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Small, affordable single-board computer for hobbyists and students
Plenty of I/O ports
Wide choice of operating systems
Needs fan and case
No built-in storage
Alternate operating systems need higher-spec, more expensive versions
The Raspberry Pi Foundation aims to put computing tools in the hands of people all over the world, using low-cost single-board computers to make hardware and software accessible to as many as possible. It's a model reminiscent of the early days of the home computer, with cheap, easy-to-program and affordable hardware. Those computers inspired a generation, and Raspberry Pi wants to do the same today.
Setup & configuration
Getting started with a Raspberry Pi is easy enough. You can buy a Pi 4 from many different vendors, from £33.90 for a 2GB device ($35 in the US) to £73.50 for the 8GB option ($75 in the US). If you just buy a bare board, you'll need to provide a power supply and a MicroSD card to get started. Setup also requires a micro-HDMI cable, a keyboard, and a mouse (unless you intend to remote-control your Pi from a PC). Alternatively, you can buy a kit that includes much of what you need to get started, with a basic starter kit coming in at £58 ($68.20 in the US) and a more featured desktop kit with keyboard, mouse, and case for £116 ($120 in the US).
I've been using a Logitech wireless USB media keyboard with my devices, as it has a built-in trackpad so I don't need to worry about cables. The Pi 4 will also work with Bluetooth devices (there's support for Bluetooth 5.0 and BLE), giving you plenty of options for keyboards and mice. Other connections include a camera port and a display connector for integrated displays, both intended for DIY IoT projects.
Working with a MicroSD card can be a limitation, although they do make it easy for schools and code clubs to have a low-cost set of images that can be given to each student and replaced whenever they fail or are lost. You can start with as little as 8GB of storage, but 16GB or 32GB is a better option in practice, with Raspberry Pi OS automatically resizing its partitions to fit all sizes of storage.
Initial firmware builds on the Pi 4 didn't support working with USB SSD drives, relying on MicroSD cards. While they're a cheap solution, they are unreliable, and if you don't back up your system regularly, you're at risk of data loss when (not if!) the device fails. MicroSD cards aren't designed for PC workloads, and it's easy to exceed their write cycles.
The introduction of USB boot support changed things dramatically, and you can now write boot images to SSD drives using the PC-based Raspberry Pi Imager, ready for use. If you have an older Raspberry Pi 4 you may need to use the console-based configuration tool to turn on USB-boot support, but it should be on by default on newer hardware.
Performance: choosing the right Pi for the job
Performance is good enough for most purposes, and while you can happily run most software you shouldn't expert performance. The quad-core ARM Cortex A72 SoC is clocked at 1.5GHz, and in our tests an 8GB Pi 4 achieved a single core score of 183 and a multi core score of 576 with the beta ARMv7 builds of Geekbench 5. In comparison, a low-end Surface Go scored 357 and 906 respectively.
I've been using two different Pi 4s for different purposes. An 8GB system has been used as a low-cost Linux desktop, using the built-in HDMI to drive a monitor, with a wireless mouse and keyboard. The other is a headless 2GB system that runs an ADS-B receiver using a custom Linux, used to develop and manage an open-source project I maintain. That's perhaps the key value of Raspberry Pi -- its flexibility.
It's a powerful platform for building your own hardware and software. The GPIO ports allow you to extend the device with your own and third-party hardware, usually referred to as HATs (Hardware Attached on Top). You can start with Raspberry Pi's own Raspberry Pi OS, a custom version of Debian, that comes preconfigured with basic programming tools and a list of recommended educational and programming tools. There's enough here to get started, but as Raspberry Pi OS is an ARM Linux you can install any ARMv7 binaries you want. The Pi's desktop environment includes a software installer, or you can add new repositories and install software from the command line.
One important issue, especially if you're planning on running a Linux desktop, is heat. The Pi 4's processor can run hot under load, so I'd recommend using a fan or a heatsink case to keep it cool. I've ended up putting all my devices in Argon40's ArgonOne cases. These provide a software-controlled fan and a user-configurable power button, as well as using an extender to move the HDMI ports so that all the Pi's ports are at the rear of the case. That makes it a lot easier to manage cables, especially if you're using both HDMI ports to drive two monitors.
Raspberry Pi's 4 is going to be the Foundation's flagship single board computer for at least another year, as it has indicated it will be concentrating on software for the rest of 2021. That should allow Raspberry Pi OS to continue to mature, with regular updates to both the device firmware and the Linux OS. While the OS remains 32-bit, you can install alternatives like Ubuntu, which come with full 64-bit support, although here you will probably want to use an 8GB Pi.
As an educational and introductory computer, it's hard to beat the Raspberry Pi. Each new release has managed to do more without fundamentally changing the size of the board, adding more and more features while still supporting the same interface for third-party hardware. As someone who grew up with 1980s 8- and 16-bit computers, there's a certain nostalgia in a device like this, but it's also hardware that clearly looks forward, building on its heritage and aiming to encourage more developer and engineers.
If the Sinclair Spectrum and the Acorn BBC B are the machines that educated a generation, the Raspberry Pi 4 is clearly hardware that aims to do the same for the next. If the Raspberry Pi 4 is anything to go by, there's a good chance that it will succeed. It's the board to buy if you want a low-cost PC for programming and IoT projects, or to get children learning the basics of computing -- from Minecraft to Python and beyond.