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Introduction

Programming is the act of giving a computer step-by-step instructions to follow. You write the steps in a language the computer can be made to understand (in this course, C++), and a tool called a compiler translates them into something the machine can actually run.

This book is your companion for AIS1003. It will not replace practice. Most of what you learn about programming comes from writing code, making mistakes, and figuring out what went wrong. The chapters here are a reference and a starting point; the keyboard is where the real work happens.

What is a program?

A program is a sequence of operations the computer carries out in order. At its smallest:

#include <iostream>

int main() {
    std::cout << "Hello, world!" << "\n";
    return 0;
}

▶ Run on Compiler Explorer

A few lines, but every part matters:

  • #include <iostream> pulls in the part of the standard library you need to print to the screen.
  • int main() declares the entry point. Every C++ program starts here.
  • The line ending in ; is one statement, one thing for the computer to do.
  • return 0 signals to the operating system that the program finished successfully.

When you run this, the compiler reads the source code, checks it for errors, translates it into instructions for your CPU, and produces an executable file. You then run that file, and the text appears.

A short history

Computers only understand one thing: machine code, long strings of 1s and 0s that correspond to the most primitive operations the processor can perform — add these two numbers, move this value, jump to that instruction. The first programmers wrote those numbers by hand. It worked, but it was slow, unreadable, and tied to one specific machine.

The history of programming languages is the story of climbing away from those 1s and 0s toward something a human can read and reason about, while a tool handles the translation back down to the machine.

  • Machine code (1940s). Raw numeric instructions. Fast for the computer, miserable for the human.
  • Assembly (1950s). Short mnemonics like ADD and MOV stand in for the numbers. Easier to read, but still one line per machine instruction and still tied to one kind of processor.
  • High-level languages (late 1950s onward). FORTRAN, and many after it, let you write something closer to human ideas — x = a + b instead of a sequence of register operations. A compiler translates the whole program down to machine code, so you could write it once and, in principle, run it on different machines.
  • C (1972). Dennis Ritchie at Bell Labs created C to write the Unix operating system. It was high-level enough to be readable, yet stayed close to the hardware, so it produced fast, compact programs. C became one of the most influential languages ever written: its syntax is the ancestor of C++, Java, C#, and JavaScript. The { }, the ;, and the int main() you saw above all come from C.

From C to C++

In 1979 Bjarne Stroustrup, also at Bell Labs, wanted C's speed and low-level control plus a way to organise large programs around classes — the object-oriented idea, borrowed from an older language called Simula. He began by extending C and called it "C with Classes." In 1983 it was renamed C++: ++ is the C operator that means "add one," so the name is a small joke — one more than C.

C++ became an international standard in 1998 (C++98), so that every compiler would agree on what the language meant. Then it sat mostly still for over a decade.

The turning point was C++11. It modernised the language so thoroughly that people now speak of "old C++" and "modern C++" almost as different languages. Modern C++ added features that make the language safer and far less tedious to write — you will meet them throughout this book. Since C++11, a new standard has arrived roughly every three years:

Standard Year Note
C++98 / C++03 1998 / 2003 The first standardised C++.
C++11 2011 The leap to "modern C++."
C++14 / C++17 2014 / 2017 Steady refinements.
C++20 2020 What this course teaches.
C++23 2023 The current latest.

You do not need to memorise this. The takeaway is simple: C++ is old enough to run almost everything, and modern C++ is new enough to be pleasant to write — as long as you stick to the modern style this book teaches.

Why C++?

You will hear that C++ is a "difficult" language. There is truth to that: it gives you direct control over the machine, and with that control comes more ways to make mistakes than in something like Python. But it is the right tool for what automation engineers actually do:

  • Embedded systems and robotics. Arduino, PlatformIO, ROS, industrial controllers; almost all run code written in C++ or C.
  • High-performance numerical work. Control loops, signal processing, simulations.
  • Game engines and graphics. Unreal, large parts of Unity's runtime.
  • Operating systems and drivers. Code that talks to hardware directly.

Compiled, statically typed

Two properties of C++ shape how you write it.

Compiled. Your source code is translated to machine code once, ahead of time, by the compiler. The program does not run until compilation succeeds. This means many bugs (typos, type mismatches, missing semicolons) are caught before the program ever executes. Compare this to Python, where a misspelled name or a type mismatch is not discovered until the program actually runs that line — so a mistake sitting on line 200 stays hidden until execution reaches it.

Statically typed. Every variable has a fixed type that you declare up front:

int age = 25;         // age holds whole numbers, forever
double price = 19.99; // price holds decimals, forever

You cannot later put a string in age. The compiler enforces this. Static typing means more typing for you, but in exchange the compiler catches a large class of bugs automatically: you cannot accidentally pass a string where a number is expected.

A short list of consequences you will run into:

Property What it means for you
Compiled You must rebuild before you can test a change. Read compiler errors carefully.
Platform-specific The compiler emits machine code for one OS and CPU. A Windows build won't run on Linux, and the same source isn't always guaranteed to compile on both — see Portability.
Statically typed You declare every variable with a type. Mismatches are compile-time errors, not runtime crashes.
No garbage collector You manage when memory is freed (later chapters cover the modern, painless way).
Undefined behaviour exists The language has corners where "anything could happen." We will name them as they appear.

Object-oriented programming

OOP is the way C++ is normally written. Instead of one long list of instructions, you organise your code around objects: bundles of data together with the operations that work on that data.

A Motor object might hold its current speed and its maximum speed, and provide operations like setSpeed(), stop(), and getStatus(). The rest of your program treats the motor as a single unit and does not need to know how the internals work.

The key terms you will meet:

Term Meaning
Class The blueprint. Describes what data an object holds and what it can do.
Object An actual instance of a class; a specific motor, sensor, or controller in memory.
Member A piece of data or a function that belongs to a class.
Encapsulation Hiding the inside of a class behind a clean interface, so outside code cannot break invariants.
Inheritance Building a new class on top of an existing one.
Polymorphism Treating different concrete types through a common interface.

We will not write a class today. Chapter 4 covers them properly. For now, keep these words in the back of your mind.

How to use this book

Read each chapter, then write code. Type the examples by hand rather than copy-pasting; the typos you make are how you learn what the compiler complains about. When you get an error you do not understand, see the Reading Compiler Errors reference, then search the exact error text. Almost every compiler error has been asked about on Stack Overflow.

If you have written some Python before — many of you have — Coming from Python maps what carries over and the "false friends" that will trip you up.

AI assistants will happily write C++ for you. Read Using AI for Coding before relying on them. The short version: they are excellent tools and treacherous teachers, and using them well requires a few specific habits.

When this book gives a recommendation, it is the one you should follow unless you have a specific reason not to. C++ has many ways to do most things, and a beginner who tries to learn all of them ends up confused. Learn the one good way first.

Up next: Basic Structure breaks down a complete C++ program piece by piece. If you have not yet installed CLion, see Getting Started first.