The Raspberry Pi is a small cheap single-board computer. It offers a graphical user interface very similar to Microsoft Windows. It's also possible to run it "headless" - without a keyboard, mouse and monitor. In that mode you control it using over a network connection a powerful command line interface that mimics the one provided by the UNIX operating system. That was designed about fifty years ago and has remained very stable since.
There are all sorts of versions of the Raspberry Pi, aimed at different applications. The Raspberry Pi 4 model B and the Raspberry Pi 5 can be used as desktop computers. The cost for a complete system is around £100.
Many companies supply Raspberry Pis. I'm based in the UK and I bought one from here.
Raspberry Pis are usually sold as kits, which puts off some potential buyers. However, the assembly process is simple and quick. You can get a Pi up and running within about half an hour and it requires very few IT skills.
The safest assumption for me is that you have never done anything like this before, so I give the instructions in stages, explaining stuff that you may not already understand. That can get a little long-winded. Don't be daunted, just go through the pages step by step. If you already know the stuff, just skip over it.
If you're going to run your Pi headless then you need to be able to connect to it over the network and control it from another computer. To allow that you need to create a couple of files on that other computer. As we'll see, you need to do that first. I explain what to do here.
The Pi uses a micro-SD card for its permanent storage. These are often used in digital cameras to store pictures. If you've used a digital camera you probably know all about them. If you've only used the camera in your phone, maybe not. I give bit more detail about that later.
There are lots of videos on YouTube explaining how to assemble a Raspberry Pi and install Linux on it. This one is quite good, except that it assumes that you know all about using an SD card.
Discussions about the Pi often suffer from another assumption, which is that you already understand how to use one, in particular, how to use the command line interface and the commands that it runs. Most people don't, of course.
This problem was recognised when the UNIX system was developed in the 1970s. They produced a piece of software called learn which provides basic training on the commands and how to run them. Fifty years on the learn software looks a bit antiquated but it still works well because it gets the user to run commands and experiment on a real UNIX system.
The learn system fell out of use but a few years ago I got it working under Docker. Docker provides a UNIX system running within another system such as Microsoft Windows, so now you can run learn on your Windows computer before you even buy your Raspberry Pi. Find out all about the learn software here.
Once you get your Raspberry Pi kit, the first step is to "burn" (write) the operating system onto the micro-SD card. You can do that on a Windows computer too.
The micro-SD card
Burning the operating system image
Assembling the kit
Setting IP Addresses