Input and Output Overview

Module G06c

Contents

• Basics of Input and Output
• Input Devices
• Output Devices
• Multimedia

About this document...

Basics

Input:

Any information going into the computer

Output:

Any information going out of the computer

Why?

Computers would be useless without it!

I/O:

Input/Output

Some common input devices

• Keyboard
• 101-key enhanced - standard on full-size computers
• 84-key (getting obsolete)
• Portable computer keyboards (smaller and less convenient)
• Music keyboards can be used to put music in a computer!
• Musical Instrument Digital Interface = MIDI translates music to computer code
• Pointing devices
• Standard mice (roll them around on the pad)
• How many buttons? 1, 2, or 3
• Trackballs (roll a ball around to move a pointer)
• Some people find them easier to use than a mouse
• Need less space
• Often come with laptop computers
• Light pen - point to the screen and push a button
• Joystick - often used for games
• Graphic tablet - lets you point very precisely; used with drafting programs ($$$)
• Scanners - used to bring visual material in
• Graphic scanners
• Color or monochrome
• Hand-held or flatbed; special purpose such as slide scanners
• Reading images vs. Reading characters
• All popular scanners can bring in pictures
• Even text (writing) is treated like a picture
• Special software is needed to translate graphics to text for word processing
• This software is called OCR = Optical Character Recognition
• Fax machines
• Fax machines do graphics scans of pages and transmit the picture
• With a Fax Modem a computer can send a fax or receive a fax and store it as a picture
• If you want to put the fax into a word processor, OCR software is needed. Bar-code scanners
• Grocery store, factory, or post office
• Several bar codes exist: UPS, 5-of-9, USPS, and others
• Other computers
• Computers can talk to each other over wires
• To use telephone wires, a modem is used to convert computer signals into phone signals
• Computers can also be wired together directly to form a network and talk to each other

• Voice command
• A few voice command systems are available that work fairly well
• They require a fast, powerful computer with special sound-capture equipment and software
• Each user has to "train" the computer to recognize his or her words
• Today's systems require separate words - normal speech is too much for them!

• Sensors
• Any device that measures something and sends a variable voltage...
• Thermometer, microphone, video camera...
• The variable voltage is sampled at regular intervals
• The voltage level of each sample is stored as a number by the computer
• This is called analog-to-digital conversion
• Sensors can be used for several purposes...
• Representing nature in the computer (photographs, sounds, weather records...)
• Sensing things that need to be controlled (speed, position, temperature...)
• Controlling a computer in special ways (sensing eye movement, or even brain waves)
• ???
• ...what will they think of next?

Some common output devices

• Monitor screen
• CRT = Cathode Ray Tube (works like regular TV image)
• Bright image
• Requires line-voltage (not battery)
• Bulky
• Good for desk-top computers
• LCD = Liquid Crystal Display (also used in watches)
• Needs to be lit up from behind (usually)
• Low voltage (battery OK)
• Light-weight flat panel
• Good for portable computers and projector displays
• Types of monitors
• Monochrome (B/W) vs. Color
• How many colors? 4...16...256...16.7 million
• How fine is the detail (= "resolution") ? 640 x 480.....1024 x 768.....

Discussion: Which type of monitor do you think will be most common in ten years - CRT or LCD?

• Printers
• Dot matrix
• Pops pins out at the paper using a ribbon
• Resolution (detail): moderate
• Most are fairly slow
• Most are noisy
• Most are cheap
• Ink jet
• Sprays ink at the paper
• Resolution: high
• Most are fairly slow
• Quiet
• Fairly inexpensive (mid-range)
• Laser
• Works like an electrostatic copier (Xerox® type)
• Resolution: high
• Generally pretty fast
• Quiet
• More expensive

• Other computers - networking 

• Motors and Movers
• Robots
• Guided vehicles
• Sound (noise, voice & music)
• General purpose sounds
• Built-in speakers (pretty humble sound!)
• Add-on speakers via "sound card" circuit board

Sound Blaster®, Disney®, or other standard
• Music compositions
• MIDI output to synth
• ??? - What next?

Multimedia - I/O for today's well-equipped computer

• Multimedia: sight and sound under the control of the computer

• Input and storage devices
• Mouse
• CD-ROM (Compact Disc Read-Only Memory) - same as audio CD
• Output devices
• Speakers with Sound Blaster® compatibility
• High-resolution video (1024 x 768 at least) with 16.7 million colors, 15-inch diagonal size minimum
• Good option: video display processor (MPEG or Indeo®)
• Computer:
• Intel 486sx 33 with 8 Mb RAM minimum running Microsoft Windows® 3.1
• Motorola 68040 with 12 Mb RAM minimum running Macintosh System 7.x

Audience:

Objectives

• Define the terms input and output
• Identify the common types of input devices
• Identify the common types of output devices
• Define multimedia
• Identify equipment needed to support multimedia

About this document...

Module G06c: Input and Output Overview

Author:

Laurence J. Krieg

Institution:

Department of Computer Information Systems, Washtenaw Community College

Date:

Written 2 Feb 1988

Revised 2 Mar 1995
HTML version 19 Jan 1996; minor revisions 20 May 1996; Review added 5 Feb 1999
Review:  G06cr