A C++ program is basically a collection of statements and expressions, usually organized into functions and classes. The best way to learn a programming language is by writing programs. The first program you typically see is a "Hello World" program. This simple program prints Hello World to your screen. This is a great way just to test you are able to compile, link, and execute your source code.

// my first program in C++
#include <iostream>

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

Line 1:
The first line of this program, you'll notice these two slash marks, followed by some text. This how your can write a comment in C++. Comments are ignored by the compiler.

// my first program in C++

or you can write a comment like this:

/*
You can also write comments between these tags if you want them to span multiple lines.
*/

Programmers use them to include short explanations or observations concerning the code or program.

Line 2:
Lines beginning with a hash sign (#) are directives read and interpreted by what is known as the preprocessor. They are special lines interpreted before the compilation of the program itself begins. In this case, the directive #include <iostream>, instructs the preprocessor to include a section of standard C++ code, known as header iostream, that allows to perform standard input and output operations

#include <iostream>

This tells the preprocessor to take that file and include it in this source code file as if I had typed it. It's hundreds of lines of code, so I don't want to type it.

Line 3:
Blank lines have no effect on a program. They simply improve readability of the code.

Line 4:
The function named main is a special function in all C++ programs; it is the function called when the program is run. This is the main entry point for any C++ program. The execution of all C++ programs begins with the main function, regardless of where the function is actually located within the code.

int main()

This line initiates the declaration of a function. Essentially, a function is a group of code statements which are given a name: in this case, this gives the name "main" to the group of code statements that follow.

Lines 5 and 7: { and } The open brace ({) at line 5 indicates the beginning of main's function definition, and the closing brace (}) at line 7, indicates its end. Everything between these braces is the function's body that defines what happens when main is called. All functions use braces to indicate the beginning and end of their definitions.

Line 6:
This line is a C++ statement. Statements are executed in order.

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

This statement has three parts:

std::cout, which identifies the standard character output device (usually, this is the computer screen).
the insertion operator (<<), which indicates that what follows is inserted into std::cout.
a sentence within quotes ("Hello world!"), is the content inserted into the standard output.

Notice that the statement ends with a semicolon (;). This character marks the end of the statement.

Note: if you wanted to skip a line after Hello World you could have done either of these two methods:

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

This is the Anatomy of a basic C++ program- Hello World.