A Typical computer
The computer case is also called the system unit. It contains the most important part of the system, the central processing unit (also called CPU) or brain of the computer. You cannot see the CPU unless you open the system unit. The system unit also contains other parts, many of which can be seen only when the case is opened. The floppy disk drive and compact disk drive may be seen from the outside. Some cases lie flat on the desk, usually under the monitor. Others called tower cases stand upright, either on the desk or on the floor.
The monitor- the monitor is a device that displays text and images generated by the computer. It is sometimes called a visual display unit or VDU. The screen is the display area of the monitor. At the front of the monitor, below the screen, you will most likely find buttons to control the size, brightness and contrast of the on screen display.