INPUT & OUTPUT! - II

A schematic or block diagram is an overall picture of a machine, ignoring the details. Later, we will look at what is inside each block in my next articles to come.

a computer is a wonderful machine, but it should not be forgotten that it is a machine. the users inputs should be specific, and what the output is depends on the input. If the novel writer types in neatly double spaced gibberish! If the mathematician gives the computer an incorrect equation, the answers generated will not make sense. Computer programmers have a term for this know as "garbage in, garbage out". In other words, the computer won't do your thinking for you. if you even enter in a comma at the wrong place, you may get completely wrong results.

The most common input device is the keyboard. It has all the standard typewriters keys plus a few additional ones. The keyboard may be built in which the processing unit as in the laptops, or attached to it by a cable, as in the normal home PC's. The standard output device is the monitor. A ordinary TV is used instead of a monitor on some smaller personal computers. The user types at the keyboard and the monitor displays what he has typed as well as the computer responses.

Another input device is the mouse, so called because the device with it's attaching cable looks like a mouse with a tail. When a mouse is attached to a computer, a cursor appears on the monitor screen. You can then use the mouse to point to any of the choices available and thus select what you want the computer to do. This is much simpler than typing things out explicitly on the keyboard. Recent computer models use a stylus to write directly on screen and can eliminate the keyboard altogether. Artwork and photograph can also be input into a computer using a scanner.

What appears on screen will disappear if the computer is switched off. Printers are used for more permanent output on paper. They come in varieties, depending on the technology used. Each letter formed by a dot matrix printer is a patter of small dots. Daisy wheel printers are like electronic typewriters. Dot Matrix printers are fast. The can print upto 300 characters per second. Such a printer will take only 7 seconds to print this article. More expensive are laser printers, which print a page of beautifully formed text at a time, instead of printing character by character. Laser printer are also capable of printing drawings or graphics. Architects and engineers wanting precise diagrams use a device called plotter.

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