A C++ program has a very specific structure in terms of how the code is written. There are some key elements that you use in all your C++ programs.

Here, we have a program called hello.cpp. It is a classic first program!

// This program outputs the message "Hello World!" to the monitor

#include <iostream>

int main()
{

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

}

This program writes the phrase "Hello, World!" to your terminal.

C++ is a case sensitive language. Case sensitivity means that your keywords and variable declarations must match the case. For example, the C++ keyword for outputting is cout. If you were to type Cout or COUT, the compiler would not know that your intention was to use the keyword cout.

Note: Don't be intimidated by all the new information. You'll learn about all of these things (and a whole lot more)!


Let's go over this hello.cpp program line by line:

  • // This program outputs the message "Hello World!" to the monitor
    
    This is a single-line comment that documents this code. The compiler will ignore everything after // to the end of the line.
  • #include <iostream>
    
    This is known as a pre-processor directive. It instructs the compiler to locate the file that contains code for a library known as iostream. This library contains code that allows for input and output, such as displaying data in the terminal window, or reading input from your keyboard.
  • int main() 
    { 
      // Statements
    }
    
    Every C++ program must have a function called main(). A function is basically a sequence of instructions for the computer to execute. This main() function houses all of our instructions for our program. This is where we will be writing our code.
  • std::cout << "Hello World!\n";
    
    This code uses a method known as cout (pronounced "see out") to send the text "Hello World!" to the terminal for output.

C++ programs permits judicious use of white space (tabs, spaces, new lines) to create code that is easier to read. The compiler completely ignores the white space, with a small exception concerning if statements that will be covered later. It is highly recommended that you make use of white space to indent and separate lines of code to aid in readability of your source code files.


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