What is case and power supply unit?

Casing:

The PC consists of a central unit( referred to as the computer) and various peripherals. The computer is a box, which contains most of the working electronics. Is is connected with cables to the peripherals. Here is a picture of the computer.

Casing

Casing is the outer look of the CPU box. Selecting the case unit is mostly a matter of deciding for a style. In broad terms there are two types of cases:
Desktop Model (Flat)
Tower Models

Both types of cases vary by size and profile. Whereas the desktop case sits (as the name implies) on the desktop, the tower case is designed to stand upright and can be much larger.
Before choosing the case we should think about our location requirements for computer. If we need a simple office machine then we might decide for a desktop style. If, however, we want to keep our options open for upgrading the computer at a later stage, maybe by adding more hard drives or other devices, then we might consider a tower with more room for add-ones.

Uninterruptible Power Supply (UPS):

We know that, computer is an electronic device so electricity is compulsory requirement to operate it. Each and every components of computer can sustain a fixed current capacity so; fluctuation of voltage may damage these components. That’s why; we have to use UPS, Volt Guard, Stabilizer etc. to maintain the voltage fluctuation.
UPS is a device that stores the electricity and supply to the computer automatically  incase of electricity failure. It is used in computer to prevent the loss of data and damage of computer parts caused due to electricity failure.




Uninterruptible Power Supply (UPS)