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ROOT Logo.png
Atlas ROOT plot.png
The ATLAS experiments presented on July 4th 2012 the status of the Standard Model Higgs search. All the plots presented that day were done using ROOT.
Developer(s) CERN
Stable release 5.34/21 & 6.02/00 / October 5, 2014; 5 months ago (2014-10-05)
Written in C++
Operating system Windows, OS X, RHEL, Solaris, IBM AIX
Platform IA-32, x86-64
Size 42–144 MB
Type Data analysis
License LGPL/GPL

ROOT is an object-oriented program and library developed by CERN. It was originally designed for particle physics data analysis and contains several features specific to this field, but it is also used in other applications such as astronomy and data mining.


CERN maintained a program library written in FORTRAN for many years; development and maintenance were discontinued in 2003 in favour of ROOT, written in C++. ROOT development was initiated by René Brun and Fons Rademakers in 1994. Some parts are published under the LGPL, and others are based on GPL software and thus are also published under the terms of the GPL. It provides platform independent access to a computer's graphics subsystem and operating system using abstract layers. Parts of the abstract platform are: a graphical user interface and a GUI builder, container classes, reflection, a C++ script and command line interpreter (CINT), object serialization and persistence.

The packages provided by ROOT include those for

The CMS experiments presented on July 4th 2012 the status of the Standard Model Higgs search. All the plots presented that day were done using ROOT.

A key feature of ROOT is a data container called tree, with its substructures branches and leaves. A tree can be seen as a sliding window to the raw data, as stored in a file. Data from the next entry in the file can be retrieved by advancing the index in the tree. This avoids memory allocation problems associated with object creation, and allows the tree to act as a lightweight container while handling buffering invisibly.

ROOT is designed for high computing efficiency, as it is required to process data from the Large Hadron Collider's experiments estimated at several petabytes per year. As of 2009 ROOT is mainly used in data analysis and data acquisition in high energy physics experiments, and most current experimental plots and results in those subfields are obtained using ROOT.

The inclusion of a C++ interpreter (CINT until version 5.34, cling from version 6.00) makes this package very versatile as it can be used in interactive, scripted and compiled modes in a manner similar to commercial products like MATLAB.


Criticisms of ROOT include its difficulty for beginners, as well as various aspects of its design and implementation. Frequent causes of frustration include extreme code bloat, heavy use of global variables,[1] and a perverse class hierarchy.[2] From time to time these issues are discussed on the ROOT users mailing list.[3][4] While scientists dissatisfied with ROOT have in the past managed to work around its flaws,[5] some of the shortcomings are slowly being addressed by the ROOT team. The CINT interpreter, for example, has been replaced by the cling interpreter,[6] and numerous bugs are fixed with every release.

Applications of ROOT[edit]

Several particle physics experiments have written software based on ROOT, often in favor of using more generic solutions (e.g. using ROOT containers instead of STL).

See also[edit]

External links[edit]