include

int main() { std::cout << "Hello World!"; return 0; }

Explanation: 1. The line "#include " includes the input-output stream library in the C++ program. This library provides functions to perform input and output operations, such as printing to the console.

1. The "int main()" line is the starting point of the C++ program. It declares the main function, which is the entry point for the program execution.

2. The opening brace "{" indicates the beginning of the main function.

3. The line "std::cout << "Hello World!";" is responsible for printing the message "Hello World!" to the console.

4. The "std::cout" is an object that represents the standard output stream, which is usually the console. The "<<" operator is used to insert the message "Hello World!" into the output stream.

5. The semicolon ";" at the end of the line marks the end of the statement.

6. The "return 0;" line is used to exit the main function and return a value of 0 to the operating system. In C++, returning 0 from the main function usually indicates successful program execution.

7. The closing brace "}" indicates the end of the main function.