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The computer system has four basic components. Input devices accept data (plural form datum). These data are kept in the memory of the computer in storage for later use. Processing of these data takes place in the computer. Finally, results flow through output devices.

Now, we have placed the computer in another perspective. As you will note, the computer is only one of the four major components of the computer system. The computer is primarily responsible for the processing of data and is technically referred to as the processor of the computer system.

As an integral part of the computer system, the computer or processor may be likened to the brain of the human body -- the source of our intelligence – acting in harmony with the other parts of the whole system.


Holds additional data
and programs.
INPUT DATA                                                                                                                                                      OUTPUT Device

Accepts data and sends Releases processed data

data into the computer (information)

or processor.


Accepts data and performs instructions.
(Primary) STORAGE Device
Holds data and programs.


Input Devices


Input devices act like the "eyes and ears" of the computer system. They accept data in a form that the computer can use and sent these data to the computer or processor.

Data are usually entered by the user through input devices which include keyboards, joy sticks and scanners.

The keyboard is the primary input device for the computer systems. The layout of the keys resembles that of a typewriter, but special keys and the function keys, among others, have been included. The function key initiates special operations on data. The function keys’ tasks are determined by the program loaded into the computer.

Although the keyboard is used most often for data input, other devices can be attached to the computer for the same purpose. One popular input device is the mouse. The mouse, a hand-held object that is pushed around a desktop, is essentially a pointing device that allows users to do many operations more quickly than they could with the keyboard alone.

               mouse                                                                 keyboard



Scanners are devices that can scan visual images or text, and convert them to electronic pulses that can be processed and displayed by output devices like the screen or printer.





As mentioned earlier, the processor may be likened to the brain of the human body which is responsible for processing what our eyes see, what our ears hear, and what our skin feels.

The processor accepts data from input devices. The processor contains the electronic circuitry to manipulate data and helps carry out instructions or commands, in order to perform various tasks.

Sometimes, data are sent to storage or retrieved from storage during processing. The processor is contained inside the case that houses the personal computer.

The processor actually transforms data into information. Data are the raw materials which the computer can "process" into something meaningful and useful. "Processed data" that are meaningful and useful to the end-user are referred to as information.


Output Devices

Output devices display, or show, processed results in a form we can use or work with, like a printout or a picture on a screen. Output is the end result of what the computer is all about : to produce information that is meaningful and useful out of seemingly senseless data.

The most common output devices are monitors and printers. But there are other output devices used for special tasks such as over-head projectors, plotters, and speakers. Sophisticated electronic devices are also used as output equipment for engineering (design and simulation), research, and specialized medicine.

Monitor. Screens or monitors show temporary results generated by the program being run on the computer. These temporary results are referred to as "soft copies."

Printer. The printer is the most commonly used output device after the monitor. Printers create a permanent copy on paper of results generated by the program being run on the computer. These printouts are sometimes referred to as "hard copies."




          monitor                                          printer



Storage Devices

Storage devices come in two basic forms, the primary storage and secondary storage.

 Primary Storage. Primary storage is commonly confused with the processor because of their close association during the computing process. Primary storage is also known as memory. Primary storage or memory holds input data before it is processed. It also holds the data after it has been processed but before it is released to any output device. In addition, the primary storage also, contains the programs needed by the processor.

Like the processor, the primary storage stores letter, numbers, and special characters. It can also hold images and sound in digitized form. Primary storage, or computer, memory, has a distinct disadvantage: it holds data only temporarily. Turning the computer "on" activates it, but turning the computer "off" causes everything to disappear.


Secondary Storage. For longer periods of storage, secondary storage devices are used. Secondary storage devices offer not only longer storage time but also bigger capacity to hold data. The most common secondary storage media widely used today are the magnetic disk and the magnetic tape.


Magnetic Disk. The diskette is the most common form of magnetic disk. The diskette is small and practical to use. Because it is made of thin and flexible plastic, the diskette is also called a "floppy disk". Too sizes of diskettes are available : the 5.2-inch diameter diskette and the high-density 3.5-inch diameter diskette. Both are enclosed in a holder that is removable and transportable.

The 3.5-inch diskette, however, is more popular because of its rigid case and higher storage capacity. Disk drives are the primary storage technology utilized by microcomputer systems. Disk drives "read" data from the computer into magnetic disks for permanent storage.

Magnetic Tape. An inexpensive form of secondary storage device. Magnetic tapes come spooled on a reel or cartridge, very much like the cassette tape you are probably familiar with. Magnetic tape reels are installed in tape drives for computer operation where it can be "read" by the computer, or when fresh data are to be "written" on the tape. Magnetic tapes are often used for back-up purposes.


  3.5-inch                                     5.25-inch


compact disk