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When your Raspberry Pi arrives, you’ll see that it’s a circuit board, with components and sockets stuck on it, as shown in Figure 1-2. In an age when most computing devices are sleek and shiny boxes, the spiky Pi, with tiny codes printed in white all over it, seems alien. That’s a big part of its appeal, though: Many of the cases you can buy for the Raspberry Pi are transparent because people love the look of it.

FIGURE 1-2: The Raspberry Pi 3 Model B (top left), Model A+ (top right), and Pi Zero W (bottom).

Over the years, the Raspberry Pi has evolved, increasing its memory, improving its performance, and adding features. So which one should you get? Here’s an overview designed to help you decide:

❯❯ Raspberry Pi 3 Model B: The third generation of the Raspberry Pi, it represents the best all-round Raspberry Pi at the time of writing. According to the Raspberry Pi Foundation, it is 50 to 60 percent faster than the previous model, and ten times faster than the original Raspberry Pi. It includes 1GB of memory, four USB ports, built-in Wi-Fi and Bluetooth, and an Ethernet port for a wired Internet connection. It has 40 General Purpose Input/Output (GPIO) pins, which you can use to connect to your own electronics projects. Like previous Pi models, it's about the size of a credit card. As with any current Raspberry Pi, it uses a MicroSD card for storage. If you're not sure which model to get and your budget allows, get this one. It represents the fastest performance, and offers the best experience on the desktop. Its price is around $35 (about £30).

It’s called the Model B, incidentally, as a tribute to the BBC Microcomputer that was popular in the U.K. in the 1980s. It’s sobering to think that the BBC Micro cost about ten times the price of a Raspberry Pi, which, thanks to 35 years of progress in computer science, has more than 7,800 times more memory.

❯❯ Raspberry Pi 1 Model A+: A cut-down model, it is ideal for projects that need lower power consumption – typically battery-based projects. It is suitable for robots and projects in remote locations, where a wired electricity supply isn’t viable and batteries must be used instead. It does not have an Ethernet socket, and only has one USB port, although you can connect it to a USB hub to use more devices simultaneously. It does have the full complement of 40 GPIO pins, though, so you should find that your projects and add-ons work with it. Like the Model B, it includes an audio output (headphones-style) socket. This model has 512MB of memory and a price of $20 (or £20). The Model A+ is slightly shorter on the long side than the Raspberry Pi 3, measuring 6.5 centimeters by 5.5 centimeters.

❯❯ Raspberry Pi Zero: The Raspberry Pi Foundation astounded everyone when it gave this computer away with the print edition of its magazine The MagPi. The Raspberry Pi Zero measures 6.5 centimeters by 3 centimeters, is extremely lightweight, and has 512MB of memory and one Micro USB port. If you want to use the GPIO, you'll need to solder or affix your own pins, available separately. (You can read about adding GPIO pins to the Pi Zero in Chapter 16.) You'll also need a converter for the Mini HDMI socket, and for the Micro USB socket, so you should expect to spend a bit more than the price of the Pi (and have a bit more complexity in your setup). Billed as the $5 computer, the Raspberry Pi Zero has at times been difficult to get hold of, which is perhaps not surprising given the phenomenal demand for it.

❯❯ Raspberry Pi Zero W: Released in February 2017, the Raspberry Pi Zero W added Wi-Fi and Bluetooth, and compatibility with the Raspberry Pi Camera Module. The Pi Zero W costs around $10 (or about £10). If you're happy to solder your own GPIO pins, or you don't need them, the Raspberry Pi Zero or Zero W represents a great entry point to the Raspberry Pi family. After the Raspberry Pi Model 3, the Pi Zero W is our recommended best buy.

Of course, the older Raspberry Pis are still out there. Recent models usually remain in production while there is demand, and you can buy secondhand versions online from websites such as eBay. Generally speaking, the newer the model, the faster its performance. Memory upgrades have made a difference, as well as the use of more powerful processors, as the Pi has evolved. There are plenty of uses for the Pi that don't need especially fast performance, though, so you might find that an older Pi is perfect for your project. The older models are described in this list:

❯❯ Raspberry Pi 1 Model B with 256MB memory: Although it’s called Model B, this was the first Raspberry Pi to be released, in February 2012. The Raspberry Pi Model B features an Ethernet connection for the Internet and two USB ports. It uses an SD card for storage.

❯❯ Raspberry Pi 1 Model B with 512MB memory: Released in October 2012, the Raspberry Pi Model B had twice the memory capacity. This improved the speed of some software, especially applications that used images heavily.

❯❯ Raspberry Pi 1 Model A: The Model A, released in February 2013, is a stripped-down version of the Model B. It has just one USB port and doesn’t have an Ethernet port for connecting to the Internet. It has 256MB of memory.

❯❯ Raspberry Pi 1 Model B+: The Model B+, released in July 2014, has been described by the Raspberry Pi Foundation as “the final evolution of the original Raspberry Pi.” It runs all the same software as the previous versions of the Raspberry Pi, but it has four USB ports, more GPIO pins for connecting electronics projects to the Pi, and lower power consumption and better audio than the Model B. In common with the Model B, it has 512MB of memory. Although all previous versions use SD cards for data storage, the Model B+ introduced the smaller MicroSD cards, which are now standard on the Raspberry Pi.

❯❯ Raspberry Pi 2 Model B: Launched in February 2015, this model doubled the memory on the Model B+ to 1GB. It increased performance, compared to the Model B+, while retaining its physical features. Over the years the Pi's performance has been improved through new software releases as well as updates to the hardware. The Pi 2 represents an immediately noticeable speed-up, compared to the Model B+.

If you're using anything earlier than the Model B+, you'll need full-size SD cards (not MicroSD) for storage, and you'll only have 26 GPIO pins to play with. Current add-ons are unlikely to be compatible with the early boards, so check their requirements before you buy.

In this book, we offer guidance on older models where possible but will assume you're using at least a Model B+ for the projects. For best performance, we recommend using a current model, if possible.

You’ll also see the Raspberry Pi Compute Module in the online stores alongside the Raspberry Pi, but this is something quite different. It’s aimed at engineers creating industrial applications (known as embedded systems) or products based on Raspberry Pi technology. We only mention it here in case you wonder what it is: It’s not covered further in this book, and it’s almost certainly not what you want to buy for your first Raspberry Pi.

The Raspberry Pi was made possible in part by the advances in mobile computer chips that have happened in recent years. At its heart is a Broadcom chip (BCM2835, BCM2836, or BCM2837) that contains an ARM central processing unit (CPU) and a Videocore IV graphics processing unit (GPU). The CPU and GPU share the memory between them. The GPU is powerful enough to be able to handle Blu-ray quality video playback.

Instead of running Windows or Mac OS, the Raspberry Pi uses an operating system called Linux. It’s a leading example of open source, a completely different philosophy to the commercial software industry. Rather than being created within the heavily guarded walls of a company, with its design treated as a trade secret, Linux is built by companies and expert volunteers working together. Anyone is free to inspect and modify the source code (a bit like the recipe) that makes it work. You don’t have to pay to use Linux, and you’re allowed to share it with other people, too.

You probably won’t be able to run the software you have on your other computers on your Raspberry Pi. It won’t run Windows or Mac software, and not all Linux software works on the Raspberry Pi. But a lot of Linux software that is compatible with the Raspberry Pi is available and is free of charge.