C# standard explanation

Hi. I am Chris. It is first posting. I do upload about C#.
C# is OOP(Object-Oriented Programming). So, C# use the function. I am used VSC(Visual Studio Community). You can install VSC go to "https://www.visualstudio.com/vs/community/"
You can coding below source code

Using System

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World");
            Console.Read();
        }
    }
}

1. It is about Using System explaining below System is located in mscorlib.dll file.
So, If a compiler case It load about System in mscorlib.dll.
mscorlib.dll is located in C drive at windows/Microsoft.NET/Framework/V.4.0.30319
Do you want to see System source code?
You reference at website https://referencesource.microsoft.com/

2. It is about namespace HelloWorld explaining below namespace is biggest mass.
class belong to namespace. namespace name is not overlap.
But class possible to overlap below namespace.

3. It is about Console.WriteLine explaining below Console. is class. WriteLine is method. Console method is located in mscorlib.dll in namespace System in class Console. There are various on WriteLine method. This is example above using method.

public static void WriteLine(char value)
{
            Out.WriteLine(value);
}

I studied until here. Programming is made function and function. small function and big function. I just think simply to be used from small function to big function.