Build a Computer

• TASK: Build a computer in order to understand how a computer works and to be able to diagnose and repair one when it breaks.
• CONDITIONS: Given a Raspberry Pi, a USB keyboard, a USB mouse, a USB power cable, an HDMI monitor, an 8GB microSD card, and a working computer that can read and write the microSD card.
• STANDARD: You must be able to assemble the parts and install the operating system so that you can use the computer.

Computer technology continues to blaze forward at an amazing rate. So much so, that by the time you’re reading this, there is a good chance that it’s become outdated. With that in mind, I’m going to try to focus not so much on technical detail as much as general concepts as those stay relatively constant. By following this set of instructions, you will be able to turn a pile of parts into a working computer, but more importantly, you’ll be able to understand how it all works.

Common Computer Parts
A computer is a compilation of various parts. Some computers have more or different parts than other computers depending on their purpose, but there are some parts that every computer has to have.

Motherboard
The motherboard is the large circuit board into which all of the other parts connect. In this instruction, the Raspberry Pi is the motherboard. Motherboards have a multitude of connectors and adaptors each with its own purpose. The Raspberry Pi board is powered by a MicroUSB port similarly to many smartphones. Plugging the power cord in will turn the computer on and unplugging it will turn it off.

Central Processing Unit (CPU)
The CPU is the brain of the computer. CPU speed is typically measured in gigahertz (GHz) and in the number of cores. In the case of the Raspberry Pi, the CPU is already built in to the board so you don’t have to worry about buying a separate one.

Random Access Memory (RAM)
RAM is the short-term memory of the computer.  The computer uses RAM for quickly storing and retrieving data. As long as the computer is turned on, RAM stores data, but when the computer is turned off, any data  stored in RAM is lost. Saving a file will transfer it from RAM onto a hard disk which we’ll talk about later. RAM is typically measured in gigabytes (GB) and can come in a number of different form factors. As with the CPU, the Raspberry Pi comes with RAM already built in to the board so you don’t have to worry about it.

Hard Drive (HD)
Hard drives are the long-term memory of the computer. Data that is saved on the hard drive will exist through reboots and until it is deleted. Hard drive size is typically measured in gigabytes or terabytes (TB). The Raspberry Pi’s hard drive is the microSD card. The hard drive is where the computer’s operating system, user files, and applications software are stored.

Common Accessories
There are a few accessories that need to be connected to allow the human to interact with the computer. It’s easy to think of these accessories as being the computer since they are the way that we interact with it, but these parts actually have very little to do with the computer and can be easily replaced.

For this activity, you’ll need a USB keyboard and mouse and an HDMI monitor. These three accessories will provide a basic interface between you, the human, and the computer. If any one of these accessories is broken, the computer will continue to work, you just won’t be able to interact with it.

Install The Operating System (OS)
A computer’s operating system is a basic set of software to make the computer work. Some of the more well-known OSs are the Mac and Windows families. Less well-known, but equally capable, are the Linux families of OSs. This activity will use Raspbian, a Linux-based OS as there are much fewer legal and price restrictions associated with it.

In order to install Raspbian on the microSD card, you’ll need to have access to a working computer and the internet. Similarly to computer hardware, operating system technology advances at a blistering rate and there is the possibility that these instructions will be outdated by the time you read them. You can find the most current techniques by searching for “install raspbian”.

At the time of this writing, a project exists called PiBakery that is designed to simplify the process of installing Raspbian to a microSD card. To use PiBakery, go to http://www.pibakery.org/, click on the download page, and download the version for the computer that you’re using. The PiBakery website should have the most current set of instructions for using their software on their site.

Assemble The Computer
With the OS installed to the microSD card and all the parts and accessories ready, all that’s left is to simply put it all together. The ports on the RaspberryPi, as with most computers, are designed so that you can’t plug something into the wrong port. There is a saying with cats that if “I fits, I sits”. This holds true with computers as well. If the part or cable fits the adaptor or port, then it’s in the right place.

Plug in the microSD card, the keyboard and mouse, the monitor, and finally, the power cord. You should see the monitor light up and be able to watch the computer boot up.

Extra Credit
If you want to get your computer on the internet, you can use a Category 5 (CAT5 or RJ45) ethernet cable and plug it into your home router or, if your model of RaspberryPi has at least three USB ports, you can buy a USB Wireless Fidelity (WiFi) adaptor and connect to a wireless network. The PiBakery project or searching the internet can give you pointers on how to configure your computer to use this accessory.

Sources

• RaspberryPi.org
• PiBakery.org
• Raspbian.org