Computer Base Unit or The Computer System Unit

The system unit is the box-like case that contains major computer’s electronic components (usually excluding the display, keyboard and mouse) which many people erroneously refer to the CPU. The system unit is sometimes called computer chassis, cabinet, box, tower, enclosure, housing, system unit or simply case.

These are some of the major components you are going to find inside your system unit. If you think of checking these components, make sure you power off your computer and disconnect it from the mains. Then locate the top lid of your system unit and remove it so that you can access the inside of your base unit. Be careful not to mess with your components if you are not very familiar with them.

Motherboard

The motherboard is sometimes called the system board or main board. It is the main circuit board of a microcomputer. The motherboard contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive.

When you are reading about motherboards you can not fail to come across the term motherboard form factors, which describes its general shape, the type of case and power supply it can use, and its physical organization (layout of the motherboard).

A hard disk drive is a high capacity non volatile magnetic data storage media with a volume (disk) which is usually non-removable. Data is magnetically read and written on the platter by read/write heads that float on a cushion of air above the platters.

Short for floppy disk drive (FDD), it is a disk drive that can read and write floppy disks although they are obsolete nowadays.

Floppy disk drives have been replaced by the USB flash disk drives.

The power supply unit (PSU) is used to convert AC current from the mains supply to the different DC voltages required by various computer components. Standard power supplies turn the incoming 110V or 220V AC (Alternating Current) into various DC (Direct Current) voltages suitable for powering the computer's components.

Power supplies are quoted as having a certain power output specified in Watts, a standard power supply would typically be able to deliver around 350 Watts.

The more components (hard drives, CD/DVD drives, tape drives, ventilation fans, etc) you have in your PC the greater the power required from the power supply.

It is a high capacity optical data storage device with a removable disk, it writes data onto or reads data from a storage medium. A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, S-ATA, Firewire, or USB interface or a proprietary interface.