Our computer's CPU only understand commands given to it as binary codes - strings of 1's and 0's, like this: Early programmers had to write their software using this machine code, though over time programming languages evolved. When we write source code these days, we write in a human-made, somewhat human-readable text, with specific grammars and rules to it. These source code files are plaintext - they're just simple text that can be opened in a text editor. We will be using VS Code as the editor where we will write our C++ source code.

Files on a computer use an extention to identify what kind of file it is, such as a .jpg for jpeg format images, .mp3 for audio files, .html for website layouts. At minimum, a C++ program requires one file - a .cpp source file. Usually programs are bigger and contain multiple files, like .h header files as well as other .cpp source files. The file that contains the program starting point is usually named main.cpp, though this name is not required.

The bare-minimum C++ program looks like this:

int main()
{
  // Code goes here
  return 0;
}

Every C++ program begins at a main() function.

For now you can take this code for granted but you will understand it more as the class continues. But, some basic info:

• The int main() is the function that starts our program.
• The contents of the program must be between the opening curly brace { and the closing curly brace }. This region is known as main()'s codeblock. We will see more codeblocks (with { }) later in the class.
• The return 0; is where the program ends. 0 is returned for 0 errors.
• Code we add will go after the { and before the return 0;.

Additionally, C++ is case sensitive, so capitalization matters. Make sure you write main() in all lower case - Main() and MAIN() won't work!

Remember that your computer expects to read binary 1010101010, and does not understand English or other human languages. When we're ready to run our C++ program, we need to run it through a program called a compiler.

A compiler goes through your source code, generating binary code based on what you wrote. The end result is an executable file, also known as a binary file. This is the type of program where, if you double-click it on your computer, it will run.

The compiler program we are using in class is called g++ (or MinGW, which is a Windows port of g++). When we're ready to test out our code, we can open up a terminal in VS Code and enter the command:

g++ main.cpp

We're telling the g++ compiler program to convert our main.cpp source code file into an executable. By default, it will either generate a.exe (on Windows) or a.out (on Linux/Mac), but we can always rename our program, or we can tell g++ what to name our program in the same step:

g++ main.cpp -o MyProgram.exe

Once we're ready to run our program, we would then launch it from the terminal like this:

./MyProgram.exe

Though at the moment, this program does nothing except exit! :