The system unit is the most important piece of hardware in your computer system. It houses your computer's brain, disk drives, and many other components which makes it the "mother ship" of your system.
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Desktops and Laptops
A laptop or notebook computer differs from a desktop unit in that it combines all the various elements (except for a printer) into a single case and then adds a battery so you can use it on the go.
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Front and Back
The front of the system unit is where you insert CDs, DVDs, and other types of storage media. The back of the system unit is where all the other parts of your computer system connect.
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Connecting Ports
Every component you plug into your system unit has its own unique type of connector, so you have an assortment of different jacks called ports in the computer world.