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Hello World

Compile Command

Using GNU, the compilation command is g++ followed by the file name. Here, the name of the source file is hello.cpp.

g++ hello.cpp

Execute Command

The execution command is ./ followed by the file name. Here, the name of the executable file is a.out.

./a.out

Single-line Comments

Single-line comments are created using two consecutive forward slashes. The compiler ignores any text after // on the same line.

// This line will denote a comment in C++

Multi-line Comments

Multi-line comments are created using /* to begin the comment, and */ to end the comment. The compiler ignores any text in between.

/* 
This is all commented out.
None of it is going to run!
*/

Program Structure

The program runs line by line, from top to bottom:

  • The first line instructs the compiler to locate the file that contains a library called iostream. This library contains code that allows for input and output.
  • The main() function houses all the instructions for the program.
#include <iostream>


int main() {


  std::cout << "1\n";
  std::cout << "2\n";
  std::cout << "3\n";


}

Basic Output

std::cout is the “character output stream” and it is used to write to the standard output. It is followed by the symbols << and the value to be displayed.

std::cout << "Hello World!\n";

New Line

The escape sequence \n (backward slash and the letter n) generates a new line in a text string.

std::cout << "Hello\n";
std::cout << "Hello again\n";
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