1.6 INPUT-OUTPUT DEVICES

In this section you will get introduced with the various types of I/O devices available for computer systems. The topics discussed here briefly will be taken up in detail in the Unit 3 of this block.

The input-output (also known as I/O) devices provide the means of communication between the computer and the outside world. They are also known as peripheral devices because they surround the CPU.

Without any input devices a computer would simply be a display device and not allow users to interact with it, much like a TV.

When using a computer, you must send commands to the computer, and data to be processed. Also, data must be returned from the computer to the user. In order to do this, the computer makes use of input and output devices.

• Input devices (such as keyboard, mouse, joystick etc.) are used to enter data into primary storage (or primary memory) or a hardware device that sends information into the CPU.

The Table 3 highlights the categories of which the input devices.


 Output Devices

The output generated by a computer can be transmitted to the user via some devices or media. These devices are called output devices. The following are some examples of different types of output devices commonly found on a computer. 

Monitor

Printer

Sound card & Speakers

Video card

Plotter

Monitor (or screen) is also called a video display unit (VDU) that displays both input and output data. It consists of CRT (Cathode Ray Tube) technology. It is basically electronic “gun” which shoots (emits) the beam of electrons and illuminates the pixels on the screen.

There are two broad categories of Printers i.e., Impact & Non impact printers. Impact printer uses  striking action to press carbons against a paper to create a character. Dot Matrix printer and Inkjet printer are some examples of impact printer. The term DOT matrix refers to the process of placing dots to form an image. The quality of the image is determined by the dots per inch.

Inkjet printer forms text and/or images by spraying streams of quick-drying ink on paper. The ink is stored in disposable ink cartridges; often a separate cartridge is used for each of the major colors. These colors are usually Black, Red/Magenta, Green/Cyan, and Yellow (CYMK). Today, dot matrix printers are not commonly used or found because of the low quality print outs, when compared to ink jet printers or other later printer, technologies. A Non impact printer such as laser printer uses a laser technology to print images on the paper. Laser printers are often used in corporate, school, and other environments that require print jobs to be completed quickly and in large quantities.

A Sound Card (also known as a sound board or an audio card) is an expansion card or integrated circuit that provides a computer with the ability to produce sound that can be heard by the user.

A Speaker is basically a hardware device connected to a computer's sound card that outputs sounds generated by the card.

Plotter is used in engineering and architectural drawing. It uses a computer driven pen for creating blacks and white or color graphic images like charts, graphs etc.

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