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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.


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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