Introduction to Computing Lecture-2-Input/ Output and Storage Devices Muhammad Hafeez Department of Computer Science GC University Lahore

Today’s Agenda Input devices Understanding of Input devices Output devices Understanding of Output devices Storage devices Understanding of Storage devices

I/O Devices Input/ Output devices commonly called I/O devices are used to interact the CPU with outside world I/O devices also called peripheral devices

Types of Input Devices Keyboard Devices Point-and-Draw Devices Mouse Trackball Joystick Electronic Pen Touch Screen

Types of Input Devices

Types of Input Devices

Types of Input Devices Data Scanning Devices Electronic-card Reader Image Scanner Optical Character Reader (OCR) devices Optical Mark Reader (OMR) Bar-Code Reader Magnetic-Ink Character Recognition (MICR) Digitizer Electronic-card Reader Speech Recognition System Vision-Input System

Input Devices Keyboard: A 101-key QWERTY keyboard Point-and-Draw Devices When input medium shifted from text to GUI researchers find point-and-draw devices more convenient to point and icons and draw lines, curves on screen. Few point-and-draw devices are: Mouse: A small pointing device fits in user palm. Most convenient and must have for today’s GUI interface Mechanical and Optical Mouse One, Two or Three Button Mouse Wired or Cordless Mouse

Input Devices Point-and-Draw Devices Trackball: Ball is moved with hand, device does not mode Joystick: Used to play games, a stick is mounted on top of device Electronic Pen Touch Screen: A device provide input to the computer using touch of hand. Hand touch is monitored using sensors. Information Kiosk An unattended system at public place to help users.

Input Devices Point-and-Draw Devices Trackball: Ball is moved with hand, device does not mode Joystick: Used to play games, a stick is mounted on top of device Electronic Pen Touch Screen: A device provide input to the computer using touch of hand. Hand touch is monitored using sensors. Information Kiosk An unattended system at public place to help users such as ATM

Input Devices Data Scanning Devices Input devices that enable direct entry into computer from documents Eliminate the need of manual entry by human, reduce error in entry Improve data accuracy and fast processing of information Only high quality documents can be processed, however, work is in progress where lower quality documents can also be entered Form design and ink selection becomes important

Input Devices Data Scanning Devices Image Scanner: translate paper document into electronic format. Input paper may be text, image or picture. Useful for preserving documents. Scanned documents can be changed using image-processing software. Flatbed scanner Hand-held scanner Limitations: No word processing can be done. More storage is required to store images than text and numbers

Input Devices Data Scanning Devices Optical Character Recognition: The scanner is equipped with Character Recognition software called OCR s/w. It converts scanned document into equivalent ASCII characters. Scanner first read image then OCR software converts into character, numbers and special characters. OCR software are complex, as the machine is limited to recognize characters, hence, special OCR fonts are used.

Input Devices Data Scanning Devices Optical Mark Reader: A scanner that can recognize a pre-specified mark by pencil or pen. Bar-Code Reader: A scanner used to read vertical lines on products called bars. Convert bars into alpha-numeric values. Universal Product Code UPC is widely used bar-coding system. RFID: tagged devices, do not require direct or line-of-sight interaction

Ergonomics An applied science devoted to incorporate comfort, efficiency and safety into design of items in workplace

Ergonomically Designed Workplace

Output Information out of Computer System after processing the data is called output. Output can be of the form: Text Graphics Audio Video Also classified as: Softcopy Hardcopy

Output Devices Display Display Technologies: Flat panel display LCD devices lit through backlight Backlight source could be: CCFL (Cold Cathode Fluorescent Lamp) LED (Light Emitting Diodes) LED is light, thinner, brighter but expensive LCD produce color using active-matrix or TFT (thin-film transistor) a separate transistor for each liquid crystal cell, high quality video

Output Devices Display Display Technologies: OLED (Organic LED) technology, organic molecules have the capability to not use backlight and lit themselves Retina Display Technology or AMOLED (active matric OLED) used to view picture from various sides

Output Devices Display Display Quality: Resolution (1600x900) Response Time (turn pixel on/off , 2-16ms) Brightness (measured in nit) Dot pitch (distance in mm between pixels, 0.3 mm) Contrast ratio (difference in lightest white and darkest black, 500:1 to 2000:1, higher ratio represent better colors)

Output Devices Printer Impact Printers: Dot-Matrix Non-Impact Printers: Ink-jet , Laser

Output Devices Laser Printer: Combine a laser, high voltage, charged ions, powdered ink, heat and paper A photo sensitive imaging drum “painted” with a laser Laser prints character on drum This drum also transfers toner to the paper

Output Devices Laser Printer: Toner do not touch the paper, we have to use heat to make tiny particle of powder to produce characters on papers A photo sensitive imaging drum “painted” with a laser Laser prints character on drum This drum also transfers toner to the paper Speed: 4 to 50 ppm

Laser Printer

Laser Printer

Laser Printer

Laser Printer

Laser Printer

Ink-Jet Printers

Ink-Jet Printers

Impact Printers Use mechanism to physically press ribbons on paper to create the desired character Dot Matrix Printer

Dot Matrix Printer Printer characters a pattern of dots Print many special characters and graphics Can be used to generate multiple copies Slow, 30 – 600 cps Cheap in both, initial cost and cost of operation Speed: 1 to 20 ppm

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