Your First Program

Enemy 1 of 5

What a C++ program looks like

Every C++ program needs a starting point, and that starting point is always a function named main. When you click Run, the computer doesn't read your file top to bottom like a story. It jumps straight to main and begins executing the instructions inside its curly braces { }. Everything the program actually does lives inside that block.

Before main, you'll usually see one or more #include lines. These pull in pieces of the C++ standard library so you can use tools that aren't built into the bare language. In the example below, #include <iostream> brings in input/output support. Without it, cout (which prints to the screen) wouldn't exist at all. Think of #include as saying "I'm going to need this toolbox, please hand it to me before I start."

The line using namespace std; tells the compiler it's fine to write cout instead of the fully-qualified std::cout. It's a convenience that most beginner (and plenty of professional) programs use to keep code shorter and easier to read.