components. This promotes code reliability and also helps in assessing complex coding.

Polymorphism

Polymorphism allows its methods to conduct different things based on the property of the object it is acting upon. This includes compile-time polymorphism (method overloading) and runtime polymorphism (method overriding).

Abstraction

As the name suggests, abstraction is used to abstract or hide complex implementation details in a complex code. Hence, it helps in reducing the overall complexity of the program.

Function Overloading in C++

To have the same name with different parameters in any function, function overloading is used.

Example:

For example, the print function below is overloaded so that it can handle both integer and double inputs.

Output:

Operator Overloading in C++

Operator overloading in C++ allows developers to define custom behaviour for operators when they are used with user-defined types (classes). This makes objects of these classes behave more like built-in types.

Example:

In this example, the + operator is overloaded to add two Complex numbers. This allows the + operator to be used with complex objects just like with built-in types.

Output:

Virtual Functions in C++

The basic need for virtual functions in C++ is to ensure that the function called is correct, regardless of the type of reference or pointer used to call. Hence, virtual functions can be overridden in derived classes. This allows for dynamic (runtime) polymorphism, enabling more flexible and reusable code.

Rules for Virtual Functions

1. Declaration: Use the virtual keyword in the base class.
2. Override: In the derived class, the function signature must match the base class’s virtual function.
3. Base Class Pointer: Using a base class pointer or reference, call the overridden function.
4. Destructors: Every virtual function must have a virtual destructor to avoid memory leakage and properly clean up derived class objects.

Exception Handling in C++

In C++, the basic way to manage errors and all exceptions is to use exception handling. It helps to maintain the normal flow of the program, simultaneously dealing with exceptions and unexpected errors.

Key Components

1. Try block: Encloses the code that may throw an exception.
2. Catch block: Catches and handles the exception.
3. throw keyword: Used to throw an exception.

Example:

In this example:

• The try block contains code that may cause an exception.
• Throw keyword throws an exception whenever someone attempts a division by zero.
• The catch block handles the exception, preventing the program from crashing.

Files and Streams in C++

Files and streams in C++ handle input and output operations with external files, enabling data storage and retrieval.

C++ uses classes from the <fstream> library for file operations:

• ifstream: For reading from files.
• ofstream: For writing to files.
• fstream: For both reading and writing.

Key Concepts

So you can effectively manage file operations in C++, using these classes and methods.

Templates in C++

Templates in C++ provide a powerful mechanism for creating generic and reusable code. They allow functions and classes to operate with different data types without being rewritten for each type.

Function Templates

Function templates enable you to define a generic function that works with any data type. The actual data type is specified when the function is called.

Syntax:

Class Templates

Class templates allow you to define a generic class. Similar to function templates, the actual data type is specified when an object of the class is created.

Syntax:

STL in C++

Ever wondered about an inbuilt set of template classes and functions to provide your code with common data structure codes? The Standard Template Library (STL) offers ready-to-use components or reusable code snippets in C++ to make your work easy.

Key Components of STL

Iterators in C++

Iterators in C++ allow multiple traversals through the same code block by providing a common interface for iterating different types of elements throughout the function.

Types of Iterators

• Input Iterators: Read elements from a sequence.
• Output Iterators: Write elements to a sequence.
• Forward Iterators: Traverse a sequence in a single pass (read/write).
• Bidirectional Iterators: These iterators can traverse a sequence in both forward and backward directions.
• Random Access Iterators: Directly access any element within a sequence.

Example of Using Iterators:

In this example, There is an iterator for the vector<int> container. When we use the for loop, it uses the iterator to traverse and print each element in a numbers vector simultaneously.

Output:

Preprocessors in C++

Before the actual compilation of the code, the preprocessor directives are used, providing instructions to the compiler on what to preprocess in the source code before compiling. To start a preprocessor directive, you can use the # symbol, which can also be used to include files, define constants, and compile conditionally.

Key Preprocessor Directives

C vs C++

C is a procedural programming language that does not support classes. On the other hand, C++ is an extension of C that includes object-oriented features.

C++ vs Java

Both C++ and Java have their own benefits that users can use for different purposes. C++ can hold more complex code in object-oriented programming and also help in increasing performance efficiency. While Java is designed for portability and ease of use.

Advantages and Disadvantages of C++

C++ offers a balance of high performance and rich feature sets but comes with complexity and potential pitfalls.

Conclusion

C++ is thought to be a versatile and powerful programming language that builds upon the C foundation. It has robust features like object-oriented programming and strong standard libraries. C++ can be a very high-performance programming language, making it perfect to use for complex applications like system software development or game development. You can learn more about functions, pointers, control statements, data types, STL, etc. through this article.