players, software that is capable of seamlessly transferring files between the player and the computer). For later players, however, these are usually available online via the manufacturers' websites, or increasingly natively recognised by the operating system through Universal Mass Storage (UMS) or Media Transfer Protocol (MTP). Hardware Storage As with DAPs, PMPs come in either flash or hard disk storage. Storage capacities have reached up to 64 GB for flash memory based PMPs, first reached by the 3rd Generation iPod Touch, and up to 1 TB for hard disk drive PMPs, first achieved by the Archos 5 Internet Tablet. A number of players support memory card slots, including CompactFlash (CF), Secure Digital (SD), and Memory Sticks. They are used to directly transfer content from external devices, and expand the storage capacity of PMPs. Interface A standard PMP uses a 5-way D-pad to navigate. Many alternatives have been used, most notably the wheel and touch mechanisms seen on players from the iPod and Sansa series. Another popular mechanism is the swipe-pad, or 'squircle', first seen on the Zune. Additional buttons are commonly seen for features such as volume control. Screen Sizes range all the way up to 7 inches (18 cm). Resolutions also vary, going up to WVGA. Most screens come with a colour depth of 16-bit, but higher quality video-oriented devices may range all the way to 24-bit, otherwise known as true colour, with the ability to display 16.7 million distinct colours. Screens commonly have a matte finish but may also come in glossy to increase colour intensity and contrast. More and more devices are now also coming with touch screen as a form of primary or alternate input. This can be for convenience and/or aesthetic purposes. Certain devices, on the other hand, have no screen whatsoever, reducing costs at the expense of ease of browsing through the media library. Radio Some portable media players include a radio receiver, most frequently receiving FM. Features for receiving signals from FM stations on MP3 players are common on more premium models. Other features Some portable media players have recently added features such as simple camera, built-in game emulation (playing Nintendo Entertainment System or other game formats from ROM images) and simple text readers and editors. Newer PMPs have been able to tell time, and even automatically adjust time according to radio reception, and some devices like the 6th-gen iPod Nano even have