Execute a C++ program using g++ CLI

1 minute read

Choice of compiler and editor

I think vs-code is a good place to start. My setup is wsl2/ubuntu/g++ on windows machine and clang on mac.

First Program

Below are three versions of the hello world program.

not using namespace keyword.

#include <iostream>

// first program
int main()
{
  std::cout << "hello, world!" << std::endl;
  return 0;
}

using namespace std; scope.

#include <iostream>

using namespace std;

// first program
int main()
{
    cout << "hello, world!" << endl;
    return 0;
}

using namespace restricted to the keyword scope.

#include <iostream>

using std::cout;
using std::endl;

/* multi line comment example:
 * first program
*/
int main()
{
    cout << "hello, world!" << endl;
    return 0;
}

Program Structure

  • # in #include <iostream> is a preprocessor directive and it’s processed before actual compilation. The purpose of the directive is to prepare the program for compilation.
  • include keyword is used to import libraries.
    • standard library names are enclosed in <>
    • user-defined library names are enclosed in ""
    • the line is not terminated with ;
  • every c++ program has one main function which serves as an entry point.
  • single line comments // this is a one line comment
  • multi line comments 
    /*
this is a multi-line comment
1 ...
2 ...
*/
  • :: is a scope resolution operator.
  • cout - standard output stream
  • << - insertion operator for output streams
  • cin - standard input stream
  • >> - extraction operator for input streams

How to execute C++ program

  • Compile the program: g++ main.cpp -o hello
  • Execute the program: ./hello

References