In recent years a diverse array of e-book formats have risen. The major e-book formats as of today include PDF, EPUB, MOBI, KF8, iBook, and others. Though some of these formats are tied into specific devices, they can be easily converted into one another using software programs like Calibre. For example, any of the above formats can be converted into a format compatible with the iPad with conversion software. Most Android tablets have the capability to read formats used by Kindle, Nook, and Google Play Books. What’s more, these formats can also be read on computers running on conventional Windows or Mac operating systems. For instance, Adobe Digital Editions, which is free to download, allows PCs to read EPUB format. Apple’s own e-book reader iBooks “can display movies, interactive widgets, and movable 3-D objects. When the reading device is held vertically, iBooks has a traditional book appearance. Multimedia extras appear in the horizontal orientation.” The two main advantages of e-books cited by library patrons were “searchability and around-the-clock availability. The most frequently cited disadvantages were the difficulty of navigation and loss of ability to perform customary research practices such as perusing and shelf-browsing because of e-books’ lack of physicality.