Developer Bohemia Interactive warns that this alpha version of the game, which runs on Windows only, is very much a "work in progress" and does not advise people purchase the game in this state unless they are interested in watching the game's development.
“DayZ Early Access is your chance to experience DayZ as it evolves throughout its development process," reads the game's description. "Be aware that our Early Access offer is a representation of our core pillars, and the framework we have created around them. It is a work in progress and therefore contains a variety of bugs. We strongly advise you not to buy and play the game at this stage unless you clearly understand what Early Access means and are interested in participating in the ongoing development cycle.”
The standalone version of DayZ was originally announced in 2012, and was intended to be released in alpha form before the end of last year. Compared to its original release as a mod for ArmA II, the long-delayed DayZ standalone will feature a new client/server architecture, gear deterioration, locational damage, and a new inventory system.