Use the GNU C++ compiler g++: g++ hello.cpp produces a.out, or g++ -o hello hello.cpp to name the output.

C++ source files use the .cpp extension and are built with g++, the C++ front-end of the GNU Compiler Collection (the C front-end is gcc).

# Creates a.out
$ g++ hello.cpp
# Creates 'hello' executable
$ g++ -o hello hello.cpp
# Run it
$ ./hello

Key differences from C:

• Use g++ instead of gcc (so the C++ standard library links automatically)
• File extension is .cpp (not .c)

In a Makefile:

CXX=g++
CXXFLAGS=-Wall -O2 -std=c++0x

Tip: CXX is the conventional Makefile variable for the C++ compiler (mirroring CC for C), and CXXFLAGS holds its flags. -std= picks the language standard. c++0x was the working name for what became C++11; modern code uses concrete names like c++17 or c++20.

Include <iostream>, then write cout << "Hello, world!" << endl; inside main().

#include <iostream>
using namespace std;

int main(void) {
    cout << "Hello, world!" << endl;
    return 0;
}

Key C++ elements:

• #include <iostream> — C++ stream I/O library (not C's stdio.h)
• using namespace std; — lets you write cout instead of std::cout
• cout << — sends text to the output stream (the C++ replacement for printf)
• endl — writes a newline and flushes the buffer (or use "\n" for just the newline)

Compile and run:

$ g++ -o hello hello.cpp
$ ./hello
Hello, world!