A small Internet phenomenon on Futaba Channel, the OS-tan (OS for Operating System, and the Japanese "-tan" (??) which is an overly cute mispronounciation of, specifically a child's slurring of "-chan" (???), a diminutive honorific for a person) or simply OS Girls are the personification of several OSes, most famously Windows, by various amateur Japanese artists. A pure fan creation, the appearance of each character is generally consistent across artists. OSes are almost always portrayed as women, the Windows girls usually as sisters, despite sometimes seeming the same age.
Longhorn
This character doesn't have many pictures and not much is known about her as she is based on Microsoft Operating System Windows Longhorn, which is still in development. One picture shows her as a girl with dark blue hair and two horns extending from the back of her head to the front; her clothing is all white except across the shoulders where it's black and there are the letters L and H on her chest. A design becoming more common is a young girl with long brown hair in pigtails wearing one or two clips featuring an orange and black logo resembling a stylized bull's head.
WindowsXP
XP is a sexy, dark-haired girl wearing the XP logo as a hair ribbon. As XP is sometimes criticized for bloating a system and being very pretty without being equally as useful, XP-tan wears very little and has large breasts. Also, as XP uses up large amount of memory, XP-tan eats a lot, usually holding a large empty bowl with the word "memory" on it, but still requests more. A rare variant that represents XP Home features a more reserved look, akin to 2K Pro-tan. She has XP shaped hairclips instead of a ribbon, and tends to wear her hair up in a short ponytail. An even rarer variant, for XP Media Center Edition, has short hair and small earrings in the style of XP Professional's hairclip.
Max OS X
The Mac OS X girl is often portrayed as cat-eared, following with the Apple "wild cat" naming tradition. (Every Mac OS X release has a codename like "Jaguar", "Panther" and so on.) Otherwise, she is shown as an older variation of the Mac OS 9 girl, wearing a platinum white coat and a wireless AirPort device fashioned as a hat. She is occasionally shown holding a publication of some sort, as Macs are often used for desktop publishing.
Linux
A girl with a penguin-like helmet and flippers, a reference to Linux's penguin mascot Tux. Her helmet usually has horns on it, likely a reference to the GNU project which is often associated with Linux. The "gear-teeth" on the helmet is a reference to KDE, a common desktop environment used with Linux. She is often seen with a spear that has flags attached representing the GRUB, LILO and tools for Linux.
read more: http://en.wikipedia.org/wiki/OS-tan