Getting our machines set up for C++ development, and introducing the fundamental building blocks of programming - variables.

Getting our computer set up so we can create and build C++ programs. Then, creating our very first application

Setting up a C++ Development Environment

An introduction to the building blocks of our software - objects, and the variables that can be associated with them.

Objects, Variables and Types

Creating variables to store and update the data that describes our objects.  We also introduce comments, allowing us to describe our code in plain language.

Creating Variables

An introduction to the different types of numbers in C++, and how we can do basic math operations on them.

Numbers

An overview of the fundamental true or false data type, how we can create them, and how we can combine them.

Booleans - `true` and `false` values

Explore how C++ programs store and manage numbers in computer memory, including integer and floating-point types, memory allocation, and overflow handling.

Types and Literals

Creating a tiny program using numbers and booleans, then adding some breakpoints so we can step through our code in a debugger.

Introduction to Debugging

Types and Variables

Discover how we can package our code into reusable functions that we can easily call.  Then, learn how we can use conditionals and loops to control the flow of our program.

An introduction to functions - reusable blocks of code that we can use to break our application into smaller pieces.

Creating and Calling Functions

An introduction to how our function calls create a call stack, and how we can navigate it in a debugger.

The Call Stack and Debugging Functions

Use booleans and if statements to make our functions and programs more dynamic, choosing different execution paths.

Conditional Logic

Learn an alternative way to write conditionals, which is often used when we want to take different paths based on a specific value

Switch Statements

Allow our functions to communicate with their caller by returning values when they complete

Function `return` Statements

Going into more depth on what is happening when a variable is used as a different type

Implicit Conversions and Narrowing Casts

Making our functions more useful and dynamic by providing them with additional values to use in their execution

Function Arguments and Parameters

Learn more about how and when we can access variables, by understanding the importance of the scope in which they exist.

Scope

Understand what function prototypes are, and learn how we can use them to let us order our code any way we want.

Forward Declarations

Learn how we can use loops to iterate over a block of code, executing it as many times as needed.

Loops

Learn how we can use the modulus operator to get the remainder of integer division, and some common use cases.

The Modulus Operator (`%`)

Put everything we've learned in this chapter to the test by creating a C++ version of the Fizz Buzz game.

Fizz Buzz

Learn how the `&&` and `||` operators are optimized with short-circuit evaluation, only evaluating expressions when necessary

Short-circuit Evaluation

Functions, Conditionals and Loops

Classes and structs are the fundamental feature of object oriented programming.  In this chapter, we will see how we can set them up, and how we can use them to create the custom types our program needs.

Learn how to define, instantiate, and utilize classes, understanding how they form the backbone of object-oriented programming.

Abstraction and Classes

A guide to encapsulation, class invariants, and controlling data access with `public` and `private` specifiers.

Encapsulation and Access Specifiers

Learn about special functions we can add to our classes, control how our objects get created and destroyed.

Constructors and Destructors

Discover the role of structs, how they differ from classes, and how to initialize them without requiring a constructor.

Structs and Aggregate Initialization

This lesson introduces operator overloading, a fundamental concept to create more intuitive and readable code by customizing operators for user-defined types

Operator Overloading

This lesson introduces Structured Binding, a handy tool for unpacking simple data structures

Structured Binding

Classes and Structs

See how we can use inheritance to organise our classes into a hierarchy, unlocking a massive range of possibilities for building more complex software

In this lesson, we explore C++ inheritance, guiding you through creating and managing class hierarchies to streamline your code

Inheritance

Learn about `protected` class members in C++, including how and when to use them in your code, especially in the context of inheritance and class design

Protected Class Members

This lesson introduces Member Initializer Lists, focusing on their advantages for performance and readability, and how to use them effectively

Member Initializer Lists

This lesson provides an in-depth exploration of using inherited methods and variables in C++, covering constructor calls, variable modification, and function shadowing

Working with Inherited Members

An introduction to working with memory, and how we represent memory locations using references and pointers

This lesson introduces references, explaining how they work, their benefits, and their role in performance and data manipulation

References

This lesson provides a thorough introduction to pointers in C++, covering their definition, usage, and the distinction between pointers and references

Pointers

Learn about the `this` pointer in C++ programming, focusing on its application in identifying callers, chaining functions, and overloading operators.

The `this` Pointer

Learn about an important consideration when returning pointers and references from functions

Dangling Pointers and References

Memory, References and Pointers

An introduction to polymorphism - the key tool that let us build more complex programs whilst keeping our code simple.

This lesson provides an in-depth look at function overloading in C++, covering its importance, implementation, and best practices

Function Overloading

Explore the concept of static casting in C++, including examples and best practices for converting data types at compile time

Static Casting

This lesson provides an introduction to virtual functions and overrides, focusing on their role in enabling runtime polymorphism

Virtual Functions and Overrides

Get to grips with downcasting in C++, including static and dynamic casts. This lesson provides clear explanations and practical examples for beginners

Downcasting

Polymorphism

Go deeper on what is happening when we build our software.  Learn how we can use the preprocessor to automatically modify our source code before it is compiled, and how the linker connects our program together.

Explore the essential concepts of C++ preprocessing, from understanding directives to implementing macros

Preprocessor Definitions

Discover how the `#include` directive helps us include library features and split our project across multiple files.

The `#include` Directive

Explore how header files and linkers streamline C++ programming, learning to organize and link our code effectively

Header Files

The Preprocessor and the Linker

Discover additional methods and techniques to keep our data and code organised.

Learn the essentials of using namespaces to organize your code and handle large projects with ease

Namespaces

Learn about Enums and how they offer an efficient way to handle predefined values in your code

Enums

This lesson introduces the `using` keyword in C++, focusing on namespaces, enums, and type aliasing

The `using` Keyword

Namespaces and Enums

Learn how to store collections of objects, and take control of how memory is managed

Explore the fundamentals of dynamic arrays with an introduction to `std::vector`

Dynamic Arrays using `std::vector`

Learn how to manage dynamic memory using unique pointers and the concept of memory ownership

Memory Ownership and Smart Pointers

Explore advanced techniques for managing object copying and resource allocation

Copy Constructors and Operators

Learn the techniques and pitfalls of manual memory management in C++

Managing Memory Manually

Arrays and Dynamic Memory

Techniques to simplify our code, making it easier to understand and maintain

This lesson covers how we can ask the compiler to infer what types we are using through the `auto` keyword

Automatic Type Deduction using `auto`

Learn the intricacies of using `const` and how to apply it in different contexts

Constants and `const`-Correctness

This lesson provides an overview of effective commenting strategies, including Javadoc style commenting for automated documentation

Effective Comments and Javadoc

This lesson introduces the concept of Style Guides and ClangFormat, focusing on how to achieve consistency in our code

Style Guides and Automatic Code Formatting

An introduction to static analysis tools, and how they can help beginners learn faster and improve code quality

Static Analysis

Explore the fundamentals of attributes, including `[[nodiscard]]`, `[[likely]]`, and `[[deprecated]]`

Attributes

Clean Code

A collection of lessons covering a variety of topics worth learning as a beginner

This lesson covers the basics of using randomness, with practical applications

Random Number Generation

Learn the basics of the chrono library and discover how to effectively manage durations, clocks, and time points

Dates, Times and Durations

A detailed guide to string formatting using C++20's `std::format()`, and C++23's `std::print()`

String Interpolation

Learn how to overload the `<<` operator, so our custom types can stream information directly to the console using `std::cout`

Overloading the `<<` Operator

This lesson introduces system calls, and how to use them to clear the terminal

System Calls and Terminal Management

This lesson introduces the fundamentals of capturing user input, using `std::cin` and `std::getline()`

User Input in the Terminal

Unravel the fundamentals of bitwise operators and bit flags in this practical lesson

Bitwise Operators and Bit Flags

Odds and Ends

This course is designed for beginners. We'll take you from the fundamentals and lay a solid foundation for creating real-world programs and learning more advanced concepts.

Become a software engineer with C++.  Starting from the basics, we guide you step by step along the way

This course teaches the fundamentals of C++ while instilling habits used by real-world developers. You'll gain practical experience with concepts that are the foundation of all modern programming.

No previous programming experience is needed - we start from the basics.

Start your Journey

We explain every line of code we're using, so you understand exactly what is happening.

Understand Every Line of Code

Everything we create is organised and implemented using modern, professional practices.

Use Professional Best Practices

We don't just explain what we're doing, but also why. This builds transferrable skills, so you can take what you've learnt and apply them to your own projects.

Focus on Transferrable Skills

No paywalls, no ads - the course is completely free with unlimited access

Free and Unrestricted Access

We break complex concepts into manageable steps, making even advanced topics feel approachable.

Step-by-Step Learning

What You'll Learn

Comprehensive course covering advanced concepts, and how to use them on large-scale projects.

Professional C++

If you're already familiar with the basics of C++ and object oriented programming, you may want to skip to the advanced course.  It starts with a quick summary of everything we cover here.

Already Familiar with Programming?

Intro to C++ Programming

In programming, we can imagine our code being split into regions, sometimes referred to as _**scopes**_.  When we declare a variable in one region or scope, it may not be accessible to other scopes.


## Global / File Scope


We have thus far been declaring our variables at the top of our files, outside of any function body.  This scope is sometimes referred to as the _**global scope**_, also known as the _**file scope**_.


This is because, as we've seen, we've been able to freely access these variables anywhere within our file:


```c++
#include <iostream>
using namespace std;

int x{42};

void Log(){ cout << "x is " << x; }//<h>

int main(){
  Log();
  cout << "\nit's definitely " << x;//<h>
}
```


```c++
//<o>
x is 42
it's definitely 42
```


But this is not the only place we can declare variables.  For example, we can also create variables within the scope of a function, by placing it between the `{` and `}` of the function's body.


Below, we've moved our `x` variable into the scope of our `Log()` function.  As a result, it is no longer in the global scope, and is therefore no longer accessible by our `main` function.


As such, our code throws a compilation error when `main` attempts to find `x`:


```c++
#include <iostream>
using namespace std;

void Log(){
  int x{42};//<h>
  cout << "x is " << x;
}

int main(){
  Log();
  cout << "\nit's definitely " << x;//<e>
}
```


```c++
//<o>
error: 'x': undeclared identifier
```


<Aside>


### Why Would We Reduce a Variable's Scope?


When we have a tiny program with only a few variables, placing them in the global scope is reasonable.  It makes them accessible to all of our functions, which is quite useful.


However, realistic programs are much more complex, and can have thousands, millions, or even billions of variables.  Having them all in the global scope quickly becomes uncontrollable.  Even finding a unique and friendly name for a variable in a scope with a million other variables becomes a challenge.


Restricting the scope of our variables to just where they're needed is the first technique of many that can help us manage the complexity required to create larger projects.


</Aside>


## Block Scope


Block scopes are created when we have a pair of curly braces `{}` in our code.  Function bodies create a block scope, as we've seen above.


This concept isn't limited to function bodies - for example, `if` and `else` statements can also create a block scope.  Let's see an example:


```c++
#include <iostream>
using namespace std;

int main() {
  bool shouldLog{true};
  if (shouldLog) {
    string Message{"Hello World"};
  }
  cout << Message;//<e>
}
```


```c++
//<o>
error: `Message`: undeclared identifier
```


In this code, the variable `Message` is declared within the `if` statement's block. Consequently, `Message` only exists within this block and is inaccessible outside of it.


When we try to use `Message` outside of its block (here, in the `cout` statement), the compiler throws an error.  This is because `Message` is not recognized outside its defining block.


Block scopes do not need to be associated with functions or `if` statements - we can open a set of curly braces any time we want, thereby creating a new scope.


It's somewhat uncommon to do this, but it highlights the key point:


```c++
#include <iostream>
using namespace std;

int main() {
  {
    string Message{"Hello World"};
  }
  cout << Message;//<e>
}
```


```c++
//<o>
error: `Message`: undeclared identifier
```


<Aside>


### Function Parameter Scope


Function parameters are scoped to the block of the function for which they are defined.  That is, they have the same scope as if they had been variables declared within the function body.  For example, `x` and `y` have the same scope:


```c++
int Add42(int x){
  int y{42};
  return x + y;
}
```


</Aside>


## Scope Access Rules


In C++, the scope access rules govern how different parts of a program can access variables.


The key rule is: a scope can access variables from its parent scopes, but not from its child scopes.  The previous errors were all caused by code in a scope trying to access a variable in a nested, or child scope.


Previously, we've been writing code in function scopes that access variables in parent scopes (typically, the global scope).  As we've seen, that has been successful:


```c++
#include <iostream>
using namespace std;
string Message{"Hello World"};

int main(){
  // Accessing variable in parent scope
  cout << Message; //<h>
}
```


```c++
//<o>
Hello World
```


Below, we show another variation of a child scope successfully accessing a variable in a parent scope:


```c++
#include <iostream>
using namespace std;

int main(){
  bool shouldLog{true};
  string Message{"Hello World"};
  if (shouldLog) {
    // Accessing variable in parent scope
    cout << Message;//<h>
  }
}
```


```c++
//<o>
Hello World
```


Here, `Message` is declared in the `main` function's scope. The `if` statement within `main` represents a child scope, nested within the `main` function's scope.


As such, variables declared in `main` (parent scope) can be accessed in the `if` statement (child scope). 


<Quiz title="Scope Access">


<Question>


What will the following function return?


```c++
int GetInt() {
  int x{1};
  { x++; }
  return x;
}
```


<Answer>


The integer `1`


<Feedback>


Consider how block scope works in C++. Does the scope of the **`{}`** block affect the variable **`x`** outside of it?


</Feedback>


</Answer>


<Answer isCorrect>


The integer `2`


<Feedback>


Correct! This demonstrates how changes to a variable within a block scope are reflected in the variable outside the block, as long as it's the same variable.


</Feedback>


</Answer>


<Answer>


This code is invalid


<Feedback>


Review the rules of block scope and variable accessibility within and outside of **`{}`** blocks. Does this code violate any of those rules?


</Feedback>


</Answer>


</Question>


<Question>


What will the following function return?


```c++
int GetInt() {
  {
    int x{1};
    x++;
  }
  return x;
}
```


<Answer>


The integer `1`


<Feedback>


Examine where the variable **`x`** is declared and where it's being modified. How does the scope of a variable affect its accessibility?


</Feedback>


</Answer>


<Answer>


The integer `2`


<Feedback>


Think about a variable declared within a block. Is it accessible outside that block?


</Feedback>


</Answer>


<Answer isCorrect>


This code is invalid


<Feedback>


Correct! This highlights the importance of the scope in which a variable is declared. A variable declared within a block is not inherently accessible outside that block.


</Feedback>


</Answer>


</Question>


</Quiz>


## Shadowed Variables / Name Hiding


_**Shadowing**_ or _**name hiding**_ occurs when multiple variables with the same name are accessible at once.  This is the result of a variable in an inner scope using a name of a variable in one of its parent scopes.


The variable in the inner scope "shadows" the variable in the outer scope, making the outer variable difficult to access within the inner scope. Here's an example to demonstrate this concept:


```c++
#include <iostream>
using namespace std;

int main(){
  int x{1};
  {
    // This 'x' shadows the outer 'x'
    int x{2};
    cout << "Inner x: " << x; // Outputs 2
  }
  cout << "\nOuter x: " << x; // Outputs 1
}
```


```c++
//<o>
Inner x: 2
Outer x: 1
```


In this example, there are two variables named `x`. The `x` inside the block is separate and shadows the `x` declared in the `main` function.


Within the block, any reference to `x` refers to the inner `x` (with value 2), not the outer `x` (with value 1). When the block ends, the inner `x` goes out of scope, and the outer `x` becomes accessible again.


Shadowing is typically something we want to avoid, as it can lead to confusion and bugs.  However, it's still important to understand what's going on here, so we can ensure we're accessing the correct variables.


<Quiz title="Variable Shadowing">


<Question>


What will the following function return?


```c++
int GetInt() {
  int x{1};
  {
    int x{2};
  }
  return x;
}
```


<Answer isCorrect>


The integer `1`


<Feedback>


Correct! This illustrates the concept of variable shadowing. The `x` inside the block is a different variable from the `x` outside it, despite having the same name.


The `return` statement does not have access to the `x` declared in the child scope, which has a value of `2`.  But it does have access to the `x` declared in the function scope, which has a value of `1`.


</Feedback>


</Answer>


<Answer>


The integer `2`


<Feedback>


Consider the concept of variable shadowing in C++. When the same variable name is used within a nested scope, does it refer to the same variable or a new one?


</Feedback>


</Answer>


<Answer>


This code is invalid


<Feedback>


Review the rules about variable declaration and scope. While there are two variables named **`x`**, the code is valid because each **`x`** is in a different scope.


</Feedback>


</Answer>


</Question>


</Quiz>


<Aside>


### Preview: Designing with Scopes


Right now, the rules and complexities around scopes might seem a bit much, especially given how simple our programs are.


As our projects become larger, we'll come to appreciate and embrace scoping to make our program more manageable.


We'll soon learn to use the scope resolution operator and namespaces, which help access and group code across different scopes, helping us with this task.


</Aside>


## Summary


In this lesson on scope in C++, you've learned several key concepts:

- **Global/File Scope**: Variables declared outside any function have global scope and can be accessed anywhere within the file.
- **Block Scope**: Variables declared within a set of **`{}`** are only accessible within those braces.
- **Scope Access Rules**: A scope can access variables from its parent scopes but not from its child scopes.
- **Shadowed Variables/Name Hiding**: When two variables with the same name exist in different scopes, the one in the inner scope shadows the one in the outer scope.

<Preview>


### Forward Declaration


In the next lesson, we will introduce forward declaration, focusing on its application in functions.


Forward declaration allows you to inform the compiler about the existence of an entity (like a function) before you provide its complete definition.


This technique can help in organizing and structuring your code more effectively. We'll explore:

- What is a forward declaration
- What is a circular dependency, and how can forward declarations solve them
- Practical examples demonstrating forward declaration with functions.

</Preview>

Added section to explain why reducing scope is desirable

Scope of Variables in C++

Scope - C++ Documentation

Understanding Scope and Scope Resolution in C++

C++ Variable Scope

{CPP}Beginner-friendly guide to C++ scopes: Discover how to manage variable visibility

Scope

Understanding the Basics

Practical Applications

Common Mistakes

Next Steps

Additional Resources

Assessment Preparation

Intro to C++ Programming