An ebook, or e-book, is an electronic book, which may be a digital version of a printed book or a publication that only has a digital existence. An ebook is made to be read on a computer or a more portable device. A number of ebooks can be read on any PDA. However, an ebook reader is a dedicated device for reading ebooks. One type of ebook reader is the pocket ebook reader.
Since ebook readers with “pocket” in their name have a maximum diagonal screen size of 6-in (15.24 cm) — and a number have a 5-in (12.7 cm) diagonal screen size — it can be assumed that any other ebook reader of this size can be considered a pocket ebook reader. This contrasts with the 9.7 in (24.64 cm) screen of the Apple® iPad® and Amazon® Kindle® DX and the 10.2 in (25.91 cm)screen of the iRex® Digital Reader 1000®, the largest of the ebook readers. Pocket ebook readers have various operating systems, including Android®, versions of Linux® including MontaVista® Linux®, and Windows® CE.
Some types of pocket ebook reader focus entirely on ebook reading, while others have additional features. Ebook-oriented features available on various brands of pocket ebook reader include a touchscreen, a dictionary, a card reader, and text-to-speech capability. Other extended features include a web browser, WiFi, 3G, and Bluetooth®. Some play MP3s and display images.
There are a wide variety of document formats for the pocket ebook reader, and readers differ in which ones they work with. Some of the formats that are often found include PDF (Portable Document Format), TXT (text files extension, HTML (HyperText Markup Language), Mobipocket®, RTF (Rich Text Format), and ePub (electronic publication).Other differences include the amount of internal memory, which can be as little as 256 MB (Megabytes) and as much as 2 GB.
The screen resolution on pocket ebook readers is 600 x 800 pixels, but they may have different ppi values (pixels per inch). The number of grayscale levels is between 4 and 16. Battery life is measured in page turns and is given as an “up to” amount, the best of which is “up to 8000.” Recharge time varies between 3.5 hours and 4 hours, more or less. The lightest way about 6.14 oz (174 g) with heavier ones weighing 12.1 oz (343 g). Some are quite thin, with a thickness of only .4 in (1.02 cm).