Arena is a freeware

Freeware

Freeware is computer software that is available for use at no cost or for an optional fee, but usually with one or more restricted usage rights. Freeware is in contrast to commercial software, which is typically sold for profit, but might be distributed for a business or commercial purpose in the...

 GUI for chess engines by Martin Blume and runs on Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

.

It supports the protocols UCI

Universal Chess Interface

The Universal Chess Interface is an open communication protocol that enables a chess program's engine to communicate with its user interface....

 and Chess Engine Communication Protocol

Chess Engine Communication Protocol

The Chess Engine Communication Protocol is an open communication protocol that enables a chess engine to communicate with its user interface....

 to communicate with the chess engines that provide the computer enemies. Arena therefore supports a vast amount of chess engines, e.g. top-rated Rybka

Rybka

Rybka is a computer chess engine designed by International Master Vasik Rajlich. , Rybka is one of the top-rated engines on chess engine rating lists and has won many computer chess tournaments...

.

The standard package ships with the engine SOS 5.1 which got rank 2 in the Computerschachmeisterschaft 2003 and it has an Elo

Elo rating system

The Elo rating system is a method for calculating the relative skill levels of players in two-player games such as chess. It is named after its creator Arpad Elo, a Hungarian-born American physics professor....

 ranking of more than 2500 points.

The following file formats are supported: EPD, PGN

Portable Game Notation

Portable Game Notation is a computer-processible format for recording chess games ; many chess programs recognize this extremely popular format due to its being stored in plain text.-History:...

 and FEN

Forsyth-Edwards Notation

Forsyth–Edwards Notation is a standard notation for describing a particular board position of a chess game. The purpose of FEN is to provide all the necessary information to restart a game from a particular position....

.