Input And Output Device Of Computer : Computer Capsule.

Difference between Input and Output Devices

Input and output devices perform two types of operations in a computer system.

Input is any data that we send to a computer for processing. That can be an image from a Digital Camera, or some letters types via keyboard in a word document.

Output is the result of the input data we can see through some output device like a picture displayed by the Monitor, a word documented printed by a printer etc.

3.1 Input Devices

An input device feeds data to the computer system for processing.

We are going to discuss the most commonly used input devices in this article.

Keyboard

The computer keyboard is used to enter text information into the computer. The keyboard can also be used to type commands directing the computer to perform certain actions. Commands are typically chosen from an on-screen menu using a mouse, but there are often keyboard shortcuts for giving these same commands.

In addition to the keys of the main keyboard (used for typing text), keyboards usually also have a numeric keypad (for entering numerical data efficiently), a bank of editing keys (used in text editing operations), and a row of function keys along the top (to easily invoke certain program functions).

Mouse

A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface.

Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail.

As you move the mouse, the pointer on the display screen moves in the same direction. Mice contain at least one button and sometimes as many as three, which have different functions depending on what program is running. Nowadays, mice also include a scroll wheel for scrolling through long documents.

It was Invented by Douglas Engelbart of Stanford Research Center in 1963.

Joystick

Joysticks and similar game controllers can also be connected to a computer as pointing devices. They are generally used for playing games, and not for controlling the on-screen cursor in productivity software.

Scanner

A scanner is a device that images a printed page or graphic by digitizing it, producing an image made of tiny pixels of different brightness and color values which are represented numerically and sent to the computer. Scanners not only scan graphics, but they can also scan pages of text.

Touch Pad

Most laptop computers today have a touch pad pointing device. You move the on-screen cursor by sliding your finger along the surface of the touch pad. The buttons are located below the pad, but most touch pads allow you to perform “mouse clicks” by tapping on the pad itself.

Touch pads have the advantage over mice that they take up much less room to use. They have the advantage over trackballs (which were used on early laptops) that there are no moving parts to get dirty and result in jumpy cursor control.

Trackball

The trackball is sort of like an upside-down mouse, with the ball located on top. You use your fingers to roll the trackball, and internal rollers (similar to what’s inside a mouse) sense the motion which is transmitted to the computer. Trackballs have the advantage over mice in that the body of the trackball remains stationary on your desk, so you don’t need as much room to use the trackball. Early laptop computers often used trackballs (before superior touch pads came along).

Track Point

Some sub-notebook computers (such as the IBM ThinkPad), which lack room for even a touch pad, incorporate a trackpoint, a small rubber projection embedded between the keys of the keyboard. The trackpoint acts like a little joystick that can be used to control the position of the on-screen cursor.

Touch Screen

Some computers, especially small hand-held PDAs, have touch sensitive display screens. The user can make choices and press button images on the screen. You often use a stylus, which you hold like a pen, to “write” on the surface of a small touch screen.

Microphone

A microphone can be attached to a computer to record sound (usually through a sound card input or circuitry built into the motherboard). The sound is digitized—turned into numbers that represent the original analog sound waves—and stored in the computer to later processing and playback.

Graphics Tablet

A graphics tablet consists of an electronic writing area and a special “pen” that works with it. A graphics tablet allows creating graphical images with motions and actions.

The pen of the graphics tablet is pressure sensitive, so pressing harder or softer can result in brush strokes of different width.

MIDI Devices

MIDI (Musical Instrument Digital Interface) is a system designed to transmit information between electronic musical instruments.

A MIDI musical keyboard can be attached to a computer and allow a performer to play music that is captured by the computer system as a sequence of notes with the associated timing (instead of recording digitized sound waves).

3.2 Output Devices

An output device shows data that are processed by the computer system.

Monitor

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.

1. Cathode-Ray Tube (CRT)
2. Flat- Panel Display

A. Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity, or resolution. It takes more than one illuminated pixel to form whole character.

There are some disadvantages of CRT:

• Large in Size
• High power consumption

B. Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT.

You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, graphics display.

Printers

Printer is an output device, which is used to print information on paper.

There are two types of printers:

1. Impact Printers
2. Non-Impact Printers

A. Impact Printers

The impact printers print the characters by striking them on the ribbon which is then pressed on the paper.

Characteristics of Impact Printers are the following:

• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image.

These printers are of two types

1. Character printers
2. Line printers

a. Character Printers

Character printers are the printers which print one character at a time.

These are further divided into two types:

1. Dot Matrix Printer(DMP)
2. Daisy Wheel

i. Dot Matrix Printer

In the market one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character that is why it is called Dot Matrix Printer.

Its speed is measured in CPS (Character Per Second).

ii. Daisy Wheel

Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower name) that is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices which require a few letters to be sent here and there with very nice quality.

b. Line Printers

Line printers are the printers which print one line at a time.

These are of further two types

• Drum Printer
• Chain Printer

i. Drum Printer

This printer is like a drum in shape so it is called drum printer. The surface of drum is divided into number of tracks. Total tracks are equal to size of paper i.e. for a paper width of 132 characters, drum will have 132 tracks.

Drum printers are fast in speed and can print 300 to 2000 lines per minute.

ii. Chain Printer

In this printer, chain of character sets is used so it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.

2. Non-impact Printers

Non-impact printers print the characters without using ribbon. These printers print a complete page at a time so they are also called as Page Printers.

Characteristics of Non-impact Printers

• Faster than impact printers.
• They are not noisy.
• High quality.
• Support many fonts and different character size.

These printers are of two types

1. Laser Printers
2. Inkjet Printers

A. Laser Printers

These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.

B. Inkjet Printers

Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

They make less noise because no hammering is done and these have many styles of printing modes available. Colour printing is also possible.

Plotters

A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens. Unlike a regular printer , the plotter can draw continuous point-to-point lines directly from vector graphics files or commands.

Projector

A projector or image projectoris an optical device, which projects an image (or moving images) onto a surface, commonly a projection screen.

Speakers

Speakers are one of the most common output devices used with computer systems. Some speakers are designed to work specifically with computers, while others can be hooked up to any type of sound system.

Regardless of their design, the purpose of speakers is to produce audio output that can be heard by the listener.