Output Devices are all part of the Hardware

Output Devices are all part of the Hardware of a computer system Output Devices are about seeing the results of your work! Business Studies Stage I Computer Applications Slide 1

Some Output Devices Paper Video Monitor Sound Controlling Other Machines Business Studies Stage I Computer Applications Slide 2

Types of Output • Soft Copy • Hard Copy • Communications Channel Business Studies Stage I Computer Applications Slide 3

Screen Output – Soft Copy • Video Monitor – Also called Video Display Terminal (VDT) – Image exists in video memory—VRAM – Monitor size is measured diagonally across the screen Business Studies Stage I Computer Applications Slide 4

Pixels • Images are made up of dots called pixels for picture elements • The number of pixels determines the clarity of the picture on the screen • More pixels = higher resolution = clearer picture Business Studies Stage I Computer Applications Slide 5

Color Depth (Bit Depth) • This means the amount of information stored in each pixel about what is being shown on the monitor – Monochrome (1 bit of information per pixel) • This can only be black or white – Gray-scale (8 bits of information per pixel) • This can show more shades of grey – True color (24 or 32 bits of information per pixel) • This can realistically reproduce a photograph on the screen that looks very close to the original Business Studies Stage I Computer Applications Slide 6

Examples of Color Depth The greater the color depth the more colours that can be represented on the screen 1 -bit depth 4 -bit depth 8 -bit depth 16 -bit depth Business Studies Stage I Computer Applications Slide 7

Classes of Monitors CRT (cathode ray tube) LCD (liquid crystal display) Business Studies Stage I Computer Applications Slide 8

CRT (Cathode Ray Tube) • A CRT is a television-style monitor • Its features include: – – Clear image Quick response time Low cost Very popular Business Studies Stage I Computer Applications Slide 9

Features of CRT Displays • Display text and graphics • Monitors differ in resolution • Standards – SVGA – 1024 x 768, 1208 x 1024 and 1600 x 1200 – XGA – has same resolutions but supports more colours • Screen sizes vary from 15” to 21” Business Studies Stage I Computer Applications Slide 10

LCD (Liquid Crystal Display) • LCDs comprise flat-panel monitors • Found on watches, calculators, digital cameras and notebook computers – – – Lighter weight Crisp, clear images Extra viewing area for same size More expensive to buy Consume less power Business Studies Stage I Computer Applications Slide 11

Paper Output – Hard Copy • A printer is a device that produces output on paper • Most printers today can produce both text and graphics • Two types of printers: – Impact printers – Non-impact printers Business Studies Stage I Computer Applications Slide 12

Impact Printers • There is some physical contact with the paper to produce the image ie physically striking the paper • Types – Line printers – Dot matrix printers Business Studies Stage I Computer Applications Slide 13

Line Printer • Line printers – Used by mainframes for jobs that need a large volume of printing – Limited characters available – Print an entire line at a time – Cheap to run – Not high quality Business Studies Stage I Computer Applications Slide 14

Dot Matrix Printer • Have a printhead made up of columns of pins – The pins form characters and images as patterns of dots produced when the pins strike the paper – Reasonable quality text and graphics – Inexpensive to buy and run – Noisy Business Studies Stage I Computer Applications Slide 15

Non-Impact Printers • Laser Printers • Ink-jet printers • Bubble-jet printers Business Studies Stage I Computer Applications Slide 16

Laser Printers • Laser printers – Image transferred to paper with a laser beam • Faster and more expensive than dot-matrix • High-resolution output • Expensive to buy • Quite expensive to run Business Studies Stage I Computer Applications Slide 17

Ink-Jet Printers • Ink-jet – Dots of ink are sprayed onto the paper to form the image – Reasonably high quality – Available in colour or B/W – Speed measured in pages per minute – Reasonably priced – Expensive to run Business Studies Stage I Computer Applications Slide 18

Plotters • Used by graphic designers/architects – Image transferred to paper with ink pens – Very high resolution – Excellent for scientific and engineering applications Business Studies Stage I Computer Applications Slide 19

Printing Terms • • • Dots per inch (dpi) Pages per minute (ppm) Characters per second (cps) Laser printers – 50 ppm Ink-jet printers – 12 ppm Business Studies Stage I Computer Applications Slide 20

Output You Can Hear • Synthesizers can be used to generate music and sounds • Many computers have synthesizers • Sound cards have built-in synthesizers Business Studies Stage I Computer Applications Slide 21

Machines Controlling Other Machines • By turning bit information into movements (robots) or measurements (sensors), machines can control other machines: – – Automated factory equipment Telephone switchboards Robot arms Spacecraft Business Studies Stage I Computer Applications Slide 22

Output to a Network – Computer to Computer • Needs a Communications channel • The Internet and WWW • Needs a modem to convert data for transmission across network Business Studies Stage I Computer Applications Slide 23