Exercise "hello"

Install csharp-mono on your system, and build a hello-world program – a program that outputs "Hello, World!".

Hints:

Install mono with the command
```
sudo apt install mono-mcs
```
MacOS users might need to install mono from the mono-poject [mono-project.com].
Create a folder for the exercise, let's say "~/repos/ppnm/exercises/hello":
```
mkdir -p ~/repos/ppnm/exercises/hello
```
Go to your directory (remember to use completion feature of your shell !):
```
cd ~/repos/ppnm/exercises/hello
```

Create a Makefile with the following content (mind the tabulators!) (and you can omit comments):

out.txt : hello.exe              # out.txt depends on hello.exe
	mono hello.exe > out.txt # run hello.exe, send output to out.txt

hello.exe : hello.cs             # hello.exe depends on hello.cs
	mcs hello.cs             # compile hello.cs into hello.exe

clean:                           # a phoney target, no dependencies
	rm -f out.txt hello.exe  # remove secondary files

Create a file hello.cs with the following content

class hello{
	static void Main(){
		System.Console.Write("hello\n");
	}
}

Run make and debug.

Extra hints:

For nano users: you can indicate the invisible tabulator-signs with a color by adding the following lines to your ~/.nanorc,
```
syntax "makefile" "[Mm]akefile"
color white,magenta "	"
```
where the character in between the quotation marks in the second line should be the tabulator sign and where the colors are free for you to choose.
If you use GNU make version 3.82+ and you don't like your recipies to start with tabulator-sign, you can do .RECIPEPREFIX := ;.