All external parts of a computer correspond with its many functions, including input, output, processing and memory. The type, size and capabilities of computers are vast and varied, as are their external parts. Depending on the brand of the computer, there can be some differences in size and functionality among the external parts.
According to Microsoft, the system unit of a computer is the central brain and memory of the computer. Traditionally the largest external part of the computer, the system unit originally was called the tower, due in part to its size and shape. As technology improves, system units become smaller and more powerful. New laptops have system units that are barely noticeable. Desktop computers look very different from desktops five years older. Increasingly, towers hold more memory, and are smaller and sleeker. Ports for USB drives, memory cards and other external disk-like devices can be found in the system unit.
The computer monitor is the most interactive external part of the computer. The monitor seems to house all the action, but really it is just a display screen for the system unit. People look at the monitor to read what is on their computer, to type in input and for every other computer-related function. Similar to the system unit, the monitor has also decreased in size. Sleek, new flat-screen monitors have replaced the old bulky boxes. A computer cannot function properly without a working monitor.
Keyboard and Mouse
Keyboards allow input. Information, mainly text and numbers, is input with the keyboard. Similar to a typewriter, a keyboard has letters and numbers but also special keys for different functions (F keys). Some also have accountant-style 10-key number pads that allow for swift calculations.
A mouse is a small optical or trackball device that connects to the system unit through a USB port and moves the cursor on the screen. Although keyboards are equipped with navigation keys (arrow keys), most people prefer the smooth, swift movements of a mouse to navigate across the monitor. Laptops have a touchpad built into their keyboard area for navigation, but a user can connect a mouse if he prefers.
While a keyboard is a critical part of the input process, a printer serves an important role in the output. Printers are not necessary for a computer to function, but they produce the paper documents so integral to communications and recordkeeping. Many printers come with scanner, copier and fax capabilities.
Speakers are one of the output components of a computer. Usually, the computer's internal speakers allow sounds, music and other output functions to be heard, like beeps or error messages. External speakers can also be connected to the computer to provide louder, more distinct sounds.