Overview of the Personal Computer

Overview of the Personal Computer

While most people are familiar with computer software, others also become familiar with the hardware.  Understanding computer hardware can help you understand the capabilities of technology and how the hardware impacts software.  The following sections provide an overview of computer hardware and the role it plays with the software that you use everyday.

Keep in mind that this handout is an overview as there are many different types of any single computer component.  When you shop for components individually or as part of an entire computer, you will hear lots of acronyms and terminology like Core 2 Duo or SLI.  These names come and go as technology evolves.  Here we are discussing what the parts of the computer are at a conceptual level.

CPU

The CPU or Central Processing Unit is like the brain of the computer.  It is in charge of executing instructions as directed by software programs.  The CPU is plugged into the motherboard of the computer, which is explained next.  A CPU is roughly a flat square with a lot of short pins sticking out of the bottom.  CPU’s get very hot and so must be kept cool with fans inside of the computer.

Motherboard

The motherboard is the main component to which all other computer components are connected. A motherboard is as the name implies a flat board that has many computer chips, slots, and ports on it to allow for communication for data input and output with the devices that you attach to the computer. There are many components on a motherboard including:

• The CPU.  The CPU is plugged into a special socket on the motherboard.  There are many types of sockets, with each supporting a different range of CPUs.

• Memory or RAM Slots.  Memory is plugged into the motherboard in a set of slots. There are often 2 to 8 slots on a motherboard and memory is typically installed in pairs. Memory slots are compatible with only one type of memory, such as DDR or DDR2. 

• The Chipset. The chipset is a set of two chips that connect all components on the motherboard to the CPU. They consist of the Northbridge and Southbridge.  The Northbridge connects the CPU to high-speed devices like memory and graphics cards. It also connects the Southbridge to the CPU.  The Southbridge connects to all the slower devices like Ethernet, USB, and audio.

• Rear I/O Ports: These ports are located on the back of the motherboard.  The ports provide connections for input/output devices including, but not limited to the keyboard, mouse, USB, monitor, audio, serial port, and network (or Ethernet) port.  These ports stick out of the computer case and allow you to connect devices to the computer.  Many of these ports have distinct shapes that help determine which devices are plugged in where.  With minor exception it is hard to plug in a device into the wrong type of port. 

• Expansion Slots are used to plug-in various cards to allow you to extend the capabilities of your computer. Devices using these ports include sound cards, video cards, network cards, and many more.  The cards are generally flat, and have several chips on them.  There is a flat connector along the bottom edge of the card that allows you to push the card down so that it is perpendicular to the motherboard.  It is not uncommon for cards to have ports of their own to allow you to connect devices like speakers or monitors to them, depending on the purpose of the card.

• Storage device ports like IDE or SATA ports.  These ports are used to plug in storage devices, most commonly hard drives, and optical drives.

• Some motherboards also have built-in video and audio, but sometimes you need to add your own cards to either supply these capabilities or to upgrade to a better quality of video or audio.

Power Supply

As you know, a computer needs power in order to run.  Every component of a PC has a power requirement. To meet this requirement we need a power supply that can supply enough power to all of the computer’s components.  Power supplies are measured in Watts.  This device is a small box shaped device that is screwed into the computer case.  From the outside of the case, you plug in the power cord and you can press the power switch.  From the inside of the computer case many wires emanate from the power supply.  These wires are connected to devices and in several places along the motherboard to ensure that all components’ power requirements are met.

Fans

The computer generates a great deal of heat and it is important to keep the computer cool so that it does not overheat when it is working on an important task for you.  There are special cooling systems that some people buy, such as water-cooling systems, but most people are content with having fans in the computer case that keeps everything cool.  In older computers the fans can be loud but newer computers have quieter fans.  There are 2 main types of fans:

• Case Fans:  Case fans are screwed into the inside of the computer case.  The case fans are square shaped with a wire sticking out of the top that is then connected to the motherboard.  The computer case determines the size of the case fans.  Older computers had 1 fan, but newer computers often have 2 fans where one fan is drawing air into the case and the other fan is moving air out of the case. 

• A heatsink fan is critical to cooling the CPU as the CPU can overheat.  Older computers may not have a heatsink fan, but nearly all do now.  The heatsink fan consists of two components: the heatsink, and the fan. The heatsink is a large block of metal that is secured on top of the CPU to efficiently draw heat away from the CPU. The fan lies on top of the heatsink.  The purpose of the fan is to cool the heatsink, blowing hot air away from the CPU and ultimately out of the case.  The fan basically looks like a smaller version of a case fan.

Memory

Memory also known as Random Access Memory or RAM is used by a computer to store data that it is currently using.  RAM is very fast, but it needs a constant power supply to hold the information. So once the power is turned off, the memory is erased.  Memory looks like a thin, flat rectangle with several computer chips in it.  There are special connectors on one of the long side’s of the rectangle that inserted into the memory slot.

Hard Drive

The Hard Disk Drive or HDD is used to store data in a more long-term manner as compared to memory. The operating system and all programs are installed on the hard drive. People often store documents on the hard drive as well.  A hard drive is about the size of your hand, but it is rectangular and thicker than your hand.  A hard drive uses magnetic platters to store information in binary form, using ones and zeros.  The platters rotate at a high speed while a read/write head moves over the platters reading and writing data. The heads never touch the platter, as that would scratch them and destroy the data stored on them since they are spinning so fast.  Instead the hard drive is designed so that the read/write head flies just above the surface of the platter.  Because of this delicate design, it is possible for the read/write head to touch the platter if a hard drive is moved while it is on.  The read/write head retracts to a locks position when the hard drive is not on.  There is always at least one hard drive inside of the computer case, but you can have hard drives externally attached to the computer as well.

CD and DVD Drives

CD and DVD drives allow the computer to access files stored on CD and DVD discs.  DVD discs store at least 4 times the amount of data as a CD, depending on the type of DVD format being used.  You can watch DVD movies using the DVD drive, but you can also use the discs for other data.  If you buy a CD or DVD drive that records data, you can write data to these drives.  These drives are the same dimensions as a hard drive, and like a hard drive these drives can be internal to the computer case or externally attached to the case through a port such as USB or Firewire.  Both drives use lasers to read data from these discs.  When a disc is scratched or smudged, it is possible that the laser can’t read the data on a disc properly. 

A Word about Static Electricity

Most people think about static electricity when they shock someone after walking across the carpet or when they are folding their laundry.  But static electricity is an important consideration when working with PC components.  Static electricity or specifically ElectroStatic Discharge (ESD) occurs when a small electric charge builds up and suddenly finds a path to ground and discharges. While this charge is fairly minute to a person, it is enough to damage or even destroy a PC component. When working on the inside of a PC it is vital that you use proper grounding equipment. An example of such items is an anti-static wristband and an anti-static mat. Touching the case does not provide protection for ESD.