Raspberry Pi may sound like the name of a math-based dessert. But it is actually one of the hottest and cheapest little computers in the world right now. Almost one million of these $35 machines have shipped since last February, capturing the imaginations of educators, hobbyists and tinkerers around the world.
The story of the Raspberry Pi begins in 2006 when Eben Upton and other faculty members at the University of Cambridge in Britain found that their incoming computer science students were ill prepared for a high-tech education. While many students in the previous decade were experienced electronics hobbyists by the time they got to college, these freshmen were little more than skilled Web designers.
Easy-to-use, modern PCs hide most of the nuts and bolts behind a pleasing interface. Mr. Upton posited that parents did not want their children to destroy their expensive computers by experimenting with their insides. But a cheaper machine would be fair game for messing around.
The Raspberry Pi -- about 3 inches by 2 inches and less than an inch high -- was intended to replace the expensive computers in school science labs. For less than the price of a new keyboard, a teacher could plug in the Pi and connect it to older peripherals that might be lying around. But because Pi initially ran only Linux, a free operating system popular with programmers and hobbyists, students would have a learning curve.
The Raspberry Pi Foundation began selling the computers in February of last year. They soon could not keep them in stock.
"We honestly were thinking of this as a 1,000- to 5,000-unit opportunity," Mr. Upton said. "The thing we didn't anticipate was this whole other market of technically competent adults who wanted to use it. We're selling to hobbyists."
One Pi owner, Dave Akerman, of Brightwalton, England, even sent a Raspberry Pi to the upper atmosphere, floating it 40,000 meters up using a weather balloon. There he was able to take live video, photos and measurements.
"Now every primary school in the world can take pictures from near space," Mr. Upton said. "You give people access to this tool and they do great things."
Picking up a Raspberry Pi is not as easy as popping into a store. The Pi is so popular that many distributors are constantly out of stock. It is also difficult to find them online.
"The old phrase 'selling like hot cakes' needs to be updated to 'selling like Raspberry Pi's,' " said Limor Fried, founder and engineer at Adafruit Industries, a distributor of the Pi. "We've sold tens of thousands in weeks." Ms. Fried is actually using a few Raspberry Pis and custom software to streamline her receiving and shipping system.
The Pi costs $35, or $25 for an older model, and comes as a bare circuit board. Leaving the defenseless little thing unclothed is tantamount to Pi abuse, so you should also pick up a plastic enclosure. Adafruit sells clear plastic enclosures for $15, and Polycase.com sells a solid, opaque plastic case for $17.
The Raspberry Pi works best with an HDMI-compatible monitor and USB keyboard and mouse. It is powered via a standard USB cable -- just like the one that charges your phone -- and it includes an audio-out port for connecting a set of speakers, plus an RCA jack if you don't have a digital TV or monitor available.
There is no on-off switch. To turn it off, you simply pull out the power cable.
The Raspberry Pi will not do much out of the box. Because it has no onboard storage or operating system, you will need to copy the necessary software to a high-capacity SD memory card. A four-gigabyte card usually works well, but you may want more if you plan on loading applications or games.
There are a number of available operating systems for the Raspberry Pi. On the official Web site, raspberrypi.org, you'll find something under downloads called Raspbian, a Raspberry-flavored version of the Debian operating system that includes tools for beginners. Raspbian uses an interface that will be familiar to users of Windows or Linux.
Adafruit has its own version of the Pi operating system called the Raspberry Pi Education Linux Distro at learn.adafruit.com. It comes with a child-friendly browser.
Also available are programs that you can use to add additional features to the Raspberry Pi, including Wi-Fi support (an add-on peripheral is required) and hardware controllers for connecting your Pi to sensors, motors and more.
Truly adventurous Raspberry Pi fans can even turn the product into a small home media center. Because the Pi has a powerful graphics chip on board, users have been able to stream video and photos to their big-screen TVs using little more than a Pi and a Linux program like RaspbMC at www.raspbmc.com. This fully-featured media center lets you stream video from a hard drive on the network and supports AirPlay, Apple's proprietary video and audio streaming system.
Mr. Upton said the plan was to develop the Pi's software rather than the hardware. "If you improve the software, everyone can use it," he said. "If you change the hardware, you leave a million buyers behind."
Mr. Upton said he was "blown away" by the reception the Pi had gotten online.
"I'm not aware of a company that has gone from a standing start to a million in a year," he said. "It's quite a wild ride. I don't get a lot of sleep at the moment."
When asked if he planned to give a Pi to his children, Mr. Upton said he and his wife, Liz, who works with him on the project, had not had time to start a family.
"We're busy, so we're glad we haven't had kids yet," he said. "It's Pi and then kids, not kids and then Pi."
This article originally appeared in The New York Times.