# Introduction

**What**

This is an introductory "hands-on" tutorial on [ROOT](https://root.cern/),
a C++ and Python-based data-analysis software toolkit developed
at [CERN](https://cern.ch/), a high-energy particle-physics accelerator research
facility on the French-Swiss border. 

**Who**

The target audience for this workshop are undergraduate students in
the sciences who are looking for summer research experience; for
example, those in the US [National Science
Foundation](https://www.nsf.gov/)'s [Research Experience for
Undergraduates (REU)](https://www.nsf.gov/crssprgm/reu/) program. 

Many parts of this tutorial are optional or are advanced exercises. No
one expects you to get through all these pages before you start your
physics work for the summer. Much of the material, especially from
{ref}`intermediate topics` on, is intended to use as a reference if
you continue to use ROOT in the future.

I tried to "aim low" in terms of expectations on the required
knowledge of computing, math, and science.  Anyone with access to a
computer with ROOT installed, or with a laptop on which they're
willing to put in the effort to {ref}`install ROOT <installing>`, should be able to work
their way through this material.

**Where**

This workshop is taught at [Nevis Labs](https://nevis.columbia.edu/). I've provided
resources for those with login access to the [Nevis
particle-physics Linux
cluster](https://twiki.nevis.columbia.edu/twiki/bin/view/Main/LinuxCluster),
such as a [JupyterHub
server](https://twiki.nevis.columbia.edu/twiki/bin/view/Main/IPython)
with ROOT pre-installed. Therefore, some of the set-up instructions
are Nevis-specific.

I've tried to provide alternative instructions for anyone to be able
to take this tutorial, even if they're not at Nevis. There are several
ways to {ref}`install ROOT <installing>`, and any
[files](https://www.nevis.columbia.edu/~seligman/root-class/files/)
can be easily copied.

In addition to the web site you're reading now, 
you can find this tutorial in PDF format, along with related
material, on my [ROOT
Tutorial](https://www.nevis.columbia.edu/~seligman/root-class/) page. 

**How**

The lessons have time estimates at the top. These are only rough
estimates. Don't be concerned about time. The important thing is for
you to learn something, not to punch a time clock.

If you're programming for the first time, then the exercises are
challenging. Getting to all but the last exercise (the
stand-alone program) in either {ref}`cpath` or {ref}`pythonpath`
is a respectable achievement on its own. 

On the other hand, if the class seems too easy, just keep going. I
gradually ramp up the difficulty. The lessons do not stay at the level
of "ROOT does what physicists do."

**When**

This tutorial started as a one-day class I taught at [Columbia
University](https://www.columbia.edu/)'s [Nevis
Laboratories](https://nevis.columbia.edu/) in 2001. Over the years,
I've {ref}`revised <version history>` it as different versions of ROOT
came out, and in response to comments received from the students.

**Why**

*Disclaimer*

Although the developers of ROOT have always been ready to 
answer my questions, they have had no direct input on the contents of this
tutorial. 

In particular, they had no say in the flippant, humorous, and
occasionally sarcastic tone in which I've decided to present the
material. This includes the over-use of smart-aleck footnotes and
[xkcd](https://xkcd.com) cartoons.[^xkcd-tip]

[^xkcd-tip]: I've included a link in each figure caption of any xkcd
    cartoon I use. However, I don't include the hover-text, which is
    occasionally funnier than the cartoon itself. For extra added xkcd
    goodness, click on the link in the figure caption and hover your
    mouse over the cartoon.

Any errors in this tutorial are my own.[^unless]

[^unless]: Unless someone else wants to take responsiblity for a given blunder on my part, in
which case I'll gladly cede the privilege. 

**Which**

At the end of the summer, let me know which parts you found useful or useless
to you. I'll consider your suggestions for next year's workshop.

Have fun!

*-- [Bill Seligman](http://www.nevis.columbia.edu/cgi-bin/ewarn.pl?seligman&nevis.columbia.edu)*