Inside the System Unit

The system unit is the box (or laptop body) that holds the main parts of the computer. Monitors, keyboards and printers plug into it, but they are outside it.

System units come in different form factors (sizes and shapes):

• Tower — a tall case with room for many drives and cards. Easy to upgrade.
• Small form factor (SFF) / mini PC — small, quiet, uses less power. Popular in offices and at shop counters.
• All-in-one — the computer is built into the back of the monitor. Tidy, but harder to repair or upgrade.
• Laptop — everything, including the keyboard, screen and battery, in one portable case.

Processors turn electricity into heat. If they get too hot they slow themselves down (thermal throttling) or switch off. Heat sinks, fans and good airflow keep them cool. In a hot, dusty climate, cleaning the dust out of fans once or twice a year helps a computer last longer.