What Is C++?
Imagine you are building Rocket Run, a small arcade game: a rocket dodges asteroids, collects coins and tries to beat a high score. It must redraw the screen dozens of times a second on anything from a gaming PC to a cheap laptop. That kind of job is exactly what C++ was designed for, and Rocket Run will be our example for the whole course.
The rule
C++ is translated to machine code before it runs, and checked on the way.
Three ideas are packed into that line.
- Compiled. A program called a compiler reads your source file and translates it into machine code, the instructions your processor executes directly. The finished program runs without the compiler.
- Checked. Every variable has a type fixed in the source, such as
intfor whole numbers. The compiler checks all of them before producing anything. This is called static typing. - General purpose, many styles. You can write plain step-by-step functions, group data and behaviour into classes, or write generic code with templates. C++ lets you mix all three.
Here is the smallest piece of Rocket Run:
#include <iostream>
int main() {
int lives = 3;
std::cout << "Lives: " << lives << '\n';
}A little history helps the names make sense. Bjarne Stroustrup started the language at Bell Labs in 1979 as "C with Classes", and it was renamed C++ in 1983 (++ means "add one" in C). Today an ISO committee publishes a new standard every three years: C++11, 14, 17, 20 and 23. This course uses C++17 and C++20.
The shortcut
When someone asks "what happens to my C++ code?", picture a factory line: source → compiler → executable → run. Anything wrong with types is caught at the compiler stage, long before the run stage.
Write the source
You type the code above into a text file called
rocket.cpp. It is only text; nothing can run it yet.
A common mistake is to think C++ reads your file line by line as it runs, the way a Python interpreter does. It does not: by the time anything runs, the whole file has already been translated.
Drills
Answer fast — trust the rule.
What does the compiler produce from rocket.cpp?
When is the mistake in int lives = "three"; reported?
Which programming styles does C++ support?
Who decides what counts as correct C++?
Remember
- C++ is translated to machine code before it runs, and checked on the way.
- Picture the line: source → compiler → executable → run.
- Trap: C++ is not interpreted line by line; type errors stop the build, not the game.