The first step to building a computer is acquiring the parts. This guide will
start with a quick explanation of essential parts and elaborate on them further
on.
A computer is made up of a case, also called a chassis, which houses several
internal components, and the external components, including peripherals.
Inside the case go the following internal parts:
• Power Supply/PSU power supply unit, converts outlet power, which
is alternating current (AC), to direct current (DC), which is what the
internal components require, as well as providing appropriate voltages
and currents for the various internal components.
• Motherboard/mainboard As the name indicates, this is the electronic
centerpiece of the computer, everything else connects to the motherboard.
• Processor/CPU central processing unit, the “brain” of the computer,
most actual computation takes place here.
• RAM random access memory, the “short-term memory” of a computer,
used by the CPU to store program instructions and data upon which it is
currently operating. Data in RAM is lost when the computer is powered
off, thus necessitating a hard drive.
• Hard Drive/Hard Disk the “long-term memory” of the computer, used
for persistent storage i.e. the things stored on it remain even when the
computer is powered down. The operating system, and all your programs
and data are stored here.
• Optical Drive device for reading/writing optical disks. May read CDs,
DVDs, or other optical media, depending on the type. It is essential for
installing many operating systems and programs. It may be able to write
some of these discs, as well. Some people like to have two such drives for
copying disks.
• Video Card/Graphics Card/GPU does processing relating to video
output. Some motherboards have an “onboard” GPU built in so you dont
need (but may add) a separate video card. Otherwise, you will need a
video card. These plug into a slot on the motherboard and provide a
place to connect a monitor to your computer.
On top of the internal components listed above, you will also need these
external components:
• Keyboard for typing on. Many motherboards won’t even boot without
a keyboard attached.
• Mouse for pointing and clicking. Unless you chose a text-based operating
system, you will likely want one of these.
• Monitor This is where the pretty pictures go. They come in many forms,
the most common being CRT and LCD.
These are the parts that a standard PC will use. We are not considering
such esoterica as headless, touchscreen, or voice-controlled systems. You might
want to make a check list (perhaps using a spreadsheet) of parts to use as you go
about your process of research and selection. That way you wont find yourself
sitting down with a pile of brand new hardware only to find that you forgot an
essential component.
Before you jump onto the web and start spending lots of money on expensive
computer parts, there are three important questions you should answer which
will guide your purchases:

1. What will be the main function of the computer?
2. What useful parts do you have on hand, from an old computer or otherwise?
3. How much can you afford to spend on the system?