Question

Write a complete \(C++\) program that writes the phrase Hello world to the screen. The program does nothing else.

Short answer

Question: State the purpose of including the iostream library in a C++ program. Answer: The purpose of including the iostream library in a C++ program is to enable input and output operations, such as using 'cout' to display text on the screen.

Step-by-step solution

Include necessary libraries

To begin, include the necessary library (iostream) in your program. The 'iostream' library is used for input and output operations in a C++ program, and we'll be using 'cout' from this library to display our text. ```cpp #include ```

Declare the main function

Declare the main function, which is the entry point of our program. All C++ programs must have a main function. The function returns an integer (int), and takes no arguments/parameters. ```cpp int main() { } ```

Add 'cout' statement inside the main function

Inside the main function, use the 'cout' statement along with the '<<' operator to output the "Hello world" text to the screen. ```cpp int main() { std::cout << "Hello world"; } ```

Add a return statement and a newline character

It is good practice to end the main function with a return statement since the function is declared with a return type of 'int'. Additionally, to make the output look cleaner, it's recommended to add a newline character at the end of the "Hello world" text by using 'endl'. ```cpp int main() { std::cout << "Hello world" << std::endl; return 0; } ```

Final C++ program

Combine all the steps to create the final C++ program. The program writes the phrase "Hello world" to the screen and does nothing else. ```cpp #include int main() { std::cout << "Hello world" << std::endl; return 0; } ```