# Walkthrough: The ROOT browser 
**(5 minutes)**

:::{note}
The ROOT browser is a useful tool, though it can be a 
bit clumsy at times. Let's give it a try. 
:::

One way to retrieve the contents of file "c1.root" is to use the ROOT
browser. Start up ROOT and create a browser with the command:[^rbrowser]$^,$[^f29]

    [] TBrowser tb

:::{figure-md} tbrowser-fit
:align: center

<img src="ExampleBrowser.png" alt="Example TBrowser image" width="75%">

When I start the `TBrowser`, this is what I see. Your window won't be quite the same, if for no other reason that my home directory has more files and sub-directories than yours does... at least for now!
:::


In the left-hand pane, scroll to the folder with the same name as your
home directory.[^f30] Scroll through the list of files. You'll notice
special icons for any files that end in ".C" or ".root". If you
double-click on a file that ends in ".C": 

   - if the **Editor** tab is in
     front ROOT will display its contents in the editor window; 

   - if the **Canvas** tab is in front, ROOT will execute its
     contents. 

Click on the **Canvas** tab, then double-click on **c1.C** to see what
happens.

Now double-click on **c1.root**, then double-click on `c1;1`.

:::{note}
Don't see anything? Click on the **Canvas 1** tab in the browser window.

What does "c1;1" mean? You're allowed to write more than one object
with the same name to a ROOT file (this topic is part of a lesson later
in this tutorial). The first object has ";1" put after its name, the
second ";2", and so on. You can use this facility to keep many
versions of a histogram in a file, and be able to refer back to any
previous version.

At this point, saving a canvas as a ".C" file or as a ".root" file
may look the same to you. But these files can do more than save and
re-create canvases. In general, a ".C" file will contain ROOT commands
and functions that you'll write yourself; ".root" files will contain
structured objects such as n-tuples.

As nifty as the ROOT browser is, for the work that you'll do this summer
you'll probably reach the limits of what it can do for you, especially
if you have to work with large numbers of files, histograms, n-tuples, or
plots.

Still, it's nice to know that it's there, in case (as the name suggests)
you want to browse quickly through a couple of ROOT files.
:::

[^rbrowser]: If you're not at Nevis, depending on the details of your ROOT set-up, you
    may see something similar with a title that reads `RBrowser`. This is the next-generation
    ROOT Browser. It doesn't have all the bells-and-whistles of the original `TBrowser`
    yet; for example, you can't right-click on the name of an n-tuple to start the
    {ref}`TreeViewer <treeviewer>`. 

    It won't be hard to figure out how to use the `RBrowser` on your own. If you really
    want to see the `TBrowser` as used in this tutorial, quit ROOT, edit the file
    `~/.rootrc`, and add the line:

        Browser.Name: TRootBrowser

    Save the file and start up ROOT again. You should see the `TBrowser` from now on. 

[^f29]: You may see someone using this command instead:

        [] new TBrowser
    
    The difference is slight, and only matters if you're experienced
    with C++. (If you are experienced with C++: what is that difference?
    {ref}`Here's a hint <pointers>`.)

[^f30]: If you have a Nevis temporary account, the folder hierarchy
    may be puzzling to you; your home directory will be in
    `/nevis/milne/files/<account>`. For now, don't worry about
    this. If you'd like to know more, there's [the Nevis wiki
    automount
    page](https://twiki.nevis.columbia.edu/twiki/bin/view/Main/Automount).