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Hello everyone and welcome to this 
short video series about GROOPS.  

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My name is Sebastian Strasser and I'm going 
to show you the basic features of GROOPS.  

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So this first video will be a short overview about 
GROOPS, what it is, how to use it, how to use the  

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graphical user interface and so on. So let's 
start here on GitHub. This is our repository,  

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where you can download GROOPS and this is also the 
right place to ask any questions or submit any bug  

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reports and so on. So, first of all, you have 
to install GROOPS. We have an installation page  

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with instructions for Microsoft Windows and 
also several Linux distributions. So here  

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you can just follow these steps to install 
GROOPS on your operating system of choice.  

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There's also a link to our documentation, 
which we will use later in this series,  

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where you can find information on basic 
features but also cookbooks to perform  

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specific tasks and also a description of all 
the classes and programs you find in GROOPS.  

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So after you have installed GROOPS, I'll show 
you a quick overview of what is GROOPS. So GROOPS  

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has both a command line application, 
which is GROOPS itself, let's call it,  

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and we have a graphical user interface. So all 
the logic is part of the command line application  

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and with the graphical user interface you just 
create so-called config files, which tell GROOPS,  

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which tell the command line application what you 
do. So from the graphical user interface you can  

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also directly call the command line application 
and run a GROOPS script. And how does the user  

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interface know which programs exist, what settings 
exist and so on. This is done by an XML schema  

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file. So the GROOPS command line application 
can create a schema file – if you've downloaded  

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GROOPS from GitHub you already have this 
file – and the GUI then parses this file  

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to know which programs there are 
and which settings there exist.  

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Okay, so let's start with the command line 
part. So if you have installed GROOPS correctly  

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you can just call GROOPS in the command 
line by entering "groops" or "groops.exe"  

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if you're on Windows. And this is just a help 
text from GROOPS, you can see there are several  

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optional arguments and the last argument is a 
config file. You can pass one or more config files  

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to run a GROOPS program. For example, I can type 
"groops ..." – I have an example script prepared  

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which is "01groopsExample.xml" – and if I run 
this you can see this script just simulates a  

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basic orbit and that's it. So it goes by 
super quickly. So, yeah that's the basic  

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principle of GROOPS. It's just a command line 
application. However, as I mentioned earlier,  

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there's also the graphical user interface, which 
looks like this. This will be your main interface  

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for GROOPS because this will be the place 
where you usually create scripts, so you  

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create the scripts which tell GROOPS what to do. 
I have here open my example script I just ran.  

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On the left we have a sidebar, which shows all 
the open files. There's also a list of programs,  

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an undo stack, which I will mention later, and 
you have a menu, of course. There are several  

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features. When you first start the graphically 
user interface you will probably be prompted to  

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set up some default paths and files. So this menu 
will show up. Here you have to set the path to the  

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schema file, which i mentioned earlier, and which 
is usually located in your GROOPS directory. You  

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can set a working directory, which is just the 
base directory where all your scripts start,  

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but of course you can use different directories 
when you save a script. And also you have to set  

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the documentation directory. This is like this 
part, so it's a subfolder "docs/html". Another  

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feature you can use is a template file. You can 
just use any GROOPS script as a template file.  

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For example, here I have my "groopsTemplate.xml" 
which is this file here. And this template file,  

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in this case, only contains global variables. 
You can imagine global variables just as global  

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variables in any programming language. And here 
you could also add some programs. The nice thing  

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about the GROOPS template is I can set up any 
variables, for example, a very important variable  

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is "groopsDataDir", which is used as a default 
variable in several paths of our programs. Here  

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you can set the path to the GROOPS data directory 
you have hopefully downloaded from the FTP server.  

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And you can also create any other variables. If 
you have set this template file in "Settings",  

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whenever you create a new script file these 
variables will be auto-generated, so everything  

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which is part of the template file will exist also 
in this file. So this is very convenient to set  

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up some basic global variables you always need. 
But let's go back to the script we just ran. It  

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is a very basic script, there is only one 
program, which is called "SimulateOrbit".  

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It has an output file. It has several 
input files. You define a time series,  

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sampling and so on. You can set up several forces. 
So here you basically just tell the program  

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what to do and which settings you want to use. 
I will go into these settings later in the next  

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video, this is just an overview of how to use it. 
For example, you could also add another program,  

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select any program you want; or you can change 
settings; you can add forces and so on. So this is  

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pretty straightforward and easy to use. 
This file, as you can see, is an XML file,  

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so if I look at this file you can see it's just 
the program we just saw – "SimulateOrbit" –  

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it has the output file, it has the time series 
and so on. It's just encoded as an XML file.

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Okay, and if you want to run this program – 
let's head to the "Undo Stack", where we can just  

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undo or redo all our changes. Let's go back to the 
initial state of the file. And if I now want to  

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run this file – earlier I showed you you can do 
it over the command line – but you can also hit  

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the green triangle button and hit run and also a 
command line window will open and run the script.  

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Okay, and another important feature of GROOPS 
is a Help feature. So you can select any program  

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and hit F1 and it will open the documentation 
in the browser, if you set the path  

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correctly. And here you have the documentation 
of the program "SimulateOrbit". You can see  

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basic text, what it does, and also a 
description of all the settings you can use.  

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Okay, that's everything I wanted to show 
you in this first video. In our next video,  

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we will create a basic, easy script, so you 
can see the process of creating a script.  

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Thanks for watching and see you in the next video!