Input and output devices

1. Introduction

1.1 Definition:

A computer is an electronic machine that

1) takes in data and instructions (input)2) works with the data (processing)3) puts out information (output)

or

“General purpose machine, commonly consisting of digital circuitry, that accepts (inputs), stores, manipulates, and generates (outputs) data as numbers, text, graphics, voice, video files, or electrical signals, in accordance with instructions called a program.”

Computers are not very intelligent devices, but they handle instructions flawlessly and fast. They must follow explicit directions from both the user and computer programmer. Computers are really nothing more than a very powerful calculator with some great accessories. Applications like word processing and games are just a very complex math problem.

1.2Software and Hardware

If you use a player piano as an analogy, the piano can be thought of as the hardware and the roll of music as the software.

The software a series of very simple computer instructions carefully organized to complete complex tasks. These instructions are written in programming languages (like BASIC, PASCAL, C...) to help simplify the development of applications.

The hardware is what sits on your desk and executes the software instructions. The player piano is useless unless the roll of music has been written correctly.

1.3Hardware Components

Input Devices -- "How to tell it what to do"

- A keyboard and mouse are the standard way to interact with the computer. Other devices include joysticks and game pads used primarly for games.

Output Devices -- "How it shows you what it is doing"

- The monitor (the screen) is how the computer sends information back to you, whether it be surfing the web or writing a memo. A printer is also an output device.

Storage Devices -- "How it saves data and programs"

- Hard disk drives are an internal, higher capacity drive which also stores the operating system which runs when you power on the computer.

2. Input devices

An input device is any device that provides input to a computer. There are dozens of possible input devices, but the two most common ones are a keyboard and mouse. Every key you press on the keyboard and every movement or click you make with the mouse sends a specific input signal to the computer. These commands allow you to open programs, type messages, drag objects, and perform many other functions on your computer.Since the job of a computer is primarily to process input, computers are pretty useless without input devices. Just imagine how much fun you would have using your computer without a keyboard or mouse. Not verymuch. Therefore, input devices are a vital part of every computer system. There are many forms of input devices such as:

2.1 Keyboard

The keyboard is a way to input letters or numbers into different applications or programs. A keyboard also has special keys that help operate the computer.

2.2 Mouse

The mouse is used to open and close files, navigate web sites, and click on a lot of commands (to tell the computer what to do) when using different applications.

2.3 Joystick

A joystick is used to move the cursor from place to place, and to click on various items in programs. A joystick is used mostly for computer games.

2.4 Track ball

A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball.

2.5 Touch pad

A touchpad (or trackpad) is a pointing device featuring a tactile sensor, a specialized surface that can translate the motion and position of a user's fingers to a relative position on screen.

They are a common feature of laptop computers and also used as a substitute for a computer mouse where desk space is scarce.

2.6 Light pen

It is a pen shaped device used to select objects on a display screen. It is quite like themouse (in its functionality) but uses a light pen to move the pointer and select anyobject on the screen by pointing to the object.

2.7 Microphone

A microphone is used to record sound. The sound is then saved as a sound file on the computer.

2.8 Digital camera

A digital camera can be used to take pictures. It can be hooked up to a computer to transfer the pictures from the camera to the computer. Some digital cameras hold a floppy disk, and the floppy disk can be taken out of the camera and put directly into the computer.

2.9 Scanner

A scanner is used to copy pictures or other things and save them as files on the computer.

3. Output devices

Any device that outputs information from a computer is called, not surprisingly, an output device. Since most information from a computer is output in either a visual or auditory format, the most common output devices are the moniter and speakers. These two devices provide instant feedback to the user's input, such as displaying characters as they are typed or playing a song selected from a playlist.

While monitors and speakers are the most common output devices, there are many others. Some examples include headphones, printers, projectors, lighting control systems, audio recording devices, and robotic machines. A computer without an output device connected to it is pretty useless, since the output is what we interact with. Anyone who has ever had a monitor or printer stop working knows just how true this is. Of course, it is also important to be able to send information to the computer, which requires an input device.

3.1 CRT Monitor

Monitor is an output device that resembles the television screen and uses a CathodeRay Tube (CRT) to display information. The monitor is associated with a keyboardfor manual input of characters and displays the information as it is keyed in. It alsodisplays the program or application output. Like the television, monitors are alsoavailable in different sizes.

3.2 Flat pannel monitor

encompass a growing number of electronic visual display technologies. They are much lighter and thinner than traditional television sets and video displays that use cathode ray tubes (CRTs), and are usually less than 100 mm (4 in) thick. They are thin and light. They provide better linearity and higher resolution.

3.3 Printer

Printers are used to produce paper (commonly known as hardcopy) output. Based onthe technology used, they can be classified as Impact or Non-impact printers.Impact printers use the typewriting printing mechanism wherein a hammer strikesthe paper through a ribbon in order to produce output. Dot-matrix and Characterprinters fall under this category.

3.4 Plotter

Plotters are used to print graphical output on paper. It interprets computer commandsand makes line drawings on paper using multicolored automated pens. It is capable ofproducing graphs, drawings, charts, maps etc.

3.5 Speaker and headset

The Audio output is the ability of the computer to output sound. Two components areneeded: Sound card – Plays contents of digitized recordings, Speakers – Attached tosound card.

3.6 Digital light projector

Digital Light Processing (DLP) is a trademark owned by Texas Instruments, representing a technology used in some TVs and video projectors. It is also one of the leading technologies used in digital cinema projection. These rear-projection technologies compete against LCD and plasma flat panel displays in the HDTV market