What Is C++ and Why Compile?

C++ is a compiled language: before your program runs, a program called the compiler translates your human-readable source code (.cpp files) into machine code your CPU executes directly. That translation step is what makes C++ fast — and it is also why C++ catches certain mistakes before the program ever runs.

The workflow you will repeat thousands of times

edit code  →  compile  →  run  →  (read output or errors)  →  repeat

Compare that with Python, where the interpreter reads your source directly. In C++, two different tools answer two different questions:

• The compiler (g++) turns source into an executable and refuses to build code it cannot understand. A compiler error means "this is not valid C++".
• The runtime is your program actually executing. A runtime error (a crash) means valid C++ did something dangerous, like dividing by zero or reading past the end of a collection.

Why learn C++ in 2026?

• It runs everywhere performance matters: games, browsers, databases, operating systems, embedded devices, trading systems.
• It teaches you what the machine is really doing: memory, lifetime, and cost. That knowledge makes you better at every language.
• Modern C++ (C++20 is this course's baseline) is a much safer, more expressive language than the C++ of the 1990s. This course teaches the modern language — not "C with classes".

What "statically typed" buys you

Every variable's type is known at compile time:

int score = 100;        // the compiler knows this is a whole number
double price = 9.99;    // ...and this is a decimal

If you later write score = "high"; the compiler stops you with an error — in Python the same mistake would explode at runtime, possibly in production, possibly on a Tuesday night. Types are a feature, and you will learn to lean on them.

A note on the platform

In this course you write C++ in the browser editor and the platform compiles and runs it in an isolated sandbox using GCC. The graded programs follow one convention you will meet in the next lesson: your code is compiled as a single file, and interactive keyboard input is not part of grading — challenges check what your functions return and what your program prints.

Coming up: your first program, and the strange little word main.